 It's 1 o'clock on Tuesday, April the 19th. So you must be watching Science at Soast. I'm your host, Pete McGinnis-Mark, and every week we bring in an exciting new student to tell us about their research. Soast stands for the School of Ocean, Earth Science and Technology at UH Manoa campus. And today I'm really excited to have Nafia Gaur Pasqualeon, who is a graduate student in Earth Science. And we're going to be talking about ocean research cruises. So Natalia, welcome to the show. It's great to have you here. I'm really excited to hear about the kind of work which you do, but maybe for the viewers, you can just say a little bit about yourself. Hi, everyone. Thanks, Pete, for the invitation. I'm very happy to be here sharing about my research today. And so I am from Brazil. I am currently in my second year of PhD at the University of Hawaii at Manoa. And I took my undergrad and my master's in Brazil. And all of my research has been so far related to volcanic rocks and volcanoes. So now I'm starting to study a little bit of sea mounts and underwater volcanoes too. So that's what I'm going to do. So that might explain if you're interested in volcanic rocks, why you've come to Hawaii, because it's volcanic islands. Yes, because when I was working in Brazil, I was working with the last Brazilian volcano, which is in Trindade Island. And after that, for my PhD, I decided that I wanted to go somewhere but I could be pretty close to an active volcano. So in Hawaii, I have this opportunity. Excellent. Good. Well, you mentioned sea mounts. And I think the viewers may not be that familiar with sea mounts being old volcanoes. Maybe we can go to the first slide and you can just talk us through. If you're interested in studying volcanoes, why study sea mounts? And here's a cartoon. What is it we're looking at, Natalia? Okay, so sea mounts, they are volcanoes that don't get out of the sea level or they can become sea mounts after being volcanic islands and submerging. So in this chart here, I'm presenting a little bit of how do sea mounts form. And there are some different ways that a sea mount can be formed, but the most famous, we can say one, is through a hotspot. Hotspots are columns of very hot, buoyant material that rises from the core mental boundary or from the lower mental and upper mental boundary. And once it reaches the oceanic crust, it starts to generate volcanism and to create these small volcanoes that if there's a continuous magma supply, then these sea mounts, they start getting bigger and bigger and bigger, reach the sea level, become volcanic islands. So if we consider that this source of volcanism is quite fixed or it doesn't really move that much in relation to the plate, we can think that if the plate is moving to the left, as we can see in the cartoon, then this source is gonna be imprinting volcanoes and once the volcano moves far from the source, from the heat source because of the plate movement, then these volcanoes are gonna start submerging. And this is what happened to the Hawaiian islands. It's happening right now. So... The viewers may not realize, but Hawaii is the classic place on this planet where you have this kind of hotspot volcanism and they might be familiar with the activity, say at Kilauea or Mauna Loa on the big island, but where we live, Oahu, of course, was formed the same way. And on your diagram, you had other examples, like Midway Island to our Northwest. That's a Hawaiian volcanic island, correct? And then the Midway is a volcanic island that millions of years ago was like Hawaii or if we go further to the Northwest, that is where we have other volcanic islands which are sunk below the ocean. And I would guess that the other thing which we need to point out for the viewers is, of course, that these volcanic islands move or are moved because the ocean plate is moving a process related to plate tectonics. Yes. Yeah, okay. So we see the arrow pointing to the left of the slide, Pacific plate motion. It's moving at about the rate your fingernails grows what I'm told, you know, a few centimeters a year or a couple of inches. So is Hawaii the only volcanic chain like this? No, actually, if you can put the next slide on. Okay. There are several hot, some different hotspot chains in the Pacific ocean and we rely, now I'm gonna talk a little bit more about my research, the focus of my research. So if we can try to track the plate movement from zero to 70 million years old, we can really rely the model in two hotspots. One of them is Hawaii and the other one is Louisville which is in the extreme south. These two, they are long-lived progressive chains of volcanoes and we can have a very good idea on how the plate, the Pacific plate moved for that period. However, if we go more than 70 million years, if we go older than that to up to 120, the current model relies on structures that are not very good for that because some of them they are not these long-lived chains of hotspots. So we went on a cruise to try to find the oldest portions of what we think can be the oldest portions of these two hotspot chains. Let's just backtrack and take another look at that second slide to help the viewers understand what it is they're looking at. This looks as if it's a map of the ocean floor topography. You've got North America to the top right, Australia to the bottom left, Asia to the top left and the colors just refer to the depth of the water would be my guess. Yes. So the island chains are the light blue. The white lines just show the trace of where the seamount chain is. Yes, thanks for pointing this out. I went straight to the explanation of the figure but for the ones who are not familiar with what I'm talking about this age progression, these straight white lines, they are highlighting the tracks. So if we can find two very good other long-lived hotspot tracks for the oldest ages, this will be perfect because then the model is gonna be much better. So we're trying to find the oldest portions of the Rurutu and Samoa hotspots which are in the middle of the Pacific here. And these oldest portions, they are assumed to be in the West Pacific seamount province. So that's where our cruise went. We went all the way to the West Pacific