US4 ROCKS
This eighth-grade science lesson is about rocks. It is the fifth lesson in a sequence of 11 lessons on the same topic. The lesson is 41 minutes in duration. There are 29 students in the class.
| Time | Caption |
|---|---|
| 00:00:08 | All right, let me show you something from yesterday. |
| 00:00:22 | Given enough time, and enough... depth, what's gonna happen to the sediments? |
| 00:00:33 | What's gonna happen, there Yolanda? |
| 00:00:35 | It's gonna become cemented. |
| 00:00:38 | That's good. |
| 00:00:43 | Now if- how are you gonna spot, how are you gonna identify sedimentary rock when you see it? |
| 00:00:54 | What's (it have)? |
| 00:00:59 | You have deposition. |
| 00:01:01 | Well, you're telling us certainly how it's made. |
| 00:01:05 | Yeah. |
| 00:01:06 | And, you know, that's certainly a good thing, all right? But I- I just want to come back to this. |
| 00:01:14 | Yeah. |
| 00:01:15 | You know, we know how it's made. |
| 00:01:18 | Sediments get deposited, buried and cemented together, as Yolanda tells us, and it forms sedimentary rock. |
| 00:01:28 | But my question is, how are you gonna spot it, how are you gonna identify it when you see it? |
| 00:01:36 | There's a lot of roads that are cut from sedimentary rock, and you can see it if you know what to look for. |
| 00:01:45 | What's that, Samuel? |
| 00:01:47 | When it- certain rocks might have layers on it. |
| 00:01:50 | Oh. |
| 00:01:58 | Let's see. |
| 00:02:02 | Like that? |
| 00:02:03 | Yeah. |
| 00:02:04 | Yeah. |
| 00:02:05 | Now, how do you know that's sedimentary rock? |
| 00:02:06 | Because it's- |
| 00:02:07 | How do you know? How do you know? How do you know, Nikita? Look at it. |
| 00:02:14 | Because it's stuck together. |
| 00:02:16 | How do you know it's stuck together? |
| 00:02:18 | Because it's in layers. |
| 00:02:20 | Say that. |
| 00:02:21 | Because it's in layers. |
| 00:02:22 | Okay. That's what- who said that? |
| 00:02:24 | Me. |
| 00:02:25 | That's what Samuel said. Absolutely. Absolutely. |
| 00:02:30 | So, you know, just in a cross-section, looking at it from the side, it appears like that. |
| 00:02:39 | All right. Now, how do you- why do you suppose you can see the layers here? Because if this river wasn't here, you wouldn't see the layers. |
| 00:02:47 | What did the river do to the rock? At least the sedimentary rock? What's happening here, Corey? |
| 00:02:53 | (inaudible) make stratas. |
| 00:02:55 | That's good. You know, the word- that's a good word. Another word for layers are strata. |
| 00:03:03 | Okay, but what did the river do to the sedimentary rock? |
| 00:03:10 | We did this. What is that, Eric? |
| 00:03:13 | It cuts into it. |
| 00:03:14 | That's right. So here's a wonderful example of a river- it's the Colorado River- cutting a canyon, |
| 00:03:22 | and in canyons, if the river is cutting through sedimentary rock, you could see the layer. Now, let me ask you this. |
| 00:03:30 | Suppose- and this was our little model from yesterday- suppose when the sediments got deposited in- in some ancient sea. |
| 00:03:44 | Sorry. |
| 00:03:46 | Suppose- suppose an animal, the remains of an animal, got deposited in the river along with the sediments. |
| 00:03:57 | So now we have an animal, you know, that could have been buried... a million years ago, 10 million years ago, 50 million years ago. |
| 00:04:10 | What do you think's gonna happen to that animal? |
| 00:04:17 | Rudy, what do you think? |
| 00:04:18 | It's gonna blend into the rocks, with the rest of the sediments. |
| 00:04:23 | That's right. Now, there's a word for that. There's a word for that. |
| 00:04:31 | What's that, Sonia? |
| 00:04:33 | Becomes fossilized. |
| 00:04:34 | That's good. Very good. |
| 00:04:43 | I'd love to pass it around, but since it's sedimentary rock- you can see the layers here- I'm afraid that it's gonna fall down and crack. |
| 00:04:51 | So I'll just come around. How do you like that, Terrence? |
| 00:04:57 | Like it. |
| 00:04:58 | Huh? |
