Geoscience Education in the Mountain State:
CATS Geology Telecourse, Spring 1999,
Show 2 Transcript

CATS Telecourse Broadcast
Historical Geology
January 20, 1999

Dr. Bob: Greetings! Here we are again, show number two, with Deb Hemler, Bob Behling, Tom Repine, and many others are back in the room with all the technology. We're going to talk about life and diversity and pull together some of general things from physical geology talked about last semester. We'll also talk about geologic time. Before we begin that though, I'd like to mention a few things about the syllabus.

First of all, there will be six live broadcasts. This is the second. We will have one in February, one in March, and then two in April. Our last show will be April 28th. The course itself will use geologic time, from oldest to youngest events, as our organizational structure. As we often do, it we start from the bottom and work up. So we'll be in old time at the beginning of each broadcast.

We'll talk a little bit about what we did the last time. So, Deb, could you fill us in? What did we attempt to put together in show number one?

Deb: What we were trying to do was to take a quick look at what we did last semester in physical geology and show how that ties into historical geology. What I'm going to do now is a detailed review for those of you that missed last week and those of you that had problems with the audio.

What we'll be talking about this semester is historical geology. We'll take a look at the rocks in West Virginia and determine the history of those rocks. If you look at the rock column that I've drawn, you can tell a lot about what happened in West Virginia relative to the rock types that are found there. So, every time you're traveling down the highway and you see exposed rocks, we want you to look at it and think about what history or what events or what types of environments were there to put that rock there. So if we can do that for you by the end of the semester, then we've done our jobs. We're trying to tell a story. That story then comes from the rocks that are exposed in West Virginia, some that aren't exposed. So our story then, primarily in West Virginia, is going to be one about sedimentary rocks. If you were with us last semester, we talked about sedimentary rocks in great detail and how they were formed. But just quickly, we're talking about rock fragments from other rocks that have been cemented or compacted together--deposited somewhere, cemented, and then lithified into a rock.

Dr. Bob mentioned a term last week that you may or may not have gotten, and that term was facies. What he was referring to there then is that it's a description of a rock unit. It's all deposited under the same environment, and so that facies then becomes very important about how that rock began or where it came from. So we'll talk a lot about facies. Each deposition then is a different facies.

Then he also mentioned another term and that was the basement rock. Dr. Bob likes to refer to the basement rock and refer to that as deep time, as you just heard him refer to it. You can tell why it's considered deep time because it's at the bottom. It's below a lot of strata and therefore we've got to study what's above it to determine what buried that basement rock.

Let's consider two things that we already talked about. We talked about the principle of uniformatarianism, last time. What that simply means is the present is the key to past. If you're looking at a rock unit and you want to know how it got there, you take a look at the processes that are going on today. In other words, if you have a sandstone, that sediment was originally sand. What today put sand down? We can take a look at a river bar. We can take a look at a beach. We might take a look at sand dune. There are a variety of present-day environments that deposit sand. So if those forces are at work today, they were also at work in the past. So that's what geologists use as their mantra. They look at today's forces and they apply them to the rocks of the past.

Another important concept is the law of superposition. That simply indicates that the stuff on the bottom is the oldest. The stuff on the top is the youngest. If the rocks have not been deformed and moved drastically, that they have been laid down in horizontal layers. But, as sediments get piled one on top of the other, then we realize that the material on the bottom is older than, say, the rock unit on top.

Another thing that we talked about last time was dating. First, there is relative dating. That's based on the law of superposition and that simply says that we can take a look at rock units and determine whether they're older or younger than other rock units. So if we can see rock layer B below layer C, we know that rock layer B is older then rock layer C, simply because rock layer B lies below C. So based on the law of superposition, then, we can now date "relatively" how old things are.

Dr. Bob: The only caveat we have to place on that is that the rocks haven't been thrown up and over, tipped upside down. There hasn't been a big mountain building episode.

Deb: Right. You have to make sure that the rocks are in their original position and that they haven't been deformed.

Dr. Bob: And what's my favorite question in the field? Which way is up?

Deb: On the flip side, we have something that is a bit more specific. That's called absolute dating. We apply a specific time in years and we tend to use different methods for acquiring absolute dating. In this particular rock unit, we have absolute dated it 450-million years old by using a volcanic ash layer.

Dr. Bob: You can find it. It is in West Virginia. There's one in a quarry. It doesn't look like volcanic ash that you might find on the flanks of Mount St. Helens. It has been altered because it was in the sea water. The minerals are now greenish in color and there's just a hint of green discoloration in the sequence of rocks here shown in a brick-like pattern, and that's the remnants of the volcanic ash.

