 Hello, we are going to switch to something different now. You have built mountains with Shredar, you've torn down mountains with Shredar, and then you've seen where they go down to the coast with me, and now we're going to start becoming historians. A lot of the job of a geologist is to read the past, to find out what it tells us and what we can do with it. As you know, a lot of people make you take history when you're going to school because they believe that if you know where you came from, that it helps. If you know what's possibly, if it happened, it has to be possible. And so learning about history is a useful thing. And so now we're going to start looking back into history and see if we can tell time, see if we can tell stories, see if we can find out how the environment works. We're going to do a lot of this by looking at sedimentary rocks. We're going to look at what happens to all that sediment that's washed down the river before it gets some talk that interrupted again. And we're going to do this by trying to tell time. We're going to try to sort out time. We're going to start looking at some pretty pictures because we've got to look at pretty pictures. We've got to go to National Parks and have fun. And so we're going to start out with the cause class at Arches National Park. Arches sits just outside of Moab, Utah. It's a great town if you're into mountain biking, if you're into a whole bunch of things, you can go to Moab and have a good time. Our National Parks just scattered all around the place. And Arches is certainly one of the prettiest ones. Here at Shredar, as you certainly recognize, and behind Shredar are the LaSalle mountains. Way up in here are the LaSalle, and LaSalle is salt, the salt. And down deep underneath this, there are salt deposits from an old sea that dried up. And salt, when you squeeze it, gets soft and it moves. So the rocks in this area have done a little bit of this over time. And by doing a little bit of this, they've given us some very interesting things. And in particular, they've given us the arches. If you move underneath a really hard rock, these are hard sandstone rocks from a giant dune field that looked like the Sahara way back when, if you move underneath really strong rocks, they tend to break. And so whether you're looking diagonal in the bottom picture or you're looking end-on in the top picture, you can see that as the salt underneath moved and the rocks flexed, they broke. Whenever there's a crack, the world can get in. It can go beat up the rocks. It can try to change the rocks. And in particular, we're now underneath looking up. And you can see the blue sky way up there in the corner. And you can see where a rock has been cracked. The yellow arrow is pointing at it. And I'm going to draw you a red arrow that points at it too. You can see where the rock has been cracked. And then these funny looking streaks coming down the side of the rock. Water is dripping through the crack. And as it does, it carries sand away. It causes chemical changes. And eventually, the rocks are going to fall off there. And as the rocks fall off, they make these beautiful structures that we know as the arches. Here you can see a couple of places that arches have started. They haven't broken all the way through, but they started. You'll see on the right where Raya is sitting in front of a big stone arch that's sort of arching up over the top of him up there. And the rocks have fallen out of that hole. And it's fallen down the hill here. These big chunks behind Raya came out of that arch. They fell out. And on the left is, that one is in Buncanyon. And on the left is one in Canyon de Chey, where the same thing has happened except the stream has washed the pieces away. And so you get this sort of action. You get cracks. You get weather working down the cracks. You get rocks falling out. And eventually, they break through. And you get glorious beautiful things. You can see Shridhar in the very far lower left of the left-hand picture sitting down there. And he is looking at Delacanarch. It's one of the best icons of the National Park Service sitting up there with the mountains framed behind it, just a glorious place. If you look closely at the rocks of Delacanarch, you will see, hey, that the sand, the sandstone, the sand that's glued together by hard water deposits. And B, you'll see that they have layers in them. In fact, they look just like a sand dune that's had the sand glued together by hard water deposits. And that is part of the story that we're going to be telling here in a little bit, is how sediment turns into sedimentary rock and then what we can do with it. This is Landscape Arch. This is the longest natural stone arch in the world. Landscape Arch is probably not that long with us. You'll notice it's getting very, very thin in places, such as that one. You would not want to be under this one if things were shaking and baking just a little bit. Because if you look underneath Landscape Arch, you'll see a huge number of big rocks that have fallen off. And Landscape Arch is slowly caving in. A very large one fell off fairly recently, the last couple of decades. And the scar is shown in the lower right-hand picture. So down here on the very far right-hand side is where a bunch of rocks fell off. And you can see the rocks that fell off sitting down underneath it. And so the thing is slowly changing. The parks really are active. Geology really does happen. Now, this is a picture in Hidden Canyon in Zion National Park. It's one of the most beautiful places that you can ever imagine. It's a little bit south and west of Arches. And you go up in this canyon, it's glorious. And you walk back