| 00:05:12 | You did good yesterday, Antwone. All right. Now, let me ask you another question. |
| 00:05:19 | Suppose we dig down further into the sedimentary rock, into a layer that's underneath it. |
| 00:05:28 | Maybe- maybe this fossil of a fish is found in here, and maybe something like this- |
| 00:05:42 | is found below it. |
| 00:05:44 | What is that? |
| 00:05:45 | Well, it's called a brachiopod. And to us it looks like a clam. It's a shelled animal. If you had this fossil and you found it over here, |
| 00:06:03 | which would you say is older? |
| 00:06:06 | The one at the bottom. |
| 00:06:08 | Which would you say is older? |
| 00:06:10 | Um- |
| 00:06:13 | What would you say, Aisha- Angela? |
| 00:06:16 | I'd say the one (inaudible). |
| 00:06:17 | This one is older? |
| 00:06:18 | No, //the other one |
| 00:06:19 | //No. The bottom one. |
| 00:06:20 | Why is the bottom older? |
| 00:06:21 | Because it's more down. |
| 00:06:23 | That's right. |
| 00:06:26 | So I- so obviously the- the strata or the layers on the bottom are older than the ones on the top. |
| 00:06:34 | Now, you could use this. |
| 00:06:35 | This is how geologists go about figuring out what animal came first and what animal came second and what animal came third. |
| 00:06:45 | So it's almost like looking back in a book, where the pages at the bottom contain fossils that are older than the pages on the top. |
| 00:06:59 | All right. Now, let me show you something. Let me shut this. Corey, you want to get the lights for a minute? |
| 00:07:11 | Don't laugh. |
| 00:07:12 | Oh. |
| 00:07:14 | Sonia, I told you not to laugh. Oh. |
| 00:07:19 | I love your pants. Loving it. |
| 00:07:25 | All right. Any idea where I am? |
| 00:07:28 | It's- |
| 00:07:29 | Any idea? |
| 00:07:32 | Yeah, um- |
| 00:07:37 | Well, I don't mean the exact- I can tell you the exact location, but the type of landscape I'm on. |
| 00:07:44 | Ice. |
| 00:07:45 | No. It's not ice, Samuel. |
| 00:07:47 | It's a- |
| 00:07:50 | Sonia? |
| 00:07:51 | Is it a mountain? |
| 00:07:52 | It's a kind of mountain. |
| 00:07:54 | A cliff? |
| 00:07:55 | I don't know if you can call it a cliff. |
| 00:07:58 | It's a rock. |
| 00:08:00 | I'm standing on rock. |
| 00:08:09 | Sonia, got a clue here? |
| 00:08:14 | Delia. I'm sorry. |
| 00:08:17 | No. |
| 00:08:20 | Yolanda? |
| 00:08:21 | Maybe you're standing on a rock, and the sediments in the middle are eroding. |
| 00:08:27 | No. That's not how this hole got here. All right. Rudy? |
| 00:08:36 | A river went in the (inaudible), and it dried out. |
| 00:08:40 | Let me tell you where it was, all right? This is in an island- |
| 00:08:47 | Hawaii. |
| 00:08:50 | Does that help? The island of Hawaii. |
| 00:08:52 | Oh. |
| 00:08:53 | Hawaiian islands- |
| 00:08:54 | I got it. |
| 00:08:55 | There's many islands. The biggest one is- is Hawaii. The one that has the- the capital, Oahu- or Honolulu is on the island of Oahu. |
| 00:09:04 | But there's something about the Hawaiian islands. |
| 00:09:08 | Me. |
| 00:09:09 | What is that? What was that? //Jeffrey? |
| 00:09:11 | //They're all volcanoes. |
| 00:09:12 | They're volcanoes. |
| 00:09:13 | That's right. |
| 00:09:14 | You're on a volcano. |
| 00:09:16 | Volcano? |
| 00:09:17 | So I'm standing on a vol- near the top of a volcano. Now, if I'm standing on the top of a volcano, |
| 00:09:29 | Why am I not standing on sedimentary rock? |
| 00:09:38 | Why do I have to be standing on another kind of rock that we're gonna call non-sedimentary at least for the time being? Why? Paola? |
| 00:09:48 | Because the lava was probably (running or so)- |
| 00:09:50 | Can't hear. |
| 00:09:51 | Because it was probably hot, the rock or the lava was running or something. |
| 00:09:56 | Well, you're getting close. |
| 00:09:57 | Moist, or- |
| 00:09:59 | You're getting close. What is it? What do you say, Carl? |
| 00:10:04 | Because of the (inaudible) going into the hole, it could probably break off. |
| 00:10:10 | No. |