Deb: It's extremely thin. You think of a volcanic ash layer and you think of something huge. But when you actually see this layer, it's just so small, it's almost nondescript. It's amazing anyone found it.

Dr. Bob: In this particular case, the absolute dating is done by looking at potassium argon.

Deb: Let's put the pine cone up there and kind of relate this absolute dating to something that maybe the kids and everybody is familiar with first. This is a pine cone that happened to have been shipped to me from Aimee Govett from Las Vegas. This happens to be from a bristle-cone pine. If I wanted to determine how old the tree was that this cone was removed from, I could ask a dendrologist to core the tree. He'd pull the core out and count the annular rings to determine the age of that tree. So that's an absolute date. Kids know that they can age a tree by counting its annular rings. You can also do this with fish and fish scales. There are quite a few things that you can count annular rings and get an absolute date on. So we can get a bristle-cone pine tree's absolute date. Scientists have actually done this and bristle-cone pines can actually be aged upwards of 8,000 years old. So this particular bristle cone wasn't that age, but they have found bristle-cone pine trees to be 8,000 years old. So that's the absolute date on that bristle-cone pine tree. That's going to play importantly here in a minute. But that's an example of absolute dating. And that's what a dendrologist might use. Geologists, on the other hand, do what Dr. Bob was referring to earlier and that is they use radiometric dating or isotopes.

Dr. Bob: Well, this one is interesting with the bristle-cone pine because the diameter of the tree, it isn't as huge as a sequoia or a redwood.

Deb: Right, it's not. It's kind of small and knarled.

Dr. Bob: It's kind of small and knarled, so you can imagine that it takes essentially microscopic work to start counting these layers.

Deb: It's not as easy as it looks.

Dr. Bob: You can also tell which are good years and which are lean years from the standpoint of the growth of the tree. A wet year with good maximum conditions, you get a good thick layer. A drought condition, as we have seen in West Virginia over this past summer, will probably translate into a relatively thin weak layer. But it will be there, it will be distinct.

Deb: Actually, you can determine by the layer itself how long the wet season was as opposed to the dry season because there is a discoloration in the annular rings. You can tell a lot about trees and tree dating.

Let's take a look at what geologists use for absolute dating. They use radiometric dating, not tree rings, but they work sort of in the same way in that they can get an absolute date on a rock unit. If something is relatively young, say less then 70,000 years, they can use carbon-14 dating. In carbon-14, what they do in radiometric dating is to simply take the half-life and figure out the ratio of what an isotope turns into. It's daughter isotope and they compare the daughter isotope with the parent isotope to determine how many half-lives this thing has undergone, how many decays it has undergone. So if something is relatively young, we use carbon-14. Something, say, intermediate we might use uranium-234. This is incorporated into corals and reefs, and uranium-234 can be used for anything younger then 300,000 years old. That's how they might age a reef, for example.

Something older, that you were getting at earlier, is the potassium argon dating. That's what they're using to date ash layers or igneous rocks. And then there are other ones.

Dr. Bob: The carbon is essentially the organic material. The other units, let's just list them here. There's carbon-14, potassium argon, uranium lead, and this U-234 is one isotope, and rubidium strontium. Those are the main four.

Deb: So what scientists have done, then, is they've taken this radiometric dating and they've actually taken moon rocks and they've determined the age of the moon. And assuming that the moon and the earth are about the same age, they've determined that the earth is 4.6-billion years old. So the question is, is it 4.6-billion years old? Originally, we thought that the earth was 4,004 years old based on estimate done by Bishop Usher. As a matter of fact, he traced the biblical lineage and determined that it was actually created on October 26th at 9 am in the morning, 4,004 years ago.

Well, the big question then is, if a bristle-cone pine is 8,000 years old, how can the earth be 4,004 years old? We sort of have another principle at work here that we use in geology and that is that you can't have something older or younger then the oldest plant found living on the earth's surface. So this 4.6-billion years old is based on radiometric dating or absolute dating and radioactive isotope decay.

Dr. Bob: But, the oldest rock we've ever been able to find on earth has yielded a date of 3.98-billion years BP (before present), and present turns out to be 1950. It was used as a convention. By convention, we used 1950 as a time when we were developing all these techniques. So the oldest rocks we find are not the expression of the age of the geologic earth. The old ones are lost. These type of rocks we find are rocks that have been altered or changed dramatically by earth processes. Therefore they must have been around for a long time in order to be changed.

