 Good afternoon, gift teachers and speakers and committee on education. This is the third session of the virtual gift 2022. And I welcome you to a, the continuation of the topics on that we're dealing with on how the planet shapes the history. And we have some very exciting talks and a demonstration today. We have a minute or two before we're scheduled to start and I was thinking that this is conferences being dedicated as a tribute to a our amazing chairperson who Chris was. He was a very humble but he was very passionate about education and outreach to the community and we saw that with all of his ideas and working with him. You know, one of my fond memories of him is being at the IEA and he's on one side of the center and I'm with another group of teachers were both demonstrating a hands on thing. But you know what it also occurred to me that I know that at the beginning we talked about gift itself and European gift as you knew a little bit about this that it was an outgrowth of a idea that came from the AGU where Carlo and I were actually on this committee for the Committee on Education and Human Resources. And while that it never received the kinds of support that the EGU was giving us and you know and I reflected on this yesterday, that are really our, our debt for having such great success because we had far more challenges than we had earlier, you know, as it transitioned over and so I'm talking about going from 2000. I'd like to say 2001 where Carlo and I were working with AGU in San Francisco, and they were a local, they didn't have support from AGU, even getting their registrations paid. And so it was just amazing how little support they got they had donuts and coffee, you know, for breakfast for breakfast and that was about it. And here we have a great debt to the EGU. And I'd like to say it again but our director was such a great enthusiast for education so our 20 years of success, really go back to EGU and the great support that they had, you know, financially, which at the AGU while they continue to have if we have a location for keeping our talks all in order, and you can refer to those and the talks that are going to be recorded today are also going to be available to all of you. And that's something that has never occurred really for the AGU. And so the great success of 20 years, we really owe a debt to the EGU and our director because he was passionate about young scientists and also having the gift workshops. So, while very, very grateful to EGU for our success as with the gift workshops. So today, we are very fortunate to have these three presentations talks this morning. And the focus today is on, I would say that it's more urban environments and, and it's I think cost us you told told me that, you know, for the most part when we look at the earth influence on history of that we talked about the earth, his earth and the cities are really successful. We tend to think about the disasters for the cities, rather than the successes so this is not a meeting about the successes of the earth, but it's more about the disasters and we're going to hear a lot more about that later on. Later on, when we talked about volcanoes and glaciers and other events that shaped the human history. But so this morning in, I'm here in the United States. It's about eight o'clock and and the afternoon for you will involve some discussion and a about seismic and you'll see a hands on activity with Jean Luc. And then we're going to take a short break at about 325 your time. And, and coming back and you're going to hear from Carlo, who is passionate about his exploration of Machu Picchu. And then we'll end the day with young devils on urban geo archaeology in Belgium. So we have a full lineup for you today, and this is being recorded so if you want to go back and refer to the talks. You'll be available starting next week. And with that, I will turn the microphone over to Jean Luc, and for your hands on presentation. Stephen, I needed to to be co host to to be able to share my screen, I guess. I am making you, you are a host. Okay. Okay, I think it's okay. Can you see my screen, I guess, yes. Okay. And I need maybe to. So, Well, let me welcome all of the teacher for this afternoon. Of course, we are going to speak about Rome city in the old time. And mostly we are going to try to make a hands on activity about the seismic site effect illustrated in the city of Rome. Of course. Of course before let me quickly introduce myself because I'm not sure that I know everyone during the meet this meeting where I am teacher so I'm going to speak into present hands on activity using that you can use directly at school so it's the reason why I'm going to show you very simple tools to use at school. I am also leading for a long time now the seismology school network in France. It's also the reason why I am going to show you some hands on activity about seismology. And I am a member of a team education team in a research lab. From the University of Côte d'Azur where I live. And for that reason I am involved today in edumate observatory that is a one of a platform that we are going to use this afternoon during the hands on. So maybe you will have to use with me this this web platform. I am also leading inside education that is the education chapter of a scientist expedition and exploration on Mars. This is a exploration with a seismometer on Mars. So from 2018 the seismometer worked directly in on Mars and we learn a lot about the structure of the red planet. And I am deputy chair of the committee of education of edu. So for today, let us practice as we can with zoom because hands on activity with zoom for me is not very not very fun. And I guess it's the same maybe for you because it will be very nice to practice by yourself. So I'm going to run this session. Step by step. The step one is, I'm going to show you with some slides, the case study. And I'm going to explain the case study with some slide like a presentation. In the second step, we will do together the data mining online in real time. So I will ask to you to do the same thing as I do directly on your computer. It will take a little more time, but I think it's necessary to to practice and so to use the data mining directly by yourself. And for the first step, I will show you some experiments that you can do in the classroom to illustrate this case study. And we will make together some conclusion about the contents of presentation and maybe also for the use of this presentation of this case study in schools. Okay, so as I said before, the hands on workshop is about the seismic site effect. And I'm going to illustrate this topic with the old Roman treasure that we can find. If we go to Rome city, you can see, and you are going to, and you can see this monument. And we will focus on two specific monument, that is two columns. One column is the columns of Mark Aurelius and the other one is the Trian column. They were built in the second century. So, and they are still there in Rome and everyone who visit Rome can see these two columns. So, as I said before, step one, I just show you how to use, how to lead the case study. So, we are speaking about two columns. We are located in two separate points in the city. There are something like 30 meter high and we can see on this column some barrel yes, showing battle scene and groups of enemy defeated during the war fought by the Roman. So, these two columns, you have the photography of these two columns, and we have a photograph of Barrel yes of these two columns. So the construction of this monument required the use of very complex techniques. It was to super in poise, as you can see marble blocks. One marble blocks is something like 40 tones, so it's quite heavy. And they, and it was also to make to coincide perfectly the blocks, one we be over taking in account of two things. The first things it was to taking account of the relief, which were probably probably already sketched and gradually finished during the construction. And the other things it was also to taking in account the interior spiral staircase, which had to be dug into the blocks before they were placed. So it is complex to do. And you can see the two colon, and you can see the two barrel yes. Now, this is my first question. It's a question of observation, I am doing a hands on activities so maybe the first step is to ask question and making some observation. Of course, as I said, I show you things very simple. Examine the barrel yet for this column, you can see an anomaly in one of them. I think you have find it. This marker is colon, you, if you look specifically to the barrel yes, you can see that the shift. So the barrel is coinciding is not coinciding there perfectly. And we guess that at the moment when the colon was made, the barrel yes was completely incorrectly done. So that's mean that shift is younger that the construction of a column something happens to explain this shift. So we have we have not to try to make some hypothesis to explain what happened with this barrel yes. The two columns have the same age. So they are built in the second century. And they are not very far. So the distance between the two columns in in Rome, city is something like 600 meters. And Correus is a little in the north try and is in the south but very, very close. The two columns are very close. And so my hypothesis, one of the hypothesis can be this one. Two days ago, Grant Heiken in the session one spoke about this he spoke about strong earthquakes after the second century in Rome. So if strong earthquakes occurred in that period, they should have affected the stability of the colon. And particularly the cologne of Mark or alias. And so is this fact is very fine. It would be necessary to explain why the try and colon was much less affected by the earthquake. If I compare with Mark or alias. So my hands on activity is to go through this hypothesis and to find some conclusion about this. What about the seismicity in Italy because we are speaking about earthquake. Well, if you collect actually in the seismicity of Italy, you can see that Italy, there is a lot of earthquake in Italy. And you can see in the yellow circle, this is the area of Rome and the larger one home. You can see that earthquakes occurred in this area and strong earthquake can also occur along the Italian country. And so that means that today, Italy know very well seismic event. And in the past, and well, if you, if you look at Twitter, for example, you have news, news after news, and when an earthquake is strong enough, you have a breaking news on ENGV terremotie or ENGV terremotie on Twitter. And you can have some alert, some alarm about an earthquake in that region. As I said, grant icon Monday, I've shown this picture with also what about the past earthquake. And we know that there is, they were also strong earthquake in the past, in the past. And also we know that this earthquakes and he has showed this Monday to this. In the past, we have a lot of damage in the city because of this earthquake. And so our hypothesis can be good. If we according to this, of these things, earthquakes occurred in Italy on the recent time in the past time, and we have also some proxy during directly in the city, when we know that there is a lot of damages because of earthquakes. So, maybe we can explore what happened with the Triane and Mark Aurelius. In fact, because of this, because of this seismicity in Italy, and, and also in the capital town of the city of the country. ENGV has some permanent and non permanent seismic network. You can see on this map. This red mark, this red mark are sensor or seismometer or more exactly accelerometer play located in the city. The number to identify the sensor, it was a number. So you have