there, there's a long distance. And there's sand on the bottom. And the sand has little ripple marks in it from when water flows in the occasional rainstorms. And so you see things like this. It's loose sand sitting on the bottom with its ripples. This is sand stump. And all this is is loose sand that's been glued together by hard water deposits. And so you go from sand to sand stump. When does it change? Well, there isn't any set line. Just about everywhere, you get a little bit of hard water deposit put down. And at some point, you say, this one's hard enough that I'm going to change the name. But there's no real strong line. We find all sorts of gradations between sediment, sand, or mud, or something like that, and sedimentary rock. And so let's go and look at that just a little bit. So we will switch over and we'll write a few things. And so we are going to talk now about sedimentary rocks. You metamorphic rocks in Rocky Mountain with Shredar. You met igneous rocks belching out of volcanoes. And now we're going to look at sedimentary rocks. We tore apart the igneous. We tore apart the metamorphic. We made mud. We made sand and all sorts of things like that. And now we're going to see what happens to them. So you saw that weathering happens. And when weathering happens, which is just weather beating up on rocks, it gives rise to a couple of things. It gave rise to clasts, pieces, chunks. So clast is a fancy geological world, but chunk will do fine. And we also saw that it gives rise to dissolved salts. It's stuff that you can't see that breaks down into individual ions and washes away to make the ocean salty. So it gave rise also to dissolved salts. And so these are the two things that come out of weather beating up on rocks. And so you can imagine that they don't always go immediately to the ocean, to the subduction zone, to the volcano. They may stop on the way. And so if they stop on the way, if they're headed from here to somewhere, and they end up stopping for a while, then we call it sediment. So if they stop somewhere, the stream puts them down, the glacier puts them down, the wind puts them down, whatever, if they stop, we call the pile sediment. We call it sediment. And so you can imagine that this is going to turn into sedimentary rock at some point. And to turn into sedimentary rock, you have to make it hard. So if you take sediment and harden it, hardening sediment makes sedimentary rock. Hardening, that's not a technical term. The hardening sediment, but we'll give you some technical terms here in just a second, the hardening sediment gives sedimentary rock. And there is no, we changed the name Nature Dozen. There are all possible gradations between sediment and sedimentary rock. And at some point, we feel compelled to say, that's too hard. I'm going to change the name. There are several processes that go into this highly gradual transition. And it certainly is a gradual transition, a gradual change that takes one to the other. Up here above where I am, if you take your rock hammer and you hit a sedimentary rock, it goes boom. It's really hard. I have a friend that was studying sedimentary rocks that had been scraped off of the slab in Olympic National Park. And what they call rock, they wanted to study erosion. So they'd go out and hammer nails into it and then watch how fast the nails were washed out. And so there's very, very much softer than ours, but they both were called sedimentary rocks. And so we have this gradual change of one to the other. And it is achieved primarily in three ways. The easiest one for doing this is how you harden it, so the hardening of sediment. The easiest one to think of is probably hard water deposits. Most people these days have soft water. And if you have soft water, they've taken most of the rock out of the water. And you don't notice that your pipes get clogged. But you know something in an old house, you call the plumber. And you say, I need help with my faucets. The plumber doesn't come in with a little screwdriver. The plumber comes in with a big wrench. And the plumber's got a big wrench because all the pieces are stuck together. And all the pieces are stuck together because whenever you put water in contact with stuff, it dissolves something here. And it puts something down here. And there's usually bugs living in it, microbes that are changing the chemistry. And so you end up with anybody that's ever tried to take apart plumbing knows that it's stuck. And it's stuck by hard water deposits. Whenever you've got water in it going, whenever there's a light, there's chemistry. And whenever there's chemistry, you're taking stuff from somewhere, and you're putting stuff somewhere else. And eventually, you're going to end up gluing things together or else dissolving things are getting rid of them. And so we always see this in human activity. It's stuck together. Nature is the same way. If you leave a pile of sand long enough, and you don't stir it, and you let water go through it, eventually, you'll find out that minerals get deposited in the spaces. And it's stuck together. And once it's stuck together, we say, oh, that isn't a sediment anymore. Now it's a sedimentary rock. It's easier if you squeeze it at the same time, because that keeps stuff from moving around. And so you may also see squeezing going on or compaction. If you pick up a handful of sand, and you squeeze it, you won't make it stick very well. You're not strong enough to do that. If you're at the bottom of the Mississippi Delta, it's seven miles of mud on your head. And it's pretty hot down there at the bottom. And if you put seven miles of mud on your head, you get squeezed. And so that will help solidify