Deb: So to bring us up to today, the last thing we really talked about, and this is the earth at 4.6-billion years old. The 4.6-billion years is not represented on what we call the geologic time scale. You have a copy of that geologic time scale that your facilitator gave you. It's yellow. This is how we represent the history of the earth in geologic time. And as our tradition, the oldest appears at the bottom and the youngest appears at the top. We just simply went over that last week and we mentioned that there were three eras that we focus on. Paleozoic, meaning old, the oldest. We'll spend a lot of time on the Paleozoic in West Virginia. Mesozoic, being middle. The age of the dinosaurs. And then the Cenozoic, or recent, being the age of the mammals. In West Virginia, you'll see that there's nothing above the Paleozoic except some Cenozoic or Quaternary rocks that are kind of deposited on the top in the form of river deposits. You'll see a lot of yellow on geologic maps and those are when the rivers have placed rocks that are being deposited.

Dr. Bob: Why is it missing? Was it ever here? Or if it was once here, do rivers and other processes have the potential sweeping the evidence away? Also, you have many ways of expressing this. There's another form and this you also have a copy of, and this will be found in your book. The colors are pastel, they don't copy real well on the overhead but this type of diagram helps you place into perspective some of the critical changes and life forms. Now be aware of the fact that life forms go back into deep time, but we're not talking about life forms with hard parts. We're not talking about very complex multicellular forms. We'll get to that eventually. Historical geology is in great measure talking about fossils and life on earth. But it's also talking about processes and events on earth. Well, that finishes that component.

Deb: I think that brings us up to this week's show.

Dr. Bob: Up to speed in this week's show. We will not have to spend as much time on review perhaps in weeks to come. But we will do that to insure that you remember what we've been talking about and where we are as we head forward. And as we get into shows four, five, and six, the linkage will be the events, life forms, and geologic eras that we talked about.

And now we are turning a page. And those pages are literally periods of the Paleozoic, time divisions that are significant in absolute. We are talking in terms of maybe 100-million years or so. But we turn those pages of time literally and figuratively to watch the development on earth and specifically what was happening here in our state of West Virginia.

Well, an additional factor that we must engage in is to be sure that we have a general understanding of rock types. Igneous rocks are born of fire. That's how the word was derived. And igneous rocks can cool in one of two broad locations external to the earth's surface--that is, on the earth's surface or internal. So there's two possibilities. If it comes out external, then it cools rapidly. If it's internal and never sees the light of day until erosion a long, long time later, it cools slowly. The cooling rate dictates the grain size because as the molten material-- and all molten material is magma--as that material cools, the crystals form. The individual atoms of elements that are present in the magma, in the cauldron if you will, are going to come together to form minerals. Given sufficient time, it starts to become a sluggish mass, more like the consistency of toothpaste. And the ions migrate through this and seed crystals then grow. You have perhaps in your classroom have shown students how crystals can grow. Perhaps you used a very simple solution, a sugar solution, and then put in a string and watch rock candy form as the water evaporates from the saturated solution. The crystals form because the sugar is crystallizing out and the water is evaporating and what's left are sugar crystals on a string. No liquid environment at all. Well, in the aqueous environment of the magma chamber, some of the water is driven off as steam. Other components of the water may become incorporated in certain minerals, but by and large this magma is going to cool, and if it cools slowly, it's coarse grained, and if it cools rapidly, it's fine grained. Internal and external.

In West Virginia, there is but a very, very small portion of igneous exposed at the surface. A few places you have to dig to find it. As last week we mentioned, you might go down into Cass Cave and find an exposure of some igneous rock that had worked its way up in very recent geologic time into the rocks in Cass Cave.

The next rock type is metamorphic. Metamorphic have undergone change. As you work in the sequence and learning skills we try to emphasize in CATS is age development. If you work with young kids in K-3, metamorphism is an extremely difficult concept. By the time fourth graders come along, they have a better appreciation perhaps of how change can come about by pressure or temperature. And there are additional components that water under pressure and at high elevated temperatures circulating through rocks can also bring about change. Metamorphism is something that they can understand from the cocoon to the butterfly. That is where the word--that's a change and the word is drawn from the same root. Latin--to change or alter.

West Virginia does not have many metamorphic rocks. We would have to go all the way to the eastern panhandle. And why we have to go all the way to the eastern panhandle to find metamorphic rocks exposed at the surface? We'll discuss this as we go through the semester. It turns out that you'll find metamorphic rocks only at Harpers Ferry. If you're familiar with the geography--and I'd urge you to bring a road map to class, put it in with your package of learning materials in the context of this course because I will talk about towns and locations and counties and you will want to locate that.