pretty close to the Mariano strange. We actually went over the Mariano strange. Which is the deepest part of the ocean for. Yes. And I think that in the next slide, we have a picture of the depth that we were like, oh no, this is just. So this is the research vessel that we were on board. And our research on board consists mainly first in mapping the seafloor so that we can find the best dredging sites and finally pick up the rocks from the seamounts that we think can be these oldest portions of these two hotspot tracks. And tell us about the Kilo Moana. I understand that's operated by the University of Hawaii. Yes. Do you know how big it is or how many people would work on that? That's the one that we see down at whatever it is, Pier 35, something like that on a regular basis, yeah? Yes, yes. I'm not sure about the size, the exact size, but I know that in terms of people, we had around 12 scientists on board and around 25 people from the crew. So. So 40 people. Yeah. And how long does it go out to sea? Is it like a couple of days or a month for? How long can it stay out on the ocean? So we stayed for 40 days on the ocean. Yes, 40 days. And but I'm pretty sure it can go a little bit longer without needing more supplies. But that is an impressive ocean going vessel that the university operates. Yes. Yeah, that's good. It's very good. It has some good installations for lab work we needed. So this was essential for us. Right. And I think we'll see some of the lab work later in today's talk. But you're trying to find the oldest part of the seamount chain that runs through Samoa. So how do you map, say, the ocean floor? How do you get? Where do you know where to go? Yes. So the research vessel is equipped with multivink but symmetry. And I think now we've got a slide. Yes. Very good. Yes. So if you take a look at the middle of the image that is in the center of the screen, there's a blue small triangle, a very, very small point that is following a yellow line. So this is our research vessel. And this is a view from above, let's say. And so towards the both sides of the cruise, here all this blue thing in the screen is the mapping of the seafloor. And if we take a look at the bottom image, which is more colorful, we're starting to see some topography. So we use the multivink but symmetry, which consists in sound waves that are emitted from the research vessel and then reflected back when they hit the seafloor. So we can calculate. We have the velocity and the time that the sound waves take to goes and come back. So we can calculate the depth of the water column and then the depth of the seafloor. So that the multi-beam people may have heard of sonar, sound waves passing through the water, right? And the symmetry, think of that as the height of the ocean floor, or at least the depth beneath the sea level, right? Yes, exactly. So once we map the seafloor, we can have a clue of which would be the best structure for dredging. So we can go to the next slide, please. So here we can see we were going around a crater, a submarine crater, which was awesome. So this site we dredged from the inside of the crater and a little bit from the outside if I'm not mistaken. But to find to say, hey, this is the point. This is the track that I want the cruise to go in dredge. You can go to the next slide. Just before we do that, in the previous slide, the colors that we are seeing on the computer screen presumably are different depths, right? So the brown might be the summit crater of the sea now. Exactly. If you take a look on the left, there's a number of 2,781 meters depth. So the top of the crater was in this depth. OK. And what's the goal? Do you go for the summit crater, which might be the youngest? Or do you go to the flanks on the old stuff? Usually we try to go to the deepest part that we can, because the cruise does a track. It goes through a track. So it goes from the deepest to the shallowest so that you can dredge through an upper slope. Yeah. OK. Yeah. The next slide can show a little bit more. So yeah, finding the best dredging sites. These maps, they are generated by a combination of the slope and the reflectivity. These ones are, yeah, it's a combination of the slope and the reflectivity. And when it's very, very red, it suggests that this would be a good place for dredging. So that's how we decide, oh, the cruise is going to be dredging around here or not. Presumably you don't want to dredge where there's thick sediment, I guess. Exactly. And that's why the reflectivity, the ability of the sputum to reflect sound waves strongly, might suggest that there are bare rocks there. Yes. OK. Exactly. Good. All right. So how quickly can you find a good place to go dredging on, do you dredge just once? Or how long does it take to hold a basket? Yeah, so it depends. Because sometimes, depending on the conditions of the wind and the waves, we really struggle to find a good dredging spot so it can take some time. And then once we really find a good spot, it takes a couple of hours to put the dredge down, I think, like one or two hours. Yes. And then it goes for a couple of other hours until the cruise is done with the track. Uh-huh. Yeah, we were dredging one. The next slide shows people on deck, right? And do you literally just throw the sample bag over? How does it work? Yeah, so it's not that simple just throwing the dredge basket into the water, right? First of all, you have to be wearing protective equipment. And this is just like a picture of all the women scientists that were on board. And we were so there are four people at least have to be on deck to put the dredge in the water. And there are some engineers that stay around to help us. And yeah, so putting the dredge is not so hard, but taking it back when it's full of rocks. I think the next slide is about, yes. So we have to literally fish the dredge basket, which is shown in this figure on the left. And then hopefully we have a bucket full of pylolavas, which are ideally the best ones for being analyzed because they represent submarine lavas. And they're not like sediments or they don't have fragments of sediments within them. So massive pylolavas would be the best ones. And we call them pylos because