things. Way down at the bottom, where it's hot and things are getting squeezed, you start to see new crystals grow. Things will dissolve. Other things will deposit. You'll get what we call recrystallization, or the growing of new minerals. And you'll be sitting there and say, OK, he's talking about growing new minerals. He's got a fancy word for that, which is recrystallization. What's the difference between this and metamorphism? And the answer is nothing. We humans have to draw lines. And if it sort of looks muddy, we call it recrystallization in a sediment. And if it looks pretty, then we call it a metamorphic rock. And we change the name. But then this sort of grades into metamorphosis. You heat things, you squeeze things, and they start to change. The biggie for making sedimentary rocks is really probably the hard-water deposits. We actually have a fancy name for that, as you might imagine. We call it cementation. You're putting cement between the grades. And so cementation is usually what group glue sediments together and make something different. Now, let us then go look at some more sedimentary rocks. So we'll switch over to the pretty pictures again and see if we can go there. This is, it's so hard to pick a favorite part. They're also wonderful. But if you want a beautiful, fairyland, wonderful, just unbelievable place, go sit at Bryce for a day. You know, sit on the rim in the morning when the sun gets up early and watch the sun come up on Bryce. Sit there in the evening and let the sun sink behind you and the shadows lengthen. It is just an amazing place. It is a place that is hard to believe that anything can be so pretty. The flowers are there. The mountain lions are there. You know, all sorts of wonderful things to see up on the rim. They got green dogs and deer and what have you. You go in the winter. And if you can get in, the last time I was there in the winter, they were loaning out snowshoes at the visitor's center. And you can put on your snowshoes and you can get snowshoeing along the canyon. It's just an amazing place. The scale of it is immense. If you look in the right-hand picture here, you'll see at the bottom a whole bunch of people. I'm circling one of the cause students right here. I came to see which one. Because you'll notice that this is big place. And yet it looks so delicate. It looks so beautiful. Now, you'll notice in all of these pictures that you see layers. The rocks are layered. And that is common in sedimentary rocks. You wash something in. It's put down. You wash some more in. It's put down. And so you end up getting layers in the sedimentary rocks. These happen to be from a lake. Today, there's a little lake left in Utah, the Great Salt Lake. During the Ice Age, when there was less evaporation, there were a lot more big lakes that extended across many places in Utah. And as we look back in time, we see the deposits of many lakes. And so the Bryce Lake, or there's various names given to this, was this big lake that sat down in Utah. If you look carefully in many of these rocks, especially some just a little farther north of this, you will find fish fossils. You will find flamingo tracks. You'll find little snails and all sorts of things that say, OK, this was lake. It was water. It's glorious. When nature starts beating up on these rocks, it just carves such beautiful things that it's hard to imagine. Here are a couple of our cause students down here, Sam and Samir, looking at a couple of really big trees that are sitting at the bottom of the canyon. It's hard to imagine how they live there, but they're doing just fine. Thank you. I don't think they do this anymore, but if you remember, we've talked about sediment being carried in rivers and along beaches and so on. Here's a case that a stream is flowing towards you. So the stream is coming towards you. Now, there isn't much water in this stream right now. It only flows when it's raining. And the trail was getting buried in sediment. So the Park Service put these big logs across the stream. And you'll notice what happened is that sediment is piled up above the logs. It spilled it in. And there's actually been erosion down here below that's cut down a little bit. So you can see the dynamics of sediment, what you've learned in earlier units, keeps carrying through. If this were to sit here a long time, you would get hard water deposits and it would start to become a rock. It isn't there yet. It's still fairly loose. This is a very interesting slide. Dave Genesco of the cause class and I had the good fortune to go up and look at this one. And this one feeds into a story that we're going to tell about reading history, about inferring what happened. We are just outside of Bryce. We're down in Red Canyon and the place I used to shoot a lot of westerns. And we're up on the same rocks that Bryce is made out of. Now, Bryce is mostly like sediments and you find all these fish fossils and stuff in similar rocks around. And occasionally you'll find such things in Bryce. But if you have a lake, there's probably a river feeding into it. And so in fact, as you go west out of Bryce, you find the deposits of the rivers. We know sort of what a river gravel looks like. If you've ever been down to a river that has a little gravel bar in it and looked at the rocks, you know that they sort of look like this picture you see on the left. The rocks tend to be rounded. Rivers break off the hard points. And so after a while, river rocks tend to be rounded. The big rocks, cobbles we call them or pebbles, will have sand sitting in the spaces between them. This thing just looks like a river deposit. It's shaped like one is shooting down from a mountain