The third type of rock is sedimentary. Sediment is the loose material. The rock is known as a sedimentary rock. What happens is loose pieces of material have come about by biologic or chemical means. By chemical I mean precipitation. These chemical precipitates or loose pieces of biochemical precipitates become cemented or squeezed and the result is lithification: made into rock. And that's what sedimentary rocks are.

Over the vast majority of all the state of West Virginia, the rocks at the surface are sedimentary rocks. There are certain components of the sedimentary, certain types of sedimentary rocks that you need to know about, and the initials we use to refer to them. Ss is short for sandstone. Sh equals shale. St or silt for siltstone. For some we hardly ever use abbreviations. For example, mudstone and claystone. These are just some of the sedimentary types of rock. We are naming rock types now because there are so many sedimentary rocks in West Virginia. So there's a whole other suite.

Now the ones that I mentioned are those pieces that have been carried by the wind, or by water, and moved about by water. Then the others, the biochemical rocks, are such that they include coal which is organic material accumulated. For limestone we will use the abbreviation Ls. For coal I usually just write it out. You will see later on that we will reintroduce the symbols to these different types of rocks. You saw some of the symbols on what Deb had put together to review last week's show. We going to reemphasize those again. There are some additional materials that once were in West Virginia and now you can't see them anymore but there is evidence of there once having been here. Rock salt for example. And the emphasis is on rock. It is salt. It was formed in this case by chemical processes, especially evaporation. In the sea, normal saltwater became trapped, it evaporated under the very warm temperatures at the time. West Virginia was very close to the equator at that time. It was warm, much warmer then it is today when we are at more northerly latitudes. So the marine water in an enclosed base evaporated and the dissolved load precipitated out. That's what I meant by precipitation. Sometimes precipitation is in the form of calcium carbonate, a mineral, and I'll talk about that in a moment. We often talk to our students about minerals first and then rocks but what you see first are rocks. That's what kids know about. They see the rocks and we introduce to them the fact that rocks are made up of parts and those parts we call minerals.

So we really do things kind of backwards in an introductory sort of way. We have coal, limestone. There are additional rock types but they're not as common, certainly not in West Virginia. Of the clastic material we introduced this last week. Clastic meant particles, and there's a certain size range. The term clay size is very small. It's less than 1/256 millimeter in diameter--small. The next grain size range is silt size. The coarsest size particle, if it were a perfect sphere, would be 1/16 millimeter in diameter. Then sand size and the largest sand size, by convention to geologists, is two millimeters in diameter. It turns out that geologists, engineers, and soil scientists all use these terms, but they set the breaks and particle size just a little bit different sometimes. And then there are coarser materials. Perhaps the term granule, or pebble, or boulder. Terms that kids have an idea about in relative size. To geologists, the sizes do have meaning and precise dimensions. But seldom are those particles round. In reality, seldom are these particles perfectly round. It's an unlikely situation but we assume them to be.

There is an additional clastic rock that has a component of these coarser pieces to it. In West Virginia, we can find some where there are pebbles in a sandstone, and that material has as a name: conglomerate. That also should be added to your list of sedimentary rocks. It fits, of course, with the clastic ones, the ones I introduced first. It is just not very abundant. When you see it, it's unmistakable. If any of you have been to Bear Rocks at Dolly Sods area, there are quartz pebbles at Bear Rocks, quartz being a type of component of the rock, and they're whitish. Or if you had been at the highest point in West Virginia, you've seen the same thing, that there are those pebbles in it and they are what we call a conglomerate.

Now we're going to explore environments a little bit later. The other aspect of earth materials that we want to insure an awareness of is minerals, the components of which rocks are made. There are literally on earth over 2,000 minerals. There's only about a dozen that we need to know for a practical understanding of geology. There's less then that, that I want to introduce right now.

For example, one mineral that you need to know is a combination of calcium, carbon, and oxygen. And more importantly, the carbon and oxygen are combined to form this family of minerals: carbonates. The carbonates are specific types. There are other carbonates, indeed some other ones found in West Virginia, but the majority are either the calcium carbonate or a combination of calcium and magnesium carbonate. And I put the calcium and magnesium in parentheses to indicate that it's a fifty-fifty split, as the atoms of different elements arrange themselves in space in a very precise arrangement we call a crystal. Half of the locations are occupied by calcium and half of the locations are occupied by magnesium. This implies that these are two different minerals but they're both carbonate minerals.