an hour 25 and 16 and seven and one and you see that the center are located in different place. Along the Tiber River, as you can see here, maybe I'm going to use my, okay, so you can see the Tiber here and we are in Rome City and you have a lot of sensor. So it's completely useful to, to record earthquake, local earthquake, regional earthquake or far away earthquake. So in my example in my case study, we are going to, we are going to study, we are going to study an earthquake that occurred, not very well last last year in Greece. It was a long earthquake, and it was recorded on a lot of sensor, not only in Italy, but we are going to see the record of this earthquake in this red station but I show you on the map. So for this, I need to collect data or to make a data mining on the web to look at the seismogram recorded by the station when occurred this earthquake. For this, I need to go, I need to go to a web platform where I can find this kind of data and to see what is this data can show me some aspect. So this is why I, oops, sorry. So I propose to you, if you are there, I don't know if you are follow me. If there is some difficulties for you to follow me, please ask right in the chat, and then Teresita will, will say to me, will tell me if there is some, some question of some hesitation. But what I would want is that everyone can go directly with this computer, with this computer directly on this web page. So edumad.unis.fr data center slash seismo, and we are going to make the activity directly together, not with a slide but directly on the web. So I'm going to close to share my screen. I come back to you. Jaluc, leave the link a little bit more. Yes. Yeah, I'm going to copy the link in the chat. Okay. Because it will be, it will be easier to, so if you, if you click on the, on this, as I'm, and now I'm going to share my screen to show you the page. So I think you can see the screen now. It's not my slide is directly the website. If someone can tell me if you can see the screen with the webpage. Yes, yes, we can. Good. So this is a French website, but most of them, the most important word are also in English. So what I try to do is to find data. So seismogram about this earthquake occurred in Greece and recorded in Rome. So I'm not looking at this day plot that you can see with me because it's the real time now so I'm just going to select this part. This is seismogram. So I click on seismogram. And I go in that page where there is a French part and the English part. And so I can click on English part. And then I am directly on the website, a list. So you can see the database. If you prefer a list of earthquake with for which we consider but the seismogram are interesting to use at school. So it's seismogram with a pedagogic interest for teachers. And the reason I show you this website because you will maybe you will have opportunity to to explore more and more the data on this website. So I tried to find an earthquake occurred in Greece and recorded in Rome. And it was in March 2021. And I can see this data earthquake occurred in Greece recorded in Rome. I guess everybody can be there. And so now I have to choice download the file in a zip format. So that's mean that I'm going to download data. Without software to analyze data is not very interesting because you are not. Or images you are downloaded the numeric digital file. So that's mean that you need a software to analyze that if you have the software of one software there is a lot of software you can only download the zip file. But if you have not the software I can recommend you to display the data directly with the software and the software is free is directly working on the web. And we call him it tectoglub 3D. So I click on display with tectoglub 3D. And when I do this tectoglub open you have the English version because you were in the English part of the website. And then you are you can see on the left side the map. The map. You have the south of Europe with Italy with Greece. And on the left on the right side you have seismogram. But it's not. Of course it's picture but it's a digital data. For example with my with my mouse. I can enlarge that the seismogram you can see so I can have a zoom directly. And I can also move the seismogram in each direction just to be able to read them correctly. So if I am not very maybe I have to improve the background the scientific background about the seismogram. So we have one earthquake is the red point that you have on the map. The red pond is the epicenter. We know where this earthquake occurred. This is the epicenter in Greece in continental Greece. And the white point and seven. It's the place where we have our seismometer. So if I enlarge the map with my mouse, I can see that this is not one point, but two points I am going to work on two different accelerometer, the number one and the number seven. So we are in Rome, but the map is not very nice. Okay. So you can improve the map asking a satellite image. So on the top of the map, you have a little signal. And if you click on the signal, the map will be directly improved like I have done on my computer. So I think you can find it. So you have a little signal to improve the map because we have made a zoom. So we are in Rome, no trouble with this. We can see the Tiber Valley and we have two accelerometer number seven and number one. They are very close. And they are so close that the two points are completely similar if you according the distance with the Greek earthquake. So that's mean that we can expect that on these two seismometer, we must have the same data because we have the same distance. And it seems that the seismometer are so close that we can imagine that the data, the seismogram will be the ground motion. In this place are the same. So now we are going to look at the seismogram on the right side. I go slowly with you because my objective is that you can follow and that you can do by yourself this. And not only listening a presentation. It ends on activity on zoom so of course I can not help you directly with your computer but I hope you can follow this step. So now I am looking at the seismogram on the right side. On the right side, I can see on the top window, I can see the reference of the earthquake. So that's mean the date, magnitude, depth, epicenter and the red point show the epicenter. And now we have two stations, station NR1, station NR7. The station are completely integrated to the network of ENJV. So I have a localization of this station and I have also the distance between NR1 and NR7. So it's quite the same as 841, 44 km. And after we have for each station, you have three components. So maybe you are not familiar with this, the seismometer records the ground motion in three directions. If you see the letter Z, that means that it is the component which records the vertical movement. So the ground is moving up and down and the component of the seismometer which records this is the number Z, the letter Z. So this record is the vertical movement. If you see E or N, that means that it is the horizontal movement. E means movement motion east to west and N north means north to south. So you can see all the ground motion east to west, it is the first seismogram. South it is the second one and vertical it is the third one. This is for one station for NR1 but if I go below I can see the second one, so for NR7. Okay, so of course I can compare the ground motion in the place of the station number one and the station number seven. But before comparing the seismogram, I must be sure that the scale is the same. The computer doesn't give you the same scale. It's using its parameter to show you in the best way the seismogram. So if you want to compare, you have to fix the same scale. So you have to go below in settings window and you can see in settings window but there is, you have to check and to fix the same scale on axis. And if I do this, now when I fix the same scale for the amplitude, I can see some difference because now I can compare the two seismograms because I am with the same scale. And when I look at this, I see I can compare things very well and I see that something is quite strange. Because if I look at the station number one, the amplitude on each component are very low if I compare with the amplitude of the station number seven. And the stations are at the same place. The station one is closer than to the earthquake to the other one. So the amplitude is lower. So something is wrong. Well, it's wrong because when we are teacher and when we speak to the student, we say that with the distance, the seismic waves propagate and decrease the amplitude, the energy decrease along the distance. And then here, I am not, I have not the same amplitude for this seismogram. So there is something strange. I can improve my lecture, my observation of a seismogram because I have in the new display a lot of information. So you go to seismogram in the menu. So you have file, action, seismogram and data displayed in seismogram. You can display the origin time. So if I do this, I have a green axis. This is the time, this is the date, exactly the date of the earthquake. So of course, the T of the origin time is before the arrival of the waves, but you can also ask to display the waves arrival time. So you have the P waves, the S wave and the longitudinal, the low waves. So that means that you can display the arrival time for the P waves, the S wave. So you see that the P waves, arrival time for the P waves, the S wave is the same. So the amplitude can be explained by something else. So I see that what I compare, I see there is the big difference. And maybe the big difference between the three is the movement north, south. If I look the components north, south for the number one and number seven, I see that there is a big, big difference with the amplitude. So the horizontal movement north, south seems to be very big for the station number seven and very low for the station number one. If I want to put only these two seismograms, I can also display only some components like north, south. So display in the settings window, I can display only north component. And so I can compare two components and I can see that there is a big difference. So the differences are mainly with the amplitude. But I can see also here that it seems that the ground motion, the vibration according to the waves, the duration is bigger. So it seems that the ground motion stay more time in station seven that in station one. So this is another aspect of what happens. So in that case, I can see this difference. Okay, so this is one very important element. I think I hope you have seen this correctly. Of course, I can do the same with over so I come back to to the seismic center. And I can also choose. So I do the same. And I can see if in the database. There is all over earthquakes. So I can. I can see. I have seen in 2021, the Greece earthquake, but I can see also that I have one in the legally so it is in Italy to close to the border with France in September 2019. And there is the key words of this database, there is site effect. So I can. Well, I can experiment these two. So it's not the case of study of home that is also site effects. So I display with tectoblob once more time, I'm going to go a little faster. So my example here, I have an earthquake, the red point. I have free station. If I want to improve the map, I have to ask a satellite image. Okay. So you have Mena station very close to Monaco, Monaco city. And after you have two other station Niles and Glenn, this is station in the city of Nice. On the right side, I have only the Z component for Mena for Glenn and for Niles. So I have, if I want to compare, of course, if I can display seismogram the origin time. The seismic