range to the west, headed down into the lake that was Bryce Canyon. And so this is a sort of deposit that a geologist who has looked at a lot of rocks will be able to say rivers make this and it doesn't look like anything else I've seen. The size, the shape, the arrangement, the rounding, the sorting, all the things that go into this are pointing to this being a river. What's very interesting though is that one of the pebbles in that river, which is this orange one in the middle here, one of the pebbles in that river is itself a river deposit. You can see that this orange one that I'm sort of drawing on over here is made up of little rounded sedimentary rocks itself. There's a big story in this and it's a story that you should start thinking in your mind. How am I gonna tell this story? What is it that has to happen that I can have a piece of an old mountain range and a piece of mud that's been squeezed and a piece of an old beach that has been put together in a river, bounced along, their corners knocked off, had sand deposited around them. Then they've been glued together by hard water deposits enough to make them hard. Then they've been broken out, they've been bounced around in another river until they get rounded on the outside. They get deposited with pieces of all sorts of other things, old mountain ranges and old beaches and other things. They get glued together by hard water deposits and they're sitting up on a cliff far above any stream on the outskirts of Bryce. There is a big story in this and it's a story that, like I say, you wanna start thinking about how you would tell that story and what it would mean. So let's go back over to drawing things that might possibly prove useful and what we're going to do now is we're gonna take a little look at sedimentary rocks such as the ones you were just looking at. So we saw that sediment is either pieces, it's clasts, or else it's dissolved stuff, it's salts that dissolve. As you might imagine then, the sedimentary rocks that are produced from sediment come in two basic types. They either are pieces or they are the dissolved stuff that is put down. And so we see chemical precipitates. If you take a handful of ocean water and you let it evaporate, you will get a handful of salt a little bit. If you were to wash ocean water into a little shallow basin next to the ocean and then close it off and let it evaporate, you'll get a layer of salt. If that happens a few times, you'll end up with a lot of salt. We saw way back in the beginning that valley early mining was for salts. It was actually a particular salt that had borax in it that had washed out of volcanic rocks. The water is carrying the dissolved stuff. It goes down in Death Valley, the water evaporates, it leaves the salt, and then people went in and mined that. And so chemical precipitates include things such as salt. It includes things such as the borax that led to the 20 yield teams in the early mining in Death Valley. And so these things happen, you usually find them in fairly dry places because when it's wet, the salts tend to wash away. Other kinds of sedimentary rocks we can do them in a different color to have more fun. The other kinds of sedimentary rocks are the ones that are made of clasts or pieces, and so we call them clastics. And they are classified in various ways, usually by the size of the pieces. And so if you go in and you have a bunch of sand and you glue it together, you say, oh, it's a sandstone. This is really highly technical, let me tell you. So sand gives rise to sandstone when it gets hardened up that we decide we want to change the name. A little bit smaller than sand, we have something called silt, and silt gives rise to siltstone. And there are actually very technical definitions for these things that you don't need to know. Silt is 116 to 1,256 in a millimeter in diameter. Sand is 116, y'all, so on. If you have clay, it gives rise to claystone. That is less than 1,256 to 1 millimeter in diameter. This is little stuff. Although usually people change the name. They use an old name for claystone, they call it shale. And so you may possibly have come across that as one that you're familiar with. If you get things that are bigger than sand, there's granules. People don't usually talk about granules stone. They get pebbles and they call it pebbles stone and they get cobbles and they call it cobblestone, but usually if you've got bigger pieces, they say, oh, let's just call that a conglomerate and we'll not worry about that. And so you'll end up with these being the main heights of sedimentary rocks. What they are, how big they are, whether they're evaporated or not, whether the corners have been knocked off, a whole bunch of things of these rocks tell you a lot about the environment in which they were deposited. And so what we can now do is look in a little bit and we can say that sediments and the sedimentary rocks that they turn into reveal the environment in which they were deposited. And now you can start to see that if we can read the environment, if we can tell what the conditions were in which it was deposited, and we can read time, which came first and which came later, we can tell history. We can tell what the earth was doing and how it was changing. For example, suppose that you go down and you find a rock and you crack the rock open and there's a fish fossil inside. It's not terribly likely that you're looking at a desert sand dune. You're probably looking at something that had water. And so what you can do is you start looking at things such as fossils and fossils are pretty good indicators of what's there. If you see lizard tracks, you're probably not at the bottom of the sea