| 00:10:12 | Wait a minute. We just got through saying not 10 minutes ago that if sediments get deposited in some sea and they get buried deep enough- |
| 00:10:26 | they may be pressed into sedimentary rock. |
| 00:10:31 | Now, I'm not standing on sediments, and I'm not standing on sedimentary rock. What kind of rock am I standing on? |
| 00:10:41 | Mountain. |
| 00:10:42 | What is that- what do you say there, uh, Kyra- uh- |
| 00:10:48 | Kyra. |
| 00:10:49 | Kyra. |
| 00:10:50 | Kyra. |
| 00:10:51 | You're standing on non-sedimentary rock. |
| 00:10:52 | Yeah, but how is it different than sedimentary rock? Think the way this rock- this rock forms. |
| 00:11:03 | How did it form? |
| 00:11:04 | Because, um- |
| 00:11:05 | How did it form, Terrence? How does it form, Samuel? |
| 00:11:09 | By heat. |
| 00:11:10 | Heat. |
| 00:11:15 | Heat is necessary. Sonia? |
| 00:11:18 | Is it metamorphic rock? |
| 00:11:22 | Magma. |
| 00:11:23 | What comes out of a volcano? |
| 00:11:26 | Lava. |
| 00:11:27 | Okay. //Now, |
| 00:11:28 | //(inaudible) magma. |
| 00:11:29 | we can call it lava if it comes to the surface. |
| 00:11:33 | Some lava never comes to the surface. We can't call it lava; we have to call it magma. |
| 00:11:40 | Once you say magma, you include the magma that comes to the surface that we call lava, |
| 00:11:46 | or magma that never makes it to the surface, stays underground. Now, look at your charts. |
| 00:11:55 | What has to happen to magma, or in other words, molten rock- that's where the heat comes in- in order for it to become solid? Think about it. |
| 00:12:07 | It has to cool. |
| 00:12:08 | That's right. So if magma cools, it becomes solid, much the same way that when water cools it becomes ice. |
| 00:12:20 | And what kind of rock is this non-sedimentary rock? It doesn't come from sediments. What is it, Terrence? |
| 00:12:29 | It's igneous rock. |
| 00:12:31 | Very good. So there's another type of rock. Now, look at this. Let me lower the screen a minute. |
| 00:12:44 | So I- I went down the slope of the volcano, I walked about four or five miles, and I came to this sign. |
| 00:13:07 | So I'm giving away my age. What does it say there? |
| 00:13:15 | September 1974- |
| 00:13:16 | Sheba, what does it say? I know if you can see it, the rest of us can see it. |
| 00:13:19 | "September 1974 Lava Flow." |
| 00:13:22 | Okay. What kind of rock do you think this is? |
| 00:13:28 | Igneous. |
| 00:13:29 | What kind of rock, Antwone? |
| 00:13:31 | Magma. |
| 00:13:32 | Huh? |
| 00:13:33 | Magma. Lava. |
| 00:13:34 | You're right. Lava is magma, but this long since cooled down. This isn't hot anymore. It became solidified. What kind of rock? |
| 00:13:46 | Igneous. |
| 00:13:47 | Okay. So let's put that one on the board. If you had to- if you had to describe how igneous rock is formed, how could you say it in one sentence? |
| 00:14:08 | One sentence. |
| 00:14:15 | One sentence. |
| 00:14:17 | Cold lava. |
| 00:14:18 | What would you say, Terrence? One sentence. |
| 00:14:29 | I don't know. |
| 00:14:32 | It's on the chart right in front of you. |
| 00:14:47 | You see it? |
| 00:14:48 | Yeah. |
| 00:14:49 | All right. How does igneous rock form? |
| 00:14:57 | How does it form, Kyra? |
| 00:15:00 | Igneous rock is formed when magma cools. |
| 00:15:02 | Can't hear. |
| 00:15:03 | Igneous rock is formed when magma cools, (magma). |
| 00:15:14 | Now, when magma cools, what happens to the state of matter that it's in? There's a change in state of matter? |
| 00:15:21 | Yeah. |
| 00:15:22 | Yeah. So what's the change, Rudy? |
| 00:15:23 | Solid. |
| 00:15:24 | From liquid to solid. |
| 00:15:25 | Okay. So it becomes solid so we could say it solidifies. |
| 00:15:34 | There you go. All right. Now, look at this. |
| 00:15:41 | What evidence is there that this is igneous rock? Look at- look at the surface. Look at the surface. |
| 00:15:57 | Look at the surface. |
| 00:16:05 | Touch it. |
| 00:16:06 | How come you don't want to touch it? |