waves arrived in Mena first and after in Glenn and Niles. But what I want to see is to put in the same scale, and I see exactly the same that before. I have a very, very big difference between Niles and Glenn. These two stations are very, very close. So at the same distance to the epicenter, but the amplitude, the duration and the frequency of the data are quite different. So in Niles, I can see a long duration. I can see a big amplitude and I can see a very low frequency in the waves. And if I compare with Glenn, it's completely different. So that's mean as we have seen in Rome, we have a big difference between two stations. These two stations here in Nice are, and maybe it's what I want to see. Niles, where there is a big amplitude, the low frequency of a big duration is completely in the lower part of the city. There is a very flat zone and Glenn is on the rock, on the rock on the limestone, limestone on the Alps. And so Glenn is not on the same geological place than Niles. Okay, so now I'm going to, coming back to my slide, as I said before, so we were, oops, okay, so we were here. And we have compared the data in Roma recording from Greek in two stages. Oh, no, sorry. I don't know what happened. Okay. Can you see the slide now? Yes? No? Yes, yes. Okay, so this slide is, they are not the website now. So it is a copy of a screen. We have seen this. So we have seen that the two stations has not the same amplitude. And if I come back to the geologic map, I see that there is a big difference between the two stations, the number one and the number seven. The number one is on this green part of the geologic map. And this is volcanic deposit and sandstone deposit. So very concrete rock. And the number seven is in the Aluvian deposit on the Tiber River in this blue part of the geologic map. So the geologic bedrock where the sensor are located are not the same. So if you and if you see you and if you compare the seismogram, you see that the amplitude, the frequency, the duration is not the same. And we have one explanation is that the fact, the geological aspect of outcrop can be important. And the motion, the ground motion is not the same on deposit, alluvial deposits from the river or directly on the concrete rock. So it was the same for for the French Italian border. We have seen that the plan is on the rock limestone and nuts were an alluvial deposit with a site. It is what we call site effect. And when I am teacher, usually I explain to the student that if I am far from the epicenter or close to the epicenter, the intensity is not the same. It is right. So you can tell this to the student. But in fact, you have also to consider that you speak with a homogeneous crest, but if you have not the same rock along in your area, you can be surprised with the effect of the of the waves, according to the geological aspect. So the intensity decrease with the distance if the if the crest is homogeneous, but in fact is not the same always. So this is the Mediterranean earthquake in the in the area of Nice. So on the left part, it is what we call, we can imagine if there is an earthquake, the earthquake if this earthquake occur. I will have the strong effect in the city of Nice, and then an effect less and less and less with concentric circle. But when I look at what really happened. So when we have testimony of people or we have testimony because we have done observation on the field, we see and you can see with me on the right map, the red curve show the place where the ground motion was bigger. And so you can see that well, there is a bigger effect in very close to the epicenter but you have also some place where the ground motion was strong enough to have testimony from people or some destruction. And you can see that we have not this concentric aspect and we have more some place seems to fill the waves more than other places. So that's mean that maybe we have to go to the geological map or to be urbanization and to see what happens in this area. Another example is that one. This is an earthquake in the Alps and you see that we have no concentric aspect and you have a very complex macro seismic map. That's mean that the effect of the earthquake and the testimony are quite different between one area to another one. This is what we call size effect. Another one that I go through. So this is what happened seismic waves propagation. Well, the waves decrease, decrease, decrease with a distance, but when the waves for some places for some site, we have amplification of the ground motion. And it is what we have to to understand. Okay, so data we have, we explore data and we have seen what what happened with the data, the data show that we have not the same record in two places, according of a geologic place where the sensor are located. So when you are when we are in a live your deposit. It seems that we have a big amplitude of the waves and when we are in a concrete rock, we have the waves are completely decreased. You can with students, you can make a simple experiment at school to show and to experiment what happens. So you have here the device that the students have made by themselves. So this is a wooden beam, a load out so they have made a little, a little place and they feel this place with you can feel with candle wax, jello, or if you have nothing like this you can use a sound or sound with little water. And so you put these two things so you have a, and you can use a microphone that we call piezoelectric cell, I will explain to you how to put this experiment at school. They put one microphone on the wood and the other microphone on the wax. And now I am, I hope it's working. I am a little video to show you this. Can you see the video. Yes, yes we can. Okay, well it seems quite simple to do this, and it is, and it is. So you need, you need just some, some element to do this, you need a piezo cell. So this is what, what is piezo cell they are microphone you can find this in electronic shop. You need two of them because you have to, to plug the two piezo cell directly with a cable audio cable directly in the computer. You have to link to the line in because you need to signal and to independent signal so you need to microphone and you need to plug this two microphone by in the same, in the same plug that we call line in. And then you will need to use a software that we call audacity audacity is a free software so you can find on the web, the audacity and you can download it. You have just to record data and to look the difference between the two microphone, and you have to signal to independent signal and so you can compare what happens on the microphone number one and the microphone number two. So you need also to prepare your, your wood and your wax or jello or sound to do the site effect. So we have seen that the amplitude is not the same. So it's okay. And now you can also imagine if the amplitude is not the same. If the, the frequency is not the same, if the duration is not the same, which is the effect on the building. So for the building you can do simple or more complex experiment to show this kind of things. So on this video, you can see a model and experiment with a building made a very simple this building are on the on the plate. And this plate will move will be moved by by sound by a speaker, but you can also move this plate by yourself with your hand. And the idea is to move the plate and this table vibrating table to move with beginning with a low frequency, increasing the frequency or decreasing the frequency and look at the building what happens. So let's go for the video. We begin with low frequency. And you can see that it's not always which is a vibrating because of the frequency and when we're in a high frequency you see the small building moving and then we decrease the frequency and now we can see that we go again and we see the vibration of the higher building. So we can see that the frequency of the of a ground motion can have an effect on the building. If this kind of experiment is too difficult for you to to make at school you can also use a just a piece of wood and you make this free building free stem you put a mass on on each stem and you make a vibration of the of the wood and you will see when you shake the wood quickly it will be the smaller building which move and if you shake the plate slowly it will be the the highest building. So in fact it's it's what we call the resonance frequency and there is some there is from a mathematical formula to to see if we know the resonance frequency on the ground motion and we can expect and we can imagine which building will be moved more than the other one. So this is what we can you you cannot do easily. So it's the reason why I show you by slide in the research center we we make this kind of diagram. This diagram show well it's not complex but it's difficult to draw by yourself. So the idea is to show you the frequency it's in hertz okay and the other axis is the relation between the amplitude the horizontal the amplitude of the horizontal movement according with vertical movement. So if I look at the station number one I have always the same curve h h v and and a frequency but if I look at the station number seven I see that there is something strange if I compare with number one I have a very high peak this high peak is at 0.9 hertz so at this frequency it seems that the horizontal movement is very big if I compare with vertical movement. So that's mean that at 0.9 with 0.9 hertz the ground motion the horizontal ground motion will be very high and so there is the reason frequency of the building is if I make the calculation with this on the station number seven I see that it's not 11 stairs but 11 floors sorry I make a mistake. So 11 floors something like 27 28 meters so 28 meters for the station seven so that means that in Rome at the place where there is the station seven everything with 28 30 meters high can be shaked and nicely shaked by the earthquake. Back to our column the Marko-Reyland Triumph column is something like 30 meters so we are just very close to the to the for the height of the column which is the resonance frequency. Back again for the Roman column you have the geological map you have a place now where the column are of course I give you this information only now because it can be interesting to do this now so you can see that the column the Triumph column is on some volcanic rocks so very concrete element even if this column is very close to Marko-Orel column and in fact the Marko-Orel column is a sandy alluvial deposit and so that means that the movement will be higher and it's for that reason that we have seen this shift in the back relief so the Marko-Orel column was shaked enough to move a little this very big block of marble and now we have this shift that we can see it is well an archeological proxy for the earthquake of course I cannot calculate the magnitude of this earthquake but I can see that this column was shaked by the earthquakes and Triumph column didn't move a lot because of an of course the earthquake which has done this is one of the strong earthquake of the second century and of course now Rome has to consider this Rome city has to consider this because every day new building are new building are necessary to welcome the population and so that's mean that now in the area of Rome there is a urban area which increased and increased year by year so that's mean that people and authority has to consider this aspect of seismic effect to see where and which kind of building we have to to build along the Tiber river along the Tiber valley and where it's more appropriate to to welcome the population so it can be important to to consider the site effect it can be it is important in every every big city if I if I