of their rounded shapes. They really resemble pylos. And these are exclusively formed underwater. So they're pretty cool. Can take a look in the right picture here. OK, but if you were trying to find the oldest rocks on any seamount, perhaps those lavas would have been erupted above sea level. Here you're seeing pylolavas, which were obviously erupted underwater. So would you necessarily think they are the oldest rocks from this seamount? Well, not necessarily the oldest because, I mean, these ones could have been formed a couple of years younger than the oldest one. But for sure, they were not super aerial. They were not from the stage when the volcano was above the sea level. Yes, so we can be happy about those. They're at least from the underwater stage. And is that a typical number of rocks that a dredge might actually pull up? It looks like a dozen rocks or something like that. They bring up fish or they bring up a whole range of other things. We had some different stuff coming up, such as shark teeth. We think it's a megalodon, like prehistoric shark teeth coming up. Yeah, but usually it varies a lot. Some dredges were full of massive rocks. Some dredges were almost empty, like with very few pebbles, which were pretty hard to accept because it takes so much work to find a good spot, put the dredge in the water and then take the rocks back. So sometimes it could be very frustrating. And do you get any hint? We saw trying to find the best place to dredge. Is there a correlation that you learn on your cruise? Which places are most likely to produce good samples in the dredge bag or not? Yes, actually, we have to avoid the flat tops, the flat surfaces in all the ridges of the volcanoes that are kind of connected to the flat surfaces. So it's better if you go a little bit further off to the side because the chance of getting corals and rocks that we really don't want gets. Yeah. And I think slide nine, the next one will show in more detail some of the rocks. So would this be a typical hall that the kinds of rocks you bring out? First of all, what is a higher class type? OK, so higher class types are types of fragmented rocks. How you can see in the left picture that contain fragments of basalt, usually pylolavas, mixed with other material that can be already in the seafloor or can be the alteration of glass, which we call pelagonite. So these are very typical as well, because once the pylolavas are erupted on the seafloor, the thermal shock is so high that lava skin fragments and generates these types of high alloclastides and the iron manganese nodules. They are very important because they can host a series of metal. There are interests for the industry, for like green technologies. So some people are very interested in mining the seafloor. We were not. So we were thinking this was just like for fun. And sometimes some of the rocks that we were are inside these nodules. So we could extract them. So your question in doing the dredging was to try and find rocks that you could age. How do you age? They I think the last slide shows us a lot of them on what you do. Right. Well, your research. Actually, I'm working with the isotopic analysis, gel chemistry analysis in our collaborators are going to be age dating. So my job is to use these short columns that are in this picture to collect some key elements that are going to give me some a magnetic signature like I can figure out what was the origin for the seamounts through this analysis and to obtain the ages of these rocks. Our collaborators are going to use Pledgeoclase or which is a mineral phase that contains potassium and they can date these rocks through potassium argon or argon-argon dating and or through the ground mass age dating. So that now to my way of thinking, there's a disconnect between the rocks that we saw in the previous slide. They look pretty big. How do you get a big rock into one of those glass tubes? Do you crush it or what's the process? Yes. So first of all, we use a rock saw and we cut them in several very, very tiny pieces like small squares. Then we crush them in like sand size. Then they have to be dissolved, leached. And finally, they're going to be in solution so that we can collect only the elements through these columns. There is a resin. And once we insert the samples in this resin, the elements that we don't want or that we want, they're going to stick to the resin and all the rest is going to fall. So that's how we can end up with what interests us or not. I would think of it in terms of maybe you add an acid or something like that. Yeah. To remove this until you weren't interested in. And that's what you have in the bottom of the tube. OK. Yeah. So where do you see this kind of research going in your own career? Are you going to forsake landlocked volcanic activity? Are you going to be an oceanographer or a green geologist? I guess would be the term. Well, so I still I'm still not sure of what I want to pursue for like after I finish. I'm pretty sure I'm going to take a postdoc. So I'm just not sure if it's going to be like with suba area of volcanoes or with underwater volcanic chains. And but I feel like this cruise has brought up my possibilities a lot. And I have a lot of interest in marine geology. So this is for sure a possible choice for my for my career. And are you going to try and stay in Hawaii? Or go back to Brazil? I don't know. Well, I would like to. Yeah, I would like to. But I'm hoping to all the possibilities that my show up. Well, it's certainly important to understand the evolution of the volcanoes that Hawaii is built from, right? But, you know, they're many older ones. But I'm afraid, Natalia, we've run out of time. So let me just remind the viewers. You have been watching Science at Soast. I've been your host, Pete McKinnis-Mark, and my guest today has been Natalia Gar Pasqualon, who is a graduate student in the Earth Sciences Department at UH Minora. So Natalia, thank you very much. Fascinating, happy sailing. I think will be a reasonable way to end. Thank you again for being on the show. And for the viewers, please join us again next week when we'll have another graduate student talking about their research Until then, goodbye for now.