| 00:16:07 | It's not hot anymore. |
| 00:16:13 | All right. Anyone see any evidence? Remember, it was once liquid. |
| 00:16:21 | Oh, oh, oh, I know. |
| 00:16:22 | What do you see there? What do you see, Terrence? |
| 00:16:26 | It's like- the little holes inside of it. |
| 00:16:29 | Well, you're right. What do you think the little holes are from? |
| 00:16:32 | Bubbles. Bubbles. |
| 00:16:34 | What kind of bubbles? |
| 00:16:35 | Magma bubbles or lava bubbles. |
| 00:16:37 | Oxygen. |
| 00:16:38 | Well, what makes bubbles? |
| 00:16:40 | Heat. |
| 00:16:41 | Air. |
| 00:16:42 | Liquid. |
| 00:16:43 | Air. |
| 00:16:44 | Air. Some kind of gas. |
| 00:16:46 | So when this magma came up through the volcano in Hawaii, the magma that it contained had a lot of gas in it. |
| 00:16:58 | I guess it was something like club soda, has bubbles in it. So when the rock cooled and solidified- |
| 00:17:04 | The holes- |
| 00:17:05 | The holes- yeah. The holes became preserved. All right? Now, take a look at your chart. I want to show you something. |
| 00:17:14 | Right under the rock cycle chart is a scheme for igneous rock identification. |
| 00:17:25 | Now, you see where it says vesicular? |
| 00:17:28 | Mm-hm. |
| 00:17:29 | You see? Look where I'm pointing. |
| 00:17:30 | Yeah. |
| 00:17:31 | Vesicular means gas bubbles. So what I'm holding is vesicular basalt, all right? Gas bubbles. You could write it right on your chart. |
| 00:17:45 | All right? Now, I want to show you something else. |
| 00:17:50 | All right. I'm gonna pass back two igneous rocks. In a way they're almost the same, and in another way they're different. |
| 00:18:01 | It's hot. |
| 00:18:02 | Well, that's because it was near the projector. All right. I just want you to look at it and then pass it back. |
| 00:18:08 | You can touch it, but pass it back, because one of these is a fairly rare rock, and I don't have enough for everybody. |
| 00:18:17 | Pass it. |
| 00:18:19 | (inaudible) pass it. |
| 00:18:20 | Okay. I'm gonna give one to Antwone. |
| 00:18:27 | All right. Now, take a look at this. |
| 00:18:31 | Now, I'll tell you up front that you're looking at igneous rock, two different samples. Now, if I- if it's igneous rock, where did it come from? |
| 00:18:47 | Lava. |
| 00:18:48 | Lava. |
| 00:18:49 | All right. Well, yeah. Don't call it mag- don't call it lava. Let's call it magma. |
| 00:18:54 | Magma. |
| 00:18:55 | Okay? |
| 00:18:58 | Now, let me tell you a little story. |
| 00:19:07 | Here's a cross-section of some part of the crust of the earth. Now, what do you think these horizontal layers are? |
| 00:19:20 | Bricks. |
| 00:19:21 | What kind of rock? |
| 00:19:22 | Bricks. |
| 00:19:24 | Limestone. |
| 00:19:25 | What kind of rock? |
| 00:19:26 | Bricks. |
| 00:19:27 | What kind of rock comes in layers? |
| 00:19:29 | Sediments. |
| 00:19:30 | Yeah. All right? So these are different types of sedimentary rock, the layers. Oldest is on the bottom. |
| 00:19:37 | Now, what does it say- what does it say here, Kyra? If you can see it, everybody can. |
| 00:19:44 | Magma source. |
| 00:19:45 | Magma source. |
| 00:19:46 | Okay. So at one time this was molten. What happened to at least some of the magma? Look. |
| 00:19:56 | It went up. |
| 00:19:57 | Well, what happened? What happened, Corey? |
| 00:19:59 | It went up. |
| 00:20:00 | That's right. And what we say is it intruded into the rock that was already there, so we call this an igneous intrusion. |
| 00:20:12 | Sort of intruded into the rock that was already there. Now, let's follow this intrusion. Where did this intrusion wind up? |
| 00:20:23 | On the surface. |
| 00:20:24 | Ah. Okay. Now, that could be a kind of volcano that they have in Hawaii- they're called shield volcanoes- |
| 00:20:32 | because the magma is very liquidy and loose, so it spreads out. |
| 00:20:37 | Now, why would this magma that came out at the surface cool faster than the magma, let's say, that never made it to the surface? |
| 00:20:50 | (inaudible) |