have a and I have time enough to to speak about Mexico City it's a mega city as you know in South America and a lot of earthquake occurred there also and the city is very vulnerable to the earthquakes for example in 1985 there was a very big very strong earthquake magnitude 8.2 so very strong and it destroyed the city you have some picture of this destruction you see a lot of people who try to to search other people to to help to to do something and you can see also some building completely collapse and some other one not collapse collapse and they are very close together so if I consider this earthquake the earthquake occurred usually on the on the Pacific subduction zone so for example in that example you have the epicenter was on the coast of of the Mexico and so the waves are going to travel everywhere and especially in direction of the Mexico City and you have in this picture you have the seismogram and you see that at the beginning the amplitude and the frequency the amplitude is very high and the frequency very short and then when we go to Mexico we which is at 400 km so far away the the seismogram show amplitude decreasing and decreasing and decreasing but if you compare UNAM just on the volcanic bedrock and the SCT which is another sensor directly on the sedimentary deposit you can see a big difference between the two ones so of course if I compare UNAM and SCT the two seismogram are completely different of course inside the Mexico City the ground motion was completely different that in the border and all the and the building in Mexico City were completely checked by a very high amplitude very low frequency so we have to calculate the reasons to see which building where collapse or not and the duration also so that means that the duration is big so the building it checked a long time and so it's more vulnerable if it shakes a long time and if we go back to the if we go back to the picture and if we go back to the experiment you see that you can explain why some building were not collapsed and the other one yes because there was a resonance frequency a particular one and all the building with a specific hate where collapse and not the other one and in that case in Mexico it was not the highest it was not the lowest but it was in the middle all the building in the middle hate where collapse because of the operation and if we go back to the geology we have to we have to come back 700 years ago and we see and we understand that Mexico City like Venice in Italy was built on the lake and on the land where there is a lake so that's mean that all this area where the Mexico City is is directly built on the sedimentary deposit of this all the lake and so of course if you look at the seismic zoning and so that's mean that my color we we try to evaluate the risk and the maximum risk you see that we have red zone so the red zone means that the risk is maximum so that's mean that an earthquake occurred the ground the ground motion will be very high and with a very specific frequency and so this place can be difficult and especially vulnerable and you have zona in grey or in yellow where it was not the lake before and so of course the situation is a little better for the for the building so you can understand the seismic effect by the properties of the waves and the geological aspect so you make geophysics and geology at the same time it's necessary to understand things so you can make geophysics geology and also engineering and you have all the the package to understand the vulnerability of the city because of earthquakes and you can understand also which which kind this kind of seismic alert in Mexico so Mexico understood that the earthquake occurred on the coast where waves will travel until Mexico and then in Mexico we will have a seismic effect so if we can know before the arrival of the seismic waves that the seismic waves are arriving and so they have a system to record the epicenter with seismometer located on the coast so the seismometer record the waves and after with a signal which go faster than the seismic waves of course we make an alarm in the Mexico to alert the well the authority that big seismic waves arrived in Mexico City and so we can maybe close as stop traffic of the trains or things like that just to reduce the vulnerability of the earthquake so to resume it to conclude this so this is what you can keep with your students as a synthetic diagram so if we consider only the S waves and it is interesting to consider the S wave because the S wave is the horizontal they when they arrived on the surface of the ground they make they produce horizontal movement this is the S waves and so we have a reference station the reference station is always in a concrete rock and bedrock so we have a seismogram for the reference station in black in my in my figure and then you have some increase of the amplitude frequency decrease duration increase this is site effect and you can have size effect in several situations for example when you have a large thickness of sediments in green on the right part of the of a diagram so it's the case of the major of the big city in the world because when you the city built all the houses and the population join this place very flat with a lot of sediments so if you are living in a seismic area you will have a big seismic event it can be a sedimentary basin so it is quite the same phenomenon than the launch of the large thickness of sediments and you have also topographic topography site effect so the waves stay in the mountains and and make the mountains move shaking a long time and making some increase increase of the amplitude this is don't this is all the this seismic aspect so you have seen that in Roma in the old movement we can find some proxy of this seismic site effect and you can maybe in your area when where you live when you teach maybe you will have some example like that one which will illustrate for you for your students this very important aspect of the seismology and for the citizen seismology so the site effect the importance of the geology and the and the buildings and it's very important because in the future we hope that this element will be important to build new cities for the future. Thank you very much and if you have some questions please do not hesitate. Should we read Teresita are you in charge of the chat maybe I will go into the chat and see the questions and I don't okay I will do yeah I can see I can see the chat Stephen so I can thank you Teresita to give you some link for that city and well for Tectoblob and Tectoblob somebody I think it's Susanna Brandao. The question is how can we determine the amplitude with Tectoblob 3D so you you cannot actually we have no implemented a tool to to calculate the amplitude so we can we can do this but you have on your left side you have you have some scale so you can approximately calculate the amplitude but in the best way we will have access to to to look at the amplitude but it's difficult sometimes to to calculate the amplitude because we are we have to know exactly the the specificity of the technical the technical aspect of the sensor and so sometimes you can calculate the amplitude so we can not publish the data because we don't know exactly the scale of the seismograph and we have another question I didn't write the name but I read the question how is possible to find similar data from other earthquake from other recording center so you can find data on a on a lot of seismic website researcher website most of them are research website and this is the problem when when you are teacher because the researcher center publish data but for researcher purpose not not very often for education purpose so this is why I show you edumade of course I am in the edumate team so I know this but you can try to keep in touch with a researcher center close to your school and to ask to to ask to to seismology data and if they provide you data in in the right format for tectoglob you will be able to use this specific data with tectoglob to you need only to ask to the scientist a data in SAC SAC format and when the tectoglob see this SAC format data is able to open the data like I have done with you or if you have a data you can contact us or contact me and we will see if we can help you to use this data with tectoglob but the first step is to go and to to try to to catch seismology close to your area to ask in some data to illustrate this aspect or other things but on edumate data you can find already a lot of data with Greek earthquake, Portuguese earthquake, Italian earthquake and relink with volcano and earthquake so you can find already a lot of examples but the best example is the example that you will find a very close of your city because he will speak more for your student. Maybe one more question and then we will take our coffee break. Teresita. I found no more question on the chat. Okay so I can I say that the best way if you have more questions later so contact me I can write a mail to contact me and so that means that you will you will ask me questions if you want more. Okay Stephen. Thanks for your attention. Okay we will take a break until 3.45 and we will reconvene hearing about Machu Pichu. Okay so go get your tea, your coffee, cappuccino and we will see you back at 3.45. So welcome back from the break. We are now going to the first of two talks for this afternoon and this morning in Virginia so just I didn't introduce my co-host for this session is Teresita Gravina and I am Stephen Mako. I am a professor at the University of Virginia in the eastern United States. I teach things like oceanography and do you have a statement Teresita or should we go to Carlo? I guess we will go to Carlo. So go ahead everybody online I see I can't hear but I think the volume is up. Anyway so the rest of this afternoon's session will start off with Carlo Lodge and you heard from him yesterday on Monday and so I don't think he needs further introduction but he will be talking about Machu Pichu. So Carlo take it away. Okay I am on. Okay so Machu Pichu lost city over in because the title of his stock is not mine actually I borrowed from a book written by Ivan Bingen the American explorer who made Machu Pichu known to the world. It's discovery of Machu Pichu dates to the July 24, 1911. And this plate here is the entrance for Machu Pichu put for the 50th anniversary of the discovery. I like the date 24 of July because it just happens to be my birthday but I don't think I don't think Bingen thought of it I was not I was actually minus 28 years old at the time. So let me say a few words about Ivan Bingen he was first of all when he discovered Machu Pichu he was convinced he was looking for another town called known as Wilcomamba which is the capital city of Incas where Incas had escaped after the Spanish conquistadors came in. And Ivan Bingen thought that Machu Pichu and Wilcomamba were the same and only one but he was wrong and but this was proved wrong after his death. He was native of Hawaii he was educated in Yale University in the state on the east coast and he later talked about the university he had a colorful career including being an Air Force troop commander in France during World War I he was elected senator and he wrote several books about South America civilization he died in 1956 and is buried in the Arlington National Cemetery in I don't remember it was July or June 2021 100 years after his recovery I happened to be in Lima for my research work and working around Lima I discovered a let's say an expedition of photographs and documents open air in the street and no copyright and because I had my camera with me I tried to make a short video of this and this short video is interesting because it shows how Machu Pichu