and you might be out on the sand dune somewhere. If you see ferns pressed in a coal, you're probably not out in the desert where it's too dry for things to grow. And so fossils are going to give you a lot of clues as to the environment. And there's a big difference between a fish and a fern and a lizard and so on and so forth. And so you can recognize these things and you can start reading them. There's other stuff. If you see a pile of boulders, the wind did not blow them there. We never see wind quite strong enough to peg up boulders and put them. Now glaciers can bring piles of boulders. And so you start saying we can look at what it's made of. A beach is all sand, it's sorted, all that going in and going out and washing away. The little pieces are washed away fast. The big pieces are left behind until they get broken up and the beach makes the sand-sized ones, the in-between ones. And so we start looking at the size, the shape, and the sorting, whether they're all the same size or whether some of them have been mixed with other sizes. So the sorting of the sediment, like the size, shape, and sorting of sediment, clearly has clues to what you're looking at. Landslides may include all sizes. Glaciers can carry all sizes. Wind does not, wind is very selective. Little tiny ones get blown far away. In-between ones make sand dunes, big ones are left behind. And so when you see sand, it's usually wind or it's a beach, something like that. And so these are pointing to indications of the environment. Structures in the environment also can give you indications. If you see mud cracks, the mud dries and it cracks. You've got an idea that this was sitting in a place where it could dry so it could crack. And so when you see mud cracks, you can start to tell a story. You see rain drop in for this. Wow, it was made when the rain fell on the mud. And then more mud washes in and varies it. Moraines, if you see the pile left by a glacier and all the scratching and polishing that glaciers do, you're not in the middle of the tropics in a hot place. And so if you see moraines, that is pointing to something else. And so we can do environment by looking at the sediments and what is there and what is doing. If you can do environment, environment, add time, and you can do history. So that's where we're headed. We wanna tell the history of the planet. What was where? Where were the continents? Where were the rivers? Where were the glaciers? Was the climate changing? Who was living here? And so we're gonna try to put time together and we're gonna see what we can do. Now to do that, let me show you a couple more pictures. So we will flop back over to pretty pictures. And I gotta get a little bit here. Warmly, you dump some mud. You dump some more mud. The youngest stuff is on top. Nature doesn't raise the lid and shut mud underneath. You put layer on top of layer, on top of layer, on top of layer. If you're on the flood plain in the Mississippi, you build your house and the flood comes in and it puts mud on the grand piano. The mud is young gripping the grand piano. The grand piano was there and then the mud is put on top. So normally they pile up and we can do a story. The young one's on top and the old one's on the bottom. There is however a bit of a tweak to that which is occasionally nature causes trouble. And you remember in an abduction zone you think can cram things together and if you cram things together too much that they'll start to bend and if they bend too much they'll roll over. And if they roll over now we gotta make sure that we know which way was up originally. And there's a picture over here that we got on the left and if you follow one of these layers start down at the green place, down at the bottom and then follow that layer around and look it bends and now it's upside down at the yellow place. And so geologists can't just say the young one's on top because occasionally nature tries to throw us a ranger. Fortunately we can tell. There's all sorts of things that say this is the direction that was up when I was deposited and a geologist reads these and then they can say, okay, am I down in the green place and I'm still right side up and the young ones are on top or am I up in the yellow place and I'm upside down and the young ones are on the bottom. And so there are many of these indicators. Something has to be before you can cut it. You know, I could cut a piece of paper that's fairly easy but I can't cut it before it's made. And so what we have here is a picture taken in a cliff, it came in the shape and this is a fossil sand dune. And when there are sand dunes the wind blows sand and the sand piles up and makes little layers and so you'll see little layers here. This picture is only about six inches across but you'll see layers that have piled up. The red is actually hard water deposits, it's rust that's been put in here. And so the wind was blowing into this picture from the right to the left and it put down these various layers that you can see in the picture. Then the wind picked up a little bit and it cut the top off. And so all the way along the top there you can see the layers go up and then they're cut. They just end right there and then there's more layers deposited on top of them. And so this one has to be right side up. The old ones have to be on the bottom because they've been cut, they've been walked off on the top by the wind that put the next layer down. Now I can play games with this. The picture that you just saw is now in the upper left and the blue arrow shows which way was up where the sky was when this sediment was deposited. Suppose that mountain building came in and it started turning things over. And