| 00:20:51 | I mean, there's a lot. I'm just using this as an example. Cools slowly. Why? Why is that, Delia? |
| 00:20:59 | Because maybe the air made it cool faster, that's on the surface. |
| 00:21:02 | That's exactly right. As a matter of fact, some magma cools even quicker. There's magma- there are volcanoes under water, |
| 00:21:10 | and the magma comes up and freezes much quicker than it does in the air. But, anyway, how many people have ever made rock candy? |
| 00:21:21 | Me. |
| 00:21:22 | All right. The longer you let that string hang in the water, what about the size of the crystal? Did you make it that way? |
| 00:21:33 | No, never- |
| 00:21:34 | All right. Let me show you something. Magma is a liquid, and in the liquid you have charged atoms. |
| 00:21:44 | In the seventh grade, you learned that atoms when they become charged, when they become dissolved, |
| 00:21:53 | when they became liquid form- when the state of matter changes, they become ions. |
| 00:21:58 | Now, since this is magma and it's a liquid, the atoms can move around. What do you think's gonna be attracted by a positively charged ion? |
| 00:22:09 | //Heat. |
| 00:22:10 | //Elec- |
| 00:22:11 | Heat. |
| 00:22:12 | Huh? |
| 00:22:13 | Electricity. |
| 00:22:14 | Heat. |
| 00:22:16 | Why? |
| 00:22:17 | (inaudible). |
| 00:22:18 | Right. So given enough time, positive atoms- positive ions attract negative ions and negatively charged atoms, and they'll- |
| 00:22:31 | they'll line up due to electrical charges. Given enough time, they arrange themselves very orderly, and you might wind up with something like this. |
| 00:22:49 | That's cute. |
| 00:22:51 | What is it? |
| 00:22:52 | A crystal. |
| 00:22:53 | It's a crystal. |
| 00:22:54 | It's a cry- That's all a crystal is. It's an orderly arrangement of atoms, |
| 00:22:56 | and the atoms align- aligned themselves when the magma was liquid, when it was in a liquid state. |
| 00:23:04 | So the longer the magma stays liquid, what can you say about the size of the crystal? |
| 00:23:10 | It gets bigger. |
| 00:23:11 | It gets bigger. Okay. But suppose the magma comes out at the surface and cools real quick. |
| 00:23:20 | What's gonna happen to the charged atoms? Will they have a chance to line up and become- |
| 00:23:27 | No. |
| 00:23:28 | All right. Now, remember the rocks I passed back. |
| 00:23:34 | There was one that had big crystals, and there was one that had small crystals. Who has the rock now? |
| 00:23:43 | All right. Do me a favor, Shevaun. Hold up the one that you see has big crystals. |
| 00:23:53 | Okay. And how do you know it has big crystals? |
| 00:23:56 | Because it's kind of sparkly (inaudible). |
| 00:24:00 | Yeah. Here it is. Well, here it is. I put this down on my floor. |
| 00:24:05 | Marble. |
| 00:24:06 | No, it's not- you can see //the- |
| 00:24:08 | //Granite. |
| 00:24:09 | That's right. It's granite. |
| 00:24:12 | All right? So this- this, that cooled under ground, the crystals had time to line up, the magma took a long time, |
| 00:24:21 | because it cooled very slowly, so you get large crystals. |
| 00:24:31 | But where the magma- but where the magma comes out at the surface, |
| 00:24:37 | atoms don't- and magma freezes really quickly, atoms don't have time to line up, you get small crystals. |
| 00:24:47 | Okay? Now who else has the rock now? |
| 00:24:50 | Okay, Antigua, hold up the rock that cooled quickly. |
| 00:24:57 | Hold it up. How do you know that cooled quickly? |
| 00:25:00 | Because it doesn't have a lot of crystals. |
| 00:25:03 | Can you see the crystals? |
| 00:25:04 | No. |
| 00:25:05 | Can you see little specks in there? |
| 00:25:09 | Yeah. |
| 00:25:10 | Those may be those tiny crystals, all right? Now, one more thing. If you're wondering how I'm naming these rocks, it's all on the chart. |
| 00:25:22 | First of all, is the rock that you are holding- is it light colored or dark colored? |
| 00:25:31 | Light colored. |