was when Ivan Bingen discovered it and I would like to show it to you here is where he left from Cusco and he passed through and before and here is in front of his tent in Machu Pichu he was very tall they stood very impressed with people this is how he had to pass the Urubamba Rio Urubamba in the valley below Machu Pichu and this is the view of Machu Pichu we got in the back wine Pichu Machu Pichu means the old mountain wine Pichu is the young mountain and this is actually exactly the year he discovered Machu Pichu was covered with vegetation this is later on when most of please large part of vegetation has been taken away this is the principal temple we'll see more of this later on in my talk and this is the man who we were chatting and taking the vegetation out then there is a section of the mountain and this is where Machu Pichu was discovered by the vegetation out then there is a sacred rock with somebody standing in front of it and this is the view which what you have to look at or incidentally this is the only round temple with a trapezoidal window and you have to watch how nicely the different construction stay together there is no trace of cement between them and the stair for instance is there the vegetation is not altered this fantastic look and we can we use it today so going up when we come back to the below we will see this place here it's a fountain also admire this big ball how nicely it has survived 500 years and here is a small boy with he was crushing corn or frozen potatoes here is a sentient Carrasco who the governor of Cusco had asked to follow Iron Bing and both was interpreted as an escort and finally in this small video and we get to the three windows temple here covered with vegetation and this man proudly standing over there because he had cleaned this part now the next site is taken from the top of Waianae Pichu and looking at this you can see that there are about 700 meters on the right side also 700 meters to be valid so one question which one may reasonably ask is how why and how did Mainkas build Machu Picchu in such a remote and inaccessible place so this isolated location is most probably linked to the religious status of Machu Picchu whose construction was sorted by the Inca ruler Patsha Kuti about 500 years ago but there are other reasons in particular that are geological reasons which were a determining factor for the precise choice of a location of Machu Picchu so let's take a look at the geology of Machu Picchu here is a map of South America taken from an article by Roper Shetal published in 2006 in tectonics I am together with a student of mine I am a co-author of this paper which relates to this region here you can see the western Correa the eastern Correa here and in between the two there is what is called the Abankai deflection a deflection which happened later after the eastern western Correa were built and we were working there on polymonetic studies to see when and how much of rotation had occurred so you know why I went to see Machu Picchu I worked in Peru for about one or two months a year for six years and I visited Machu Picchu six times and every time it was a fantastic view so let's look a little bit closer to this here we have a view of a graven sorry I forgot to tell you that the two folds here were this is the Machu Picchu fold and I should have shown a little bit more the map before because everything is stuck I don't know what happens you know okay so let's go back to this sorry I skipped this there are two major folds this is the city of Machu Picchu Machu Picchu fold and the Waini Picchu fold both are normal folds so that the center part has has gone down here is please notice this there is a primary spring which is very important as I will tell you later and this is the block of a graven on which the city of Machu Picchu was built as early as 1987 a researcher from Peru working at Berkeley did a study remote sensing study of the Machu Picchu region and the map down fracture and folds this is the figure 11 of his publication and so he could see that some of his folds were parallel to the Machu Picchu or Waini Picchu folds but there is a second family almost at the right angle so that they made an X X right at the place where Machu Picchu was built this was also confirmed later on by a local study between Agua Calliente in Ubelli and Machu Picchu by Victor Carlotta whom you will see Victor is a geologist from IGP Institute of Geophysics at Peru and finally recently in 2019 from the Federal University of Rio Grande do Sul did a very extensive study extending the geographical geographical zone to 100 maybe 150 kilometers and he said he proposed a solution which is now accepted everywhere but the intensive network of folds of different orientation caused intensive fracture action of the granitic butylite and so providing blocks of let's say manageable size at the surface in what it's called natural force so here it's another view from the wine in Picchu and you can see here the place where the blocks are still there in geological terms it's called the Egalitic Curse which is a closed view of the blocks and which are on top of another zone again here we have an idea of how we think as block the stones to the sides we really want they pushed some wooden pieces wet and so when we froze they broke the rock down and break us where master son worked so they carved the stones to perfect side perfect shape in a way in a wall or any construction the blocks would be fit so tightly on one another but it is impossible to to put even a piece of sheet of paper I tried with a ticket from the Paris metro line and did not succeed so this is an example of a wall in Machu Picchu the the different blocks fit together in a perfect way some sort of jigsaw pattern and when when the earthquake occurs the local sign is that they the stones dance and after the earthquake they fall back to the original position so this is some sort of anti seismic structure and technique which is called ashlar or dry stone another example of a wall at Lentimbo you can see how perfectly the different stones fit together the most known is the 12 corners rock at Cusco here we we can count with 12 corners and here on top the three windows temple which you have already seen is also an example of a nicely tightly the different blocks the different rocks were put together they could have had a flat surface here but they had an additional corner here so that the building was much more stable so this is how the incas took advantage of a local structural geology to choose the locality for Machu Picchu so can we think that the incas had the knowledge of a structural geology of a Machu Picchu area certainly most certainly not in the modern meaning of the term the term structural geology but they were certainly aware of faults linguists have identified a wall like here in their original language which means fracture and the incas most probably knew that the faults are linked to water seeps and this is why most archaeologists believe that they located a fractured zone by falling these seeps from down in the valley up to Machu Picchu location and yeah we get to a second geological actually hydrological factor or an essential reason for reconstruction Machu Picchu water Machu Picchu hosted between 600 and 1000 years so of course they needed drinking water lots of water for their home use and here is the moment where we have to consider the distance of the spring which I mentioned in the Machu Picchu Machu Picchu mountain and of course this spring single spring was announced by a well very impressively engineered collection system this comprises a series of under of long canals and an impressive sequence of 16 stone-lined fountains and this was sufficient for drinking and for ceremonial and domestic waters cascading through the sea yet the ink is said to so they chose this place because of the software geology allowed them to have blocks of manageable side and because the water the spring allowed them to have enough water for domestic and ceremonial use but they had to face they had to face a seasonal precipitation which would have been very can be today also very impressive sometimes 150 to 150 cm per year and they would come in a certain way so if nothing had been done the construction of Machu Picchu would have been washed down but the ink is built they had to built an efficient drainage system and sorry so that two thirds of the city are underground and the first step of course was the construction of stabilizing terrace these terrace are built in such a way first they are very strong and well attached wall was built then they they first put a start of boulders then gravel and soil fertile soil which which is the term which is the soil in full of organic material and this structure there had made the water move very slowly so with minimum erosion and allowed the the city to be there so it is now time to show the second video on my presentation here it is this is the Inka trail coming to Machu Picchu from Kuska still you can use it it's a four maybe five days walk from Kuska and it arrives here in the upper part of Machu Picchu and you can see so this is the main entrance Machu Picchu you can see here the cows on the northern side this is the bridge which now exists on Urbamba and this is called the Bingham Highway here you can see the Machu Picchu fault and luckily enough you don't have to walk up all the way 700 feet buses do it for you it is a long way anyhow so we arrive at the point where the Bingham Highway joins the the Inka trail and then we move around in town this is the view from the Waena Picchu as there is some people think that Machu Picchu looks like a condor with a head here I I don't know this is the classical view of Machu Picchu with the Waena Picchu with our construction up to here and this is the place from where I took the video we have just seen and we can visit again the town there are no roof because this we are made of vegetables and then washed away this is one of the fountains as I said there are 16 of them distributed all over the city of Machu Picchu here is the second one I will not show all of them but at least four or five of them to show that the water is still coming and very clear it is drinkable water actually I drank years ago and I am still alive so it means that it is a good quality water very clear and this is based into a granitic block which the ink has carved and I don't know how we could do this again this you have seen in the first one of the first slides of the first movie sorry here the water is pouring through at another good rate it has been so for the last 500 years despite the town the city was abandoned and as soon as the vegetation is taken out the fountains started again here is the view of Victor Carlotta pointing to the cows explaining how this was used for reconstruction of Machu Picchu the here you can see the principal's temple we have already seen and the rest of the town and now it is this is the place where Rienkas had their agriculture plantation in the view of the cows of a different block which evidently were not used this month and we move again to the principal's temple which Victor indicates here it is and part of it has been damaged not because the wall was not strong enough but because the soil was not strong enough on the right side as Victor explained to us these huge stones were not well carved in this way because that allowed transportation more easily it is not because Rienkas did not succeed in carving so it is a little bit too long now we go on the back of this wall here and this is the top of Machu Picchu on the back you can see that despite the ground was not strong here is a group of people who are the students teachers attending