Then, another important mineral has as its simplest combination simply silicon and oxygen. The mineral name here is quartz. This is a whole new family of minerals: the silicates. Very, very important family of minerals. Silicates have as their diagnostic composition a combination of silicon and oxygen, but they may also have as a family, quite often there's aluminum and hydroxide, which is OH and some other cations. And I'll call them all X: iron, magnesium, potassium, sodium, calcium--common cations on earth. These are the silicates. For completeness and to be in parallel, quartz is the name of this mineral. The mineral that I wrote calcium carbonate is the mineral calcite. This mineral, calcium magnesium carbonate, is the mineral name dolomite.

Then the last critical mineral family that I want to introduce is the fact that iron combines with oxygen and sometimes hydroxide. This mineral is sometimes referred to by its colloquial term, rust. It has a mineral name, it's goethite. It's named after the German author, scientist, woodcarver, and poet Goethe, because he was very interested in minerals. Another form of iron and oxygen is Fe₂O₃. This is hematite. We have some hematite deposits in West Virginia. This mineral, hematite, is very important worldwide as we'll come to find because it can be mined and the iron removed economically to produce iron, and then in combinations with other metals, steel. Very important component. There are many other minerals and the family of silicates are the really critical ones.

I did mention one other rock type and I suppose I better put this additional mineral down because of it. That other mineral is halite. I suspect that if you haven't already had your ration of halite today you will at sometime before you retire this evening. The chemical combination of the mineral halite is simple: sodium and chlorine. We know it by its common term, salt. Recall that I talked about the chemical rock type, rock salt.

So that looking at these minerals, there's an assemblage of minerals and sometimes--I'll abbreviate minerals, "min," and I'll abbreviate "rx"--sometimes the rock is made up of pretty much one mineral for the vast majority of all particles, so that the mineral could be calcite and the rock is limestone. The mineral might be quartz and it has sand-sized grains and the rock is, no great surprise, sandstone. Now you don't find it in West Virginia but it is entirely possible that limestone could form--wave action could rip it up and break it into small particles and the small particles could be redeposited. Or a river might work on a limestone and erode it. It's an old limestone and the river these days is sweeping past and breaking up the particles. It is entirely possible that a sandstone could be made up of calcite particles. It could happen. But in West Virginia, the vast majority of sandstone is dominated by quartz. And to be safe, in West Virginia now, it's sandstone and other silicates, a significant array of silica minerals. Those silicate minerals are very important.

Let me do one other correlation because it will be exceptionally important in West Virginia, that not only can we talk about the clastic particles relating to the mineral component but we can talk about the sedimentary rock being altered to form a metamorphic rock. For example limestone. Its metamorphic equivalent is marble. Siltstone or shale, and shale is a sedimentary rock that shows layers. It's not massive, it looks like many thin sheets put together. But if metamorphosed, shale first could be slate and then if slate is metamorphosed, we have another name: phyllite. So a metamorphic rock can be metamorphosed! And phyllite is in West Virginia. Slate is in Pennsylvania and Vermont. But in West Virginia, whatever we had as slate continued to metamorphose and probably continuously. There never was a time, I don't believe, where we had slate for millions and millions and millions of years and then another event came along. It was just a long continual event and it went all the way to phyllite. In comparing and contrasting now, phyllite has a greater grain size. In general, the rule of thumb is the more pressure and temperature applied over longer periods of time, and perhaps those who teach chemistry already recognize this, the grain size increases. Small grains disappear and their contents are used to enhance or enlarge the larger grains. So large grows at the expense of small. One of the very interesting components, and we don't see this as a rock year-round in West Virginia, but ice is a rock.

Deb: I thought it was a mineral.

Dr. Bob: The ice, you see, could incorporate a lot of other particles into it. Dust particles. So if it's pure water, the ice is thought of as the ice crystals. Pure limestone are calcite crystals. So we're using, interchangeably, an appropriate question, Deb. Interchangeably, this concept of minerals and rocks is confusing.

Deb: It's confusing. Rock salt versus halite.

Dr. Bob: Halite is a term that is not generally well known. That's the mineral name, the precise mineral name to a geologist. Rock salt is something we've used bushels and bags of and tons of across West Virginia to try to cut some of the ice in these recent storms.

Deb: It's always a common question--how do you know it's not the mineral and it is the rock?

Dr. Bob: That's right. We will be here to explain that in greater detail. Ice can be a rock in a glacier, and other particles have blown off the adjacent walls, and that ice is really a rock. A glacier can be looked at like a metamorphic rock and you'd say, whoa, wait a minute. You just said it had to be heat. A lot of pressure will accomplish what heat and pressure together can do. The crystals in the glacier are very big. The ice crystals or flakes were very small.

Before we get carried away, let's take a ten-minute break. We