| 00:25:32 | Light colored. Okay. Now, notice on your chart it says color: light. So these rocks over here are all light in color. |
| 00:25:45 | Now, according to the chart, what the- what's the color of these igneous rocks? |
| 00:25:51 | Dark. |
| 00:25:52 | Yeah. It says "dark." So since they're light in color, I know and you should know that it could be granite or rhyolites, |
| 00:26:04 | or even a rock called the pegmatite. Now, look over here where it says grain size. |
| 00:26:14 | That's a way of describing the crystal size. You might want to write "crystals" here. |
| 00:26:23 | All right? Which of these- which of these word- which of these correspond to something that has a fine grain or tiny crystals? Look at the measurements. |
| 00:26:34 | Less than- |
| 00:26:35 | Okay. Less than one millimeter or less than a tenth of a centimeter, light colored. That rock is rhyolites. |
| 00:26:47 | But if it has bigger crystals, let's say a tenth or one millimeter to a centimeter big- |
| 00:26:55 | It's granite. |
| 00:26:56 | That's right. Then it's granite. So it's really very simple. |
| 00:27:03 | Now, if the rock took a real long time to cool, if it's one centimeter or 10 millimeters or larger, then it's called pegmatites. |
| 00:27:19 | Let me see. Here's the pegmatite. Look how big those crystals are. There's one crystal right here. It's feldspar. All right? |
| 00:27:34 | So this one took a real long time to cool. The crystals are really big. We say it has a very big grain size. Okay. Let's wrap this up. |
| 00:27:49 | How do you know by looking at an igneous rock, where the rock cooled? |
| 00:27:54 | Where the magma cooled? What's the general rule, Yolanda? |
| 00:28:00 | Maybe because it has a different type of rock in it. |
| 00:28:04 | Look at the rock. How do you know that the magma that formed an igneous rock cooled underground? How do you know, Rudy? |
| 00:28:13 | Probably because of the size of the crystals. |
| 00:28:14 | Okay. So as the magma cools underground- Rudy, what did you say? |
| 00:28:21 | The size of the crystal. |
| 00:28:23 | Well, tell us about the size. |
| 00:28:25 | //The size- the size of the- |
| 00:28:26 | //Big? Little? |
| 00:28:27 | Big. |
| 00:28:28 | Okay. |
| 00:28:32 | And on the other hand, if the magma came out at the surface maybe through a volcano- |
| 00:28:46 | Smaller. |
| 00:28:47 | Then what's gonna be the size of the crystal? What, Terrence? |
| 00:28:53 | Small. |
| 00:28:54 | Okay. |
| 00:29:01 | All right. Now, listen to this question. Here's another igneous rock. |
| 00:29:16 | You see any crystals in here, Eric? |
| 00:29:18 | No. |
| 00:29:19 | Okay. Tiny crystals. What's the name of this rock? Look at your chart. Look at your chart. |
| 00:29:29 | Here. I got one that was transported by a stream. What's- very ti- well, it's round. |
| 00:29:37 | Oh, my gosh. |
| 00:29:38 | It's really heavy. |
| 00:29:40 | Yeah. |
| 00:29:42 | What's the name of it, Shevaun? |
| 00:29:44 | Basalt. |
| 00:29:45 | Very good. How did you get basalt? |
| 00:29:48 | Since Eric said it was tiny in crystal. |
| 00:29:51 | Okay. |
| 00:29:52 | I looked at "less than one millimeter." |
| 00:29:54 | Very good. |
| 00:29:55 | And I looked at the dark side. |
| 00:29:56 | Ah. (inaudible) dark. Basalt: small, tiny crystals, dark in color, and- look- here are the minerals that make up the rock. |
| 00:30:12 | Here are the minerals that make up granite and rhyolite. |
| 00:30:17 | Why do you think granite and rhyolite are light in color? What does that tell you about the minerals- the color of the minerals that make it up? |
| 00:30:25 | It has to be- |
| 00:30:26 | What? |
| 00:30:27 | It has to be a light color. |
| 00:30:28 | Yeah. And look: quartz, clear to white; feldspar, pink to white. |
| 00:30:36 | So the rock is white- light colored, because the minerals that make up the rock are light. |
| 00:30:43 | But on the other hand, different parts of the world have different magmas. It's like soup. |
| 00:30:51 | So this soup, or this magma, contained dark ones. Here's a dark green. All right? Here's a little bit of black. |