the attending the gift 200 2000 gift workshop in Kursko again we see the temple of the sun with a trepidate window and finally we get to the top of Machu Picchu and this is the Inti Watana rock the one you have seen already in the first video Sergeant Karazko was very close to it now we have a closer view the final slide you can see that this rock is strange you can see that there is some shade projected by the rock itself but there are two particular days the summer and the winter start this where the rock does not project any shadow so how is this possible because Machu Picchu is not much greater it is 30 degrees 13 degrees south so this is only possible if the entire Inti Watana rock is cut with an angle of 13 degrees with respect of the horizontal and also if you project this direction here you get to a point where the sun rides if you project the other side the other way you get to a point where the sun sets during the two equinox so the Incas were not business of city they were also astronomers now this is the end of my talk if you wish to know some more I encourage you to read the original book by Ayran Bingo it is a Sentinel edition which is available today for a few euros or less I yield which means thank you this is the end of my talk Steve, it's up to you thank you so much Carlo I ask Steve to activate his video and microphone thank you so much for your very interesting talk I had a look of the chat but it seems that there are no question but if someone is interested in learning something more you can write your question on the chat Carlo will be very happy to answer I have one question Carlo it's very easy can you repeat please how do you say the title of the book can I say what the title of the book it's called Floss City of the Incas okay Ayran Bingo okay, perfect thank you so much everyone in the chat is very happy about the presentation they have no question but they are very happy about the presentation I think that Steve has some problems because I say that is no more in the call so we wait a little bit to see what happened and okay there is Loss City of the Incas okay and I really think that this is a fantastic fantastic book romantic and abstract exploration I am in love with Machu Picchu as you can imagine I wish I could go there again okay do you think it's also good for the students to be read or it's too complicated book no no no it's very easy to read I could have read it when I was 14 it's a kind of a book I really enjoyed very easy to read no problem at all of course they did not know about the structural geology problem we described it's exploration and it's a fight to get funds to clean it up from the vegetation and to no it's really a good book okay perfect thank you so much for this interesting suggestion I cannot found Steven in the chat but I will try to go ahead with our next speaker please sorry for my bad pronunciation Yannick Davos yes I pronounce you quite well your name yes you did great you have the right as co-organizer so you can share your screen is this working okay perfect so I'm going to present you I'm sorry it was like a surprise for me to have to present and you're going to talk about a very interesting topic urban geology in Belgium okay let's see please go Yannick thank you so much thank you well first of all I would like to thank you organizers for giving me this opportunity to talk about one of my favorite topics which is the legacy of urban soils and sediments now I'm a geoarcheologist and that basically means that I apply methods and principles from the earth sciences and from archaeology and this in order to study past interactions of humans and their environment now this presentation I would like to show the potential of urban soils and sediments to understand past urban development and also how we can come to a better understanding of how people were actually interacting with the environment in urban areas in the past now yeah it's working soils and sediments are an essential part of towns and they typically remain hidden from view and they basically only surface during road construction or demolition works and that also implies that they do not get the attention they deserve nevertheless urban soils have many different functions and for now I would like to focus on one specific function and that is the memory of urban soils because for me as a geoarcheologist the soils and sediments themselves are the object of my study now why are these urban soils and sediments so important for archaeologists well there are several reasons the first one is that all the archaeological objects that we find during an excavation well they are surrounded and protected by the urban soil and I give you some examples here this is an excavation of the ancient harbor of Brussels in late medieval times and what we see here are all these wooden posts that are still nicely preserved within the sediments that have been deposited by the local river which was a center river and another picture here is also from the historical center of Brussels and this time we are in the neighborhood where in medieval times all the butchers were situated together with other artisanal activities and what we see here are basically hundreds if not thousands of mandibles straws basically of animals mostly cow and sheep that were broken in two to extract the oil and then were deposited within the soil and preserved until we excavated it a few years ago from the same archaeological site we have here a nice soil profile and where we see basically all these fragments of brick again nicely preserved within the urban soil so we can say that the urban soil serves one way or another as a kind of container that preserves the objects inside but it's not always true we have to be careful about it for instance these wooden posts were only preserved because they were preserved in permanent wet conditions so that biological activity did not get the opportunity to decompose the wood but in many sites all the wooden or even organic plant remains they are quickly decomposed and they are no longer part of the story that can be found during an excavation and the same goes also for these bone fragments they were nicely preserved because we were dealing with a calcareous soil a soil in which the bone material could be preserved but many soils are very acid and that implies that the bone material will decompose very quickly and so the bone remains will disappear so that's something that we should always be careful about now a second reason is that soils and sediments can also directly witness of ancient activities and I'll show you an example from this same site and now we're not talking about the objects but we are talking about these grey traces that you can see here and these are what we call implement marks these are marks that have been made by spades so people have been spitting the earth doing agricultural activities and what we see is that even after 700 years because this site dates from about 1300 so even after 700 years we are still able to observe these traces and that also implies that we can identify the activity that was performed there 700 years ago the third point is that soils and sediments can also witness of landscape evolution and I'll show you very quickly here three profiles from the historical centre of Brussels showing different episodes basically where we first have an area that was still covered by forest and then we have this typical profile indicating medieval agriculture and then the most recent part where you really see this urban soil appearing so witness also of landscape evolution and also an important factor is that soils and sediments are also resource and this is not only true for today but also for people in the past people were using sands, sills and clays as construction material here you can see an example of what will endure construction but also for the making of bricks and ceramics so also soils and sediments as a resource now to use the words of one of my centres we can basically compare a soil with a book and I would warmly like to invite you to read together with me a few pages of this book of urban soils now the first step we need to do is to open the book and for that we need to dig and over the last decades I've had the opportunity to study a lot of archaeological sites in the historical centre of Brussels just to orient ourselves a bit so in green we can basically see the surroundings of the first city wall which was built in the 13th century and about 50 years later people have been building a second city wall which is indicated in red now all the dots that you can see are excavations where we were able to perform a gearchological study the ones in yellow have been studied the ones in blue is still very much work in progress but you can see it's quite a dense grid giving us quite some detailed information as we will see later on now if we are talking about urban archaeology well sometimes we are facing enormous and spectacular excavations this is an excavation of a few years ago in historical centre of Brussels where an ancient parking lot was demolished for the construction of a new administrative building and so you can see the surface that was excavated was enormous and what we found there were the remains of the ancient harbour of Brussels in medieval times it was quite a spectacular excavation but not all the excavations in historical centre are that spectacular these are what I would call the more typical ones and these are all these small trenches sometimes only a few square metres large quite often very deep but all these small trenches together are providing us with tremendous amount of information so it's not because they are small that they are not interesting now we are working quite a lot in Brussels but also had the opportunity to study other towns in Belgium especially in Flanders quite some excavations in the historical centre of Ghent and Antwerp and also had the opportunity to go to Lige to the oldest town in Belgium which is Tongeren dating already from Roman times and also Vilfer de Aust, Aldermen and Ibra so quite a lot of different towns where I had the opportunity to have a look at the urban soil now and the first thing we see when we open this urban soil is complexity we see a tremendous amount of layers one cutting through the other it's not really a surprise because we are facing several generations of occupation one after the other each time creating new deposits demolishing part of the previously existing stratigraphy so we end up with something which is very complex and a colleague of mine tends to compare urban stratigraphy with the severest type of that archaeologists can face and it's maybe not so far from the truth and within this complexity there are a few types of layers which are extremely difficult to interpret based on field data the first type are what we call dark earth and these are these thick deposits that do not really show any internal stratigraphy so they are very thick, very homogeneous and they cover wide surfaces and they are really very difficult to interpret based on field data and the other type is quite the opposite that are what we call these layers are only a few millimeters thick and that also makes it quite difficult to distinguish them and even more difficult to interpret them based on field data alone and that's basically where the archaeologists come into play and I will now take you to the historical centre of Antwerp which is situated in the molten part of Belgium here so this is the historical centre of Antwerp this was an excavation that took place in 2009 and so there were quite some spectacular discoveries so we had a nice preservation of all types of organic material there was a discovery of medieval