so you can look to the right of it there and I've taken the picture and I flipped it on the side and you can look farther down and I've taken the picture and I turned it upside down. All of these are possible. Nature can do this. But you look at it and you say I know because the cut is still there. And so I know if I come to the upper right picture I can see where the layers are cut. And so I know that the layers had to be there before they could be cut. So I know which way is up. I know what the point is. This is a picture in the wall of the Grand Canyon. You're down at the south rim, you're headed down to the bottom and you're gonna have a great time and you look up at that cliff and oh man, it's such a wonderful cliff. This picture is probably a hundred feet high. This is this immense, immense cliff that's sitting there. On top are sand dune deposits. It's a giant, giant sand sea that came in here. On the bottom is a flood plain deposit. You might think of the Nile River flooding across its vast delta, its vast flood plain, and then the desert of the Sahara blowing in over the top. And so the bottom rocks are flood plain deposits. You'll find leaf fossils in them, you'll find footprints in them, and then on top it turns into these sand dune deposits. Now you'll notice right under the red arrow that the sand goes down a crack. The mud, if you've got mud and then it dries out and this huge drought arrives and the mud starts contracting, it'll crack. And when the sand blows in, the sand will fall down that crack and you can follow the sand way down this crack. This picture has to be right side up. Sand does not fall up cracks, it does not fall sideways in cracks, it falls down cracks. And there's the sand and there's the crack and there it goes, this picture's right side up. If we turn it on the side, you'd know that. You're now, G-side Ted, you're geology and national parks wise, you can figure this out. These are other mud cracks, these are also right side up. This is from rocks that are just like rice except just a little bit north and the flagstaff lines down, the cracks are going down. And so it cracked and then more mud will fall in but we can see down into these cracks as soon as the right side up. This one is a little tougher because it's a little hard to see but you'll notice my finger in the picture in the lower left and you'll notice the shadow of my big finger. And you'll notice the mud cracks up there in the middle and you'll notice the shadow of the mud cracks right there and right there. So these are sticking up at you. This is the stuff that fell down into a crack that was below it and then we turned the sucker upside down. And so we're looking at the bottom of this one and I'll draw this for you in just a minute after we walk through this. And so this one's upside down. This is, we're now at Sunset Crater, a big beautiful volcano and the lava came down and then it threw these little rocks and the little rocks that it threw actually made mulch for the native peoples that lived there, the Sinatra and they had wonderful times for a while because their crops didn't dry out because those little rocks held the water. But in the lava flows, you know when a lava flow comes down it's usually bubbling and burping and belching and sorts of things and the very top will freeze because it's in contact with the air and that freezes it and the bubbles rise. And so if you look at this one you'll see big bubbles at the top and when you go down there's little bubbles and then there's not many bubbles at all. This one's right side up, the bubbles rose and they got trapped under the top and it doesn't always work but this one usually works too. And so this says it's right side up. If later the mountain building turned it over you would look at that and you say, I know what's going on. Okay, so let us draw a couple of those. Just so we're on the same page and you're sure and this might prove useful someday. Suppose we start out and we have water and it washes in some mud. So down here we have mud and up here we have water and you've got fish swimming in the water. So you know which way is up. Okay, and now what happens? The fish swims away and the mud dries up. Okay, so now we're going to dry this up. This fish is going off somewhere downstream and after the fish swims downstream to safety then the water dries and what happens after water dries is usually it will crack and so you'll get mud cracks. And so there we have a picture of some cracks. The cracks go down, they end, they don't go to the center of the earth and so the cracks go down and they end. Now what's gonna happen? We're going to wash in some more mud of some other kind. Let's make blue mud and so more water comes and the mud comes in and we get another layer in here and what does it do? It spurs down in the crack. Okay, if you see this in a cliff, you say, oh, it's right side up. There's no problem. If you happen to come to a cliff and you happen to see something that looked like this, let me see if I can get this. Suppose that you saw it this way, okay? And it was looking something like this. You would look at this and you'd say, oh, no, mud cracks didn't do that. The mud didn't start with a giant overhanging cliff with cracks going up into space. This thing has been flipped over. So this has been flipped. Okay, so this one is right side up and the one down here has been flipped a very funny way. You know, it's not flipped quite all the way over but nature doesn't do that. Sometimes it flips it all the way. Sometimes it flips it three quarters of the way. There's all sorts of possibilities of what nature can do with these things, okay? The same thing would do if