| 00:31:01 | So now you know how to name the igneous rocks. Now, suppose you had an igneous rock that cooled so quickly no crystals had time to form. |
| 00:31:11 | What's the name of that rock? I can't pass this around because it happens to be very, very sharp. |
| 00:31:20 | Ballistic glass. |
| 00:31:22 | That's right. It's glass. |
| 00:31:29 | If you ever wondered how did the cavemen shave- how do you- how do you- how did they shave before they had- |
| 00:31:36 | With rocks. |
| 00:31:37 | With basaltic- |
| 00:31:38 | With rocks. |
| 00:31:39 | This. If you hit it the right way, it flakes off, and you get something as sharp as a razor blade, even sharper than a razor blade, |
| 00:31:49 | and that's how they shaved. |
| 00:31:53 | No, really, //if |
| 00:31:54 | //Was it like that? |
| 00:31:55 | //No. |
| 00:31:56 | //I mean- that's how they shaved, and another thing is, this is- this is one of the items that Indians used as arrowheads and knives. |
| 00:32:03 | Yeah. |
| 00:32:04 | All right? Now, here. How did you know that, Shevaun? |
| 00:32:08 | What? |
| 00:32:10 | Where does it say that? |
| 00:32:12 | Right here- |
| 00:32:13 | It's at the top. |
| 00:32:14 | Okay. |
| 00:32:15 | It's ballistic glass. |
| 00:32:17 | No crystals. No crystals tells you something about how fast the magma cooled. |
| 00:32:24 | It cooled real fast. |
| 00:32:25 | Right. So in this case there's magma that cooled so quickly no ions have time to line up, |
| 00:32:34 | and you get obsidian if it contains these minerals or basaltic glass if it contains the darker ones. |
| 00:32:46 | All right? Now, I sometimes do this. How did- how did the cavemen- |
| 00:32:51 | or how did the American Indians, people that- or before they invented- discovered metal, how did they flake these? |
| 00:33:00 | How do you make a tool out of this? |
| 00:33:02 | Scrape it against another rock. |
| 00:33:03 | No. They didn't do that. |
| 00:33:07 | They didn't do that. And they made some very fine tools out of this. |
| 00:33:15 | I think the Egyptians used this as scalpels. They did operations. So did the Indians in South America. They did operations. |
| 00:33:23 | They didn't have knives- well, they had knives, but how do you fashion this into a sharp-edged tool? How, Sonia? |
| 00:33:31 | They could take it and they (chopped) it on the ground or something. |
| 00:33:40 | Take a (inaudible) the same thing. |
| 00:33:41 | All right. |
| 00:33:42 | I see, you have to take a- |
| 00:33:43 | I'm not gonna do it; I'm afraid it's gonna fly off and hit somebody, but if you hit it just the right way- |
| 00:33:48 | they used their hands and another tool to bang it on. If you hit it just the right way, you get these flakes that are real sharp. |
| 00:34:04 | Mm-hm. |
| 00:34:09 | I think one went into my finger. I feel a little splinter. |
| 00:34:12 | It's right there. |
| 00:34:18 | Clean as a whistle. It's as sharp as any razor blade. |
| 00:34:30 | All right? How many people saw the movie Congo? |
| 00:34:35 | Me. |
| 00:34:36 | Okay. I didn't see it. My son told me about it. It has to do with diamonds, right? |
| 00:34:42 | Yeah. |
| 00:34:43 | All right. Delia, what about the diamonds? Where were they? |
| 00:34:47 | They were in some cave. |
| 00:34:49 | How big were the diamonds? |
| 00:34:53 | I don't remember. |
| 00:34:54 | All right. I read an article just two days ago. They didn't use real diamonds. |
| 00:35:00 | Glass. |
| 00:35:01 | (It was fake?) |
| 00:35:02 | They didn't use glass. |
| 00:35:03 | //Stones. |
| 00:35:04 | //Diamonds? |
| 00:35:05 | They used a mineral that you find in granite. It's the clear one. It's called quartz. |
| 00:35:13 | All right? Now, this crystal of quartz, is kind of rare because it's called the twin. It has a point on both sides. |
| 00:35:31 | Not like this one that has- it's only pointed on one side. Now, as far as I know, there's only one place that has these quartz. |