trackway, there was the earth and ramparts of the first city of the town so there were quite some spectacular findings but the archaeologists also discovered this kind of succession of very thin layers, one on top of the other about 100 different layers were discovered like that and well if we have a look at the dating of these layers then we see that they only cover a period of about 100 years so in quite short time span they have been developed and of course the question was what are we facing here and how can we study this and that's where micro morphology comes into place and micro morphology is basically the study of soils and sediments in what we call their undisturbed state and at the microscopic level. Now what do we mean by saying in an undisturbed state well that means that we are taking samples specific block samples where we really take a block of soil out of a profile we put an orientation so that we know which part of which part is down and then we impregnate this with resin, we cut off a very thin slice of about 0.02 mm thick and that's something that we can then study under a microscope. What's interesting about it is that we can observe all the components in their original position so we can for instance see the pores you can see different types of pores here you can see the minerals of which the sediments are composed you can see all kinds of inclusions and here we have fragments of top we have sort of charcoal fragments here but we can also identify ancient excrements this is probably an excrement of a human being yes and then we also sometimes even see parasite eggs so there are quite a lot of things that we can observe so the interesting thing about micro morphology is that we can observe everything in its original position so there's no concentration on different elements everything is still there and basically it's the continuation of what we already observe in the fields but at a different scale this time at the microscopic scale and this is very interesting for these very tiny layers because now we can study them in detail and just to show you an example of one of these layers that we've been studying so this lowest part here we took a block sample and well to give you an idea it's about 8 centimeters high and about 4 or 5 centimeters large and what you can see here is that you have two clearly different deposits the lowest part and the upper part they're quite easily distinguishable and they also testify of different kind of activities the lowest one is basically a floor a floor of a house nope not there yet well the upper part is basically the remains of a stable so we see all the fodder that has been accumulating there all the organic plant remains you can still see they're nicely horizontally oriented so basically by looking at this what we call thin section we can already distinguish two different layers and not just two different layers we can also see a succession of activities first we have this house floor within a domestic floor and then we have later on a stable if we go to the upper part of the sequence we can again see different layers appearing and here we have at the lowest part again a floor from domestic house and for the other part we see an accumulation of ashes this is made of pure ash so basically by performing this microbiological study we can identify the succession of events and we can also see how this one single location is modified over time and what people have been actually doing at this location so this is quite an interesting sequence that we were able to identify there now if we have look at urban dark earth then it's of course a totally different story that we are going to tell now coming back to what are these urban dark earths well it's basically an expression that is used by archaeologists to indicate the fact that they are facing these homogenous thick dark colored layers that are often which in human materials and cover large surfaces and here you can see a nice example of this well they are occurring all over Europe and you can see an example from Aquilea in Italy there's another example here from London another example from Strasbourg and just to give you an idea all the countries in blue are basically countries where these dark earths have been studied in quite some detail it's really European problematic and well if we look at it in detail then of course the first question we ask ourselves is what are we looking at it looks grayish you don't see any layering in it what does it represent is this just a leveling layer is there something going on we have no clue and well in the past the idea was these layers were considered to be of no archaeological interests so the idea was we try to get rid of them as quickly as possible but of course that also implies that we are destroying part of our heritage without even looking at it so that's maybe not the best idea so in the next step well the archaeologist proposed let's see if this deposits and let's have a look what's inside and we get some very interesting results because now we can in a very detailed way say what are the archaeological remains that are inside of these dark earths so we know something about the contents but we still have no clue on how these dark earths performed nor what are the human activities that are related to these dark earths so for that we need basically a gearchological approach and it already starts in the fields by performing detailed observations and taking the necessary samples then there's of course the step of performing the necessary chemical analysis and of course also micro morphology I've already shown an example of the application of micro morphology for this very thin layers but we can also apply it to dark earth as we will see now now proposed to go now to the town of Audenard to also situate the plunders and then we had discovered this dark earth here you see it's about 30 cm thick and yeah the question was what is this, how can we study it and well we took a series of block samples you see already a block that has been taken there but we also took a block down here and here you can see the thin section that we made out of that block and well while in the field you can't see any stratigraphy or any layers if you look at this thin section which is again 8 cm high and 6 cm wide you can immediately see a dozen of different layers and that's basically part of the strength of micro morphology we can make the invisible visible and well we performed quite some studies on this dark earth influence in Brussels and it allowed us basically to come to a better understanding of how they formed and what we basically see is that it all starts with parent material on which different factors are intervening and then we are thinking about environmental factors such as climate topography non-cultural processes and then we are talking about biotubation meaning earthworm activity ants, moles which are all digging their galleries but also plants and roots erosion can also be involved sometimes if the soils are bad they are vulnerable to erosion you can also have decomposition of organic material that's inside you can also have other types of soil processes that are involved that are basically what we would call the non-cultural processes so you can also name them as natural processes although part of them are of course caused indirectly by human activities and then there are the direct human alterations or modifications then we are thinking about accumulation think about the adding of domestic waste manure, cess construction, debris industrial, artisanal waste and so on and so further you can also have the mixing of different materials you can also have the removal of the digging away of part of the dark earth and also compaction can be involved and all that is also leading us to the identification of human activities and that's what we basically see on this right part of this image and then you can see some of the activities that we were able to identify so far within this dark earth so you see that it's not just one single activity leading to one dark earth we have for instance keeping of animals on meadow land we also have keeping of animals inside the restricted areas, the stagling we also have crop fields gardens, market activities building activities quarrying burial activities and of course also artisanal activities so quite a lot of different activities that can be involved it's also very important for this model that we developed is that you basically see that this dark earth it's something that forms over time and so I already said it's not necessarily one single activity sometimes it's a succession of different activities different non-cultural process that are involved so it's basically something that goes on and on until the dark earth gets sealed in one way or another and that of course makes it quite complex to study but also very interesting and that brings us to basically the next point by studying these dark earths we can come to reconstruct a site biography so we can basically reconstruct the history of narchological site not just one event but the whole chronological sequence I will show you one practical example again from historical centre of Brussels so here we have the actual royal palace and in this area was situated in the palace of Charles V and next to this palace of Charles V there was this court of Hochstrater of one of noble people from the 16th century and while we excavated part of the ancient gardens a few years ago and we were able basically to find a very thick dark that we studied in quite some detail and we were able basically to reconstruct a long story that goes back until 10th century where we are basically seeing that we are having some postulant that is transformed somewhere in the 13th century into a crop field and this crop field on top of this crop fields people were then building at the end of the 13th century a stable a stable got destroyed, burned down and then people were adding a lot of construction debris mostly construction debris and rubble basically to create a new surface for the garden of this court of Hochstrater in the 16th, 17th century and while today everything has become part of a museum that you can still visit today so that's basically all site biography that we are able to identify now identifying the biography of one side of course quite interesting but of course we had so many different excavations in the centre of Brussels we can tell something more so based on the study of the soils and sediments we can try to reconstruct part of the early history of Brussels and it's quite an interesting theme because for more recent periods we have quite some detailed maps showing us the location of different streets and houses but if we go back before the 16th century these resources do not exist anymore and if we go even further back in time to the early beginnings the town development of Brussels which is traditionally situated somewhere in the 10th century well there are no reliable written sources at all so basically it also implies that historians are now ready for more than one century having these heavy debates basically on how did this town came into being and how did it develop especially because of this scarcity of written sources and that's basically where the study of the urban soil can help us quite a lot so what we were able through was to map activities so we were able to see that in the 10th, 12th century there were quite some locations in the historical centre of Brussels where we see that we are dealing with crop fields we also have a lot of meadows, we have some quarries and even a lime kiln and what's interesting is that we forget about this first and this second city hall because they were not there yet I told