you had footprints. If you had a dinosaur foot, you could even think of these as being, you know, if you wanna think of that as a footprint rather than a mud crack, it's the same sort of picture. And so footprints do the same. Footprints go down. Raindrop imprints, if the raindrop falls in mud and it makes a little hole, that goes down. Bubbles rise in lava flows and they're trapped just below the top because that chills very early. They're trapped below the chilled upper layer, the chilled top. People often look at shells on this. If you go down to the beach and this will be interesting for you to do, this is not a hundred percent, but it usually works. Suppose that you have a shell sitting on the beach. Beach, okay, and this is a shell and here's a seagull flying over. Yeah, okay, big shell. Now what happens when the wave comes in? When the wave comes in, it's gonna get under this and it's gonna rock it. And so this is what you would call your unstable, easy to rock position. All right, well, what's gonna happen? It's sitting there and it's gonna rock back and forth and eventually it's gonna flip over. And so it flips and now it's sitting here and then it gets buried in the beach and it will stay there. And if you go down to a beach that has lots of curved shells and you look at them, you'll find that most of them, 80, 90% often, are in this position. It's stable like this. And so most shells end up this way. They get buried and you can tell which way was up. And so there's all these things that are sitting there that are telling about it. Let me try to draw the one I showed you in the Club of Canyon, the Shea, with the way that sand dunes work. And so let's see if we can draw a sand dune. We'll make it a red sand dune. And so the wind we're gonna bring in this way. And so here comes the wind and what happens, you know how sand dunes are, is that they sort of, you know, there'll be a pile here, but they start growing this way. And so over time, the sand is blown over the top and it piles up in the lee of the dune. And so the dune builds out that way. And so it grows this way, grows sand there. Now what happens is there's usually changes in wind, sometimes just stronger, sometimes just weaker. And very often what you'll find is that the wind will come through and it will actually scour things off. And so you'll go, oh, that wasn't what I wanted to do. Okay, well, let me draw it back in. We'll erase everything. And so we'll go back and we'll say, okay, we've got this sand dune and it's sitting here and it grows along like this. And so here comes our sand dune and it's growing. Then the wind will come in and it will basically scour off the top. That gets cut away. And after that's cut away, you may bury this in another sand dune that's coming through later. And so now let's put some more through. The layers may be nearly horizontal. They may grow like this. But what you'll find is that where the cut is, these things will always sort of grade into what's underneath them. They won't be cut, whereas the ones on the bottom will be cut. And so the top ones are not cut. It's got to be there to be cut and the bottom ones are cut. And so whenever you see cut and not cut above it, you know which way is up. And so there's an indicator there that you're dealing with up and not up, okay? The other thing one notes is that indeed most layers usually start sort of horizontal, be slant, but they don't make cliffs. You'll never go out and see a giant 100 foot height cliff of sand. You'll see sandstone, but not sand. And so what you'll also find is that most layers start out nearly horizontal and they start out nearly horizontal because of mass wasting, otherwise they flump down. So that now gives us enough tools to tell stories. We can read environment. We can tell what the deposition was, whether we're a glacier, whether we're a lake, what have you, and we can read time. We can put events in old order from oldest to youngest. If you do that, a very, very remarkable result comes out. And this is something that was developed first by a canal engineer. This canal engineer, William Smith, was out trying to do canals and he was trying to work in England and he found that there's a lot of sheep in England. There's a lot of grass in England. It's sort of hard to find the rocks. And he'd find the rocks in a few places and they'd look around at the rocks and he started realizing that when he put the rocks in order, that he put the fossils in order. That there was one kind of fossil here and another kind of fossil there. And it also turned out that some of the fossils, actually he'd find in the dirt and he could identify from a fossil which rock was underneath. And so there was this canal engineer and his name was Smith. A canal builder named Smith in England and this happened in the early 17th century. And what he found is if you put the rocks in order, it puts the fossils in order. What does that mean? It means that the fossils that are near each other in the pile of rocks are similar. If you do the same environment. Now let's be very clear. You don't get exactly the same things if a lake turns into a sand dune. You sort of have to compare a lake to lake. But if you compare a lake to lake or ocean to ocean or something like that, what you find is the fossils that are near each other are similar. The fossils that are farther apart are more different. The fossils on top are more like the things that are alive today. And the fossils on the bottom are more different from the things that are alive today. And so what you find then is that the rocks of similar age have similar fossils. The rocks of very different age have very different fossils. So