| 00:35:41 | It's called Her- it's found in the city of Herkimer, New York, and they call it a Herkimer diamond. |
| 00:35:49 | It's not really a diamond, but it has this shape like a diamond, and that's what they used as diamonds in the movie Congo. |
| 00:35:59 | All right? Now, I told you- we talked about Cooperstown- Cooperstown, New York. |
| 00:36:08 | Remember Cooperstown? Remember Howe Caverns? |
| 00:36:13 | Yeah. |
| 00:36:14 | Right, Howe Caverns? |
| 00:36:15 | Well, if you go into Howe Caverns to see the limestone cave- |
| 00:36:27 | All right? Right here. I think it's a little north of Albany. |
| 00:36:34 | If you go a little further north- remember the Baseball Hall of Fame is here- you have the town of Herkimer |
| 00:36:43 | and as soon as you get into the town of Herkimer you see signs, "Visit the Herkimer Diamond Mines," and that's where it is. |
| 00:36:50 | You go to the Herkimer Diamond Mines. They rent you- Antwone, you looking for it? |
| 00:36:56 | Yeah. |
| 00:36:57 | You see it? You can rent hammers, goggles, and they'll send you out into this cliff, and you can hack away at the rock, |
| 00:37:10 | and that's how I found the- this Herkimer diamond. They're there for you- they're there for you to get. |
| 00:37:17 | (inaudible) |
| 00:37:18 | Yeah. So it's- it's kind of a neat geology- neat geology trip to go to Howe Caverns, go a little further north, and find- mine Herkimer diamonds. |
| 00:37:32 | They're very- I don't think they're found anywhere around the earth except in Herkimer, New York. |
| 00:37:40 | All right, now let me ask you- here's a tough question. |
| 00:37:57 | Okay. How many people saw ET? Does that look familiar? |
| 00:38:03 | No. |
| 00:38:04 | That look //familiar? |
| 00:38:05 | //Yes. |
| 00:38:06 | No. |
| 00:38:07 | This is in Yosemite National Park. It's called Devil's Tower. I believe it's in Yosemite. It's out west. Now, this is solid granite. |
| 00:38:20 | How could you explain- since granite cools underground slowly- that's why it has big crystals- |
| 00:38:27 | how in the world can this piece of granite be above the surface? |
| 00:38:42 | What do you think, Paola? |
| 00:38:47 | Oh, um- |
| 00:38:49 | All right. This has large crystals. It cooled slowly, it cooled underground, but yet here it is. |
| 00:39:03 | What do you say, Eric? |
| 00:39:05 | I don't know. |
| 00:39:06 | What do you say, Carl? |
| 00:39:07 | Huh? |
| 00:39:09 | What do you say, Corey? |
| 00:39:13 | I don't know. |
| 00:39:14 | Kyra? |
| 00:39:15 | There is probably more (than one layer of it). |
| 00:39:16 | No. Samuel? |
| 00:39:18 | Maybe- since it's underground, maybe it was pushing up on the surface, and the surface just probably cracked, and it just came up. |
| 00:39:26 | Oh. You mean- what are you saying? It really did cool underground? |
| 00:39:30 | Yeah. |
| 00:39:31 | All right. So if it cooled underground, that would account for the large crystals. |
| 00:39:41 | But you see it now above ground- so what do you say, Yolanda? |
| 00:39:47 | Maybe it cracked the ground, and it came- and it just kept rising. |
| 00:39:52 | So you mean something pushed it up? |
| 00:39:55 | Yeah. |
| 00:39:56 | Okay. That's very good. |
| 00:40:01 | Almost. |
| 00:40:04 | It was pushed up, but at one time it was an intrusion, and there was rock around it. |
| 00:40:17 | And it broke off. |
| 00:40:19 | What happened to the rock around it? |
| 00:40:22 | Or what could have happened to the rock around it? And think back to Niagara Falls. |
| 00:40:30 | Carl? |
| 00:40:31 | Because (inaudible). |
| 00:40:34 | Water went over it, and it pushed up. |
| 00:40:37 | It might have been water, what? |
| 00:40:39 | The thing that rubbed against it. |
| 00:40:41 | What wore away? |
| 00:40:42 | The rock. |
| 00:40:43 | The rock. |
| 00:40:44 | The s- why? |
| 00:40:45 | Because they were soft. |
| 00:40:46 | Very good. It must have been softer. Okay. |
| 00:40:50 | That was a good lesson. |
| 00:40:51 | Thank you. Yeah. All right. |