you not in the 10th century and the second one even 50 years later but it's just a bit to orient ourselves so this is basically the core area for the urban development and we see that within this core area most of the activities well they are related to rural activities so they are telling us that Brussels in this period is still very rural in character and that was quite a discovery now when we have a look at the 14th, 16th century then we see completely different picture appearing so again by looking at the urban soil we see that now we have a lot of gardening activities going on and what we also see that in all the sites basically we studied for this period we see that construction activities are very much present likewise metallurgical activities we also see the appearance of market places so we have very much let's say a more urban environment in this period maybe that's really something that is popping up in this period and what we also see is the complete disappearance of these crop fields within this core area when the historical center developed so that's one thing that we can do through the study of the urban soil but we can also say something about waste management and ancient pollution and that is basically a huge problem according to historical sources now a lot of complaints about people throwing their garbage through the windows animals freely wandering throughout the city but it's of course very difficult to measure this and that's basically again where soil science can be of very much importance and so how can we now study ancient soil pollution how can we quantify this can we get an idea about how important this pollution was and that's something that we should be very careful about because if we are going to perform chemical analysis and measuring the presence of different elements we have to be very careful because if you are performing chemical analysis you are basically measuring the actual concentration of different elements and not necessarily the concentration within the 13th century or the 15th century, 17th century so it's something that we should be very much aware about and for that we need to avoid a series of pitfalls it's very important to know at one point what is the background noise what is the concentration of the different elements that are already present in a natural state without human interference also perform what we call a taffonomical study we need to know what happened after the occupation of the site to know is there any recent pollution interfering so these are really very important points that need to be treated first, but if you do that then you can come to some reliable results so we got quite some interesting data about heavy metal pollution in different time periods so first again have a look at this map of Brussels in the 10th 13th century AD and the first thing that we see here is that there is basically no pollution at all we only have very slightly elevated concentrations of copper and nickel and for that it's even nowhere the case and we were able basically to rely these slightly elevated concentrations to the agricultural activities and especially to the manuring of the soil in this period now if we have a look at the 14th 16th century AD then we see a different picture now we see some more elevated concentrations it's also a bit changing according to the site we were excavating and it also goes for the different elements now again we were able to trace back the origins of the pollution thanks to this combination of the chemical analysis with the detailed micromorphological study that we did so we combined both and that helped us to identify the soils among the soils that were identified for this pollution there is of course metallurgical activities no surprise there but also horticultural activities building activities and also burial activities these seems to be the main sources for pollution in this 14th 16th century AD now if we are going to have a look at the concentration or the elevation of this pollution then we see that only in one single case the threshold values are reached that means that in only one case there is potential harmful situation for the pollution so that means that in pre-industrial times heavy metal pollution was still very limited in this case for Brussels and then while as a last point I would like to tell something a bit different scale because we've been looking now at a very detailed scale a microscope almost a microscopic scale but we can also tell something about landscape through the study of these soils and sediments in Brussels and for that I would like to present three more sites first one, two in taxi, Rüde Erskolt and Rüde Boateu let's talk with the site of Rüde Erskolt what we discovered there that was basically a very nice stratigraphy showing us the center river so the local river in glacial times what we see there is that there is no fixed bedding yet so we have what we call a braided river where you have all these different channels one crossing the other so there's no one single big channel so it's all very much moving throughout the landscape so that's the situation in glacial times and then we had another excavation I've already shown you the picture I think, two in taxi it's also situated in historical central Brussels and what's interesting here is that we discovered a branch of the center river that was unknown to us and was dating from Roman times and what we see now is that we are dealing with a meandering river and what's interesting is that we see that these Romans they tried to fix the river in a bedding so they did quite some wooden construction works to try to fix the bedding of the river and so we also performed some additional studies showing us how landscape looked like and it was quite an open landscape that we had in these Roman periods and we see so again going from Roman times we have a nice meander and what we see is that after the abandonment of the site by the Romans and so we are entering the 4th 6th century there then we see that we basically this branch of the river got blocked off from the main rivers there was no water streaming there anymore and we got some kind of marches there a marchy area that rolled up until it completely disappeared from the landscape then the last site I want to show you is the site of Rue des Boiteux in the core center of Brussels and why is this one interesting because here we found a very thick peat deposit you can see it here and so that's something that we tried to sample in quite some detail now why is this peat so interesting well because it's a sequence that covers the last 10,000 years so it starts somewhere 10,000 years ago and it lasts until 13th century and we have almost continuous sequence there so that's very interesting for us why is this peat so interesting well in peat the organic remains so the plant remains tend to preserve very well so they can give us some idea about evolution of the vegetation over the last 10,000 years and what we did is we studied all the different types of remains so we looked at the pollen we looked at the seeds we also looked at the sponge the pilots so these are silified plant remains and also diatoms so quite a lot of different types of remains that we look at in quite some detail and not allow this peat to eccomi sono la vovi stressa dal mastery eccoci niente ho chiamato al cellulare per to capito che era in difficoltà col collegamento quindi eccomi qua eccomi qua so that allowed us basically to reconstruct the environment in quite some detail it starts 11,000 years ago where we have quite an open landscape and then we go from 9,700 to 7,800 years ago where you see these reeds coming into place then we get a more dense marshy areas more forested area and to 3,200 before present and then you see that the landscape is opening again probably due to human influence between 3,000 and thousands before present so that's basically something that we were able to reconstruct and it became also one of the reference sites for the whole region now if we have a look at a more regional scale then we see that we start with an area that is very open a very open landscape with pioneer and precipitation that is arriving then we get the development of very dense forests that get then later on partly cut until we have this open medieval landscape where we have all these crop fields that we were talking about previously so what can we say in conclusions about these urban soils now well I think I managed to demonstrate you that the urban soils have a memory they can help us to detect spatial organization patterns and also how they evolved over time they helped us also to understand parts of this interaction between nature and the urban population think about the changes in the vegetation type where we go from forest into these more agricultural areas and we can also obtain some objective data on the evolution of pollution in times and finally we can also understand part of the changes that are happening with the landscape think about relief but also the river beds that are changing vegetation and so on of course this kind of research is not just the work of one person so I need to thank quite a lot of people who have been contributed to this research over the last 20 years and I would like to thank you for your attention and if there are any questions I'll be very happy to try to answer that. Thank you very much Yannick there is one question from Karolina Damjanowska who wants to know do you use any physical methods to research the age of what you study for example radiocarbon dating for organic remains exactly yes we do so basically the dating of the soils is partly based on the archaeological material that we find because they can sometimes provide us with very detailed datings sometimes up to 20 years and we also are relying on carbon 14 datings but this is sometimes a bit problematic because especially for this medieval period we have sometimes sometimes an uncertainty of about 100-150 years and of course for medieval periods this is quite a large period that we quite a large uncertainty that we have to face with sometimes a bit problematic but we are quite hard working but especially for all these phases of the urban development we do not always have that much archaeological material at hand to perform any dating then we are indeed relying on the c14 datings thank you are there any other questions to the speaker I do not see any other questions okay so Janikael thank you again for this very interesting and very well prepared talk about urban archaeology and how to excavate human past in the cities I do not know if you call this field work or urban work it is difficult to say but there is a lot of field work involved of course even if it is a very small trench we always try to be there to take our samples so there is a lot of field work involved but there is also a big part which is afterwards the laboratory work all the microscopic work that we have to do chemical analysis it is basically a combination of both so now I think I will close this very nice session we had today and I would also like to thank Jean Luc who made the first hands-on activity and made this very nice introduction about using in the classroom seismic events of the past in the city of Rome I would also like to thank my old friend Carlo for his very nice virtual tour to Machu Picchu and since we all operate now virtually it is like if we visit also Machu Picchu this year instead of visiting a museum in Vienna which we do when we have a live session so I wish everybody a nice afternoon and we will convene again tomorrow at 9 o'clock in the morning Central European time so goodbye everybody for today have a nice afternoon or morning depending on where you are