different age, different fossils. And the rocks on top, the youngest rocks have fossils that look most like things still alive. And so the youngest rocks, the youngest fossils, look most like things still alive. Now this was done for purely practical reasons. This is an engineer looking for a shortcut as to help him identify the rocks that are down underneath all the sheep and the goats and the heather and what have you. This clearly turned into something much bigger or helped contribute to something much bigger that we're going to talk about. We will come to that in just a little bit. Right now we just need to add a couple of things. One is that this gained a name. It was called the law of faunal succession. Now this is not a law that was passed in Congress. This is just a rule that is found to work over and over and over again. And after you check it 10 times, you check it 100 times, you check it 1,000 times, and it just keeps working. And eventually you say, well, this works. And so we should give it a fancy name so that people know that we checked it a whole lot and the thing keeps working. So they call it a law. But there's no law here. It's just a summary of observations. It is the law of faunal succession. Another thing that came out of this, and this will be the last thing we need to get through for today, is that when people had put all these fossils in order, they got really tired of talking about, well, you know, the time that they had those big, clunky trilobites with the giant eyes and the little horned corals. But not after you showed up with the big, gritty clamps. They needed names. They needed some way to talk about this, aside from talking about big, clunky eyes and trilobites. So they came in and they named everything. And you know that geologists and scientists in general have a habit of trying the name of a lot of things. And so they gave their names. And if we go from young rocks on the top to old rocks on the bottom, the big names that they gave it, they said, OK, today we're going to call the senozoic. All right, now, you'll recognize in the word senozoic, zo, for life down there. Seno is actually something like new. And so this is the time of new life. There are lots of things alive today. There are insects and all sorts of things. But sort of the big land critters are more mammals than anything else. So you'll often hear this called the age of mammals. Although, if you've ever been out in a really mosquitoy place, you begin to wonder about that. Now, below that, they said, well, there's different things. We need another name for that. We don't see mammals dominating all the way back. So below that, they called the mesozoic. And meso is middle. So this is something like the middle life. And the big land critters, this is bias for us, big land critters. So this is middle life. And the big land critters were dinosaurs then. So this is what you often hear as the age of dinosaurs. Now, below that, you might imagine, if we have new life and middle life, well, let's have old life. So let's call it the paleozoic. And so this is something like the old life. There weren't a whole lot of land critters until the latter part of this. So this is old life. And if you want a catchy name, you could call this the age of shellfish. Because there are lots of marine life that's making shells. And we have good records of that. Below that, there are a bunch more zoic words. If you were taking, of course, a historical geology, we'd pop them in your head. We're going to use an old term that's a little easier and lumps a whole bunch of them together. We're going to call it the precambrian. It turns out that the paleozoic and the mesozoic and the zenozoic have subdivisions. And one of the subdivisions of the paleozoic is named for whales or cambria in the United Kingdom. And the rocks that are exposed there have these cute goggle-eyed trilobites, since they call that the cambrian. And then this is older than that, so it's the precambrian. And if you want, that's just the rocks that are before the cambrian, so don't worry about that. And there isn't a lot there. A lot of algae, blue-green algae, cyanobacteria, various other things. So let's just call this the age of algae. That is a little bit loose, but I think it'll get us there. So we have come a fair distance here in a very short period of time. You see some beautiful things. I hope that you enjoy seeing these. I certainly enjoyed going there with the cost students to take the pictures. We have seen that sediment, which is washed down from the hills, which is landslided down, which is broad-bred glaciers or what have you, can be glued together by hardwater deposits to make sedimentary rocks. We can look at those and say, are you a sand dune? Are you from a glacier? Are you from a landslide? Are you from a lake? We can put them in order. We can tell if nature is trying to fool us by flipping them upside down. And so we really can say, this one's younger, and this one's older. We can put the events in order. And once we do that, we are going to start telling histories. One of those histories is going to involve who lived where, when. Some others are clearly changes in where the continents were. They're going to be changes in all sorts of things in the climate. But one of those stories is going to be who lived when. And we've got a few words now down here that sort of help us summarize who lived when. Notice that we don't have any numbers on this young and old. And so we have to go look at the putting numbers on the young and old before we can go further. And it's a further. So that will be our next task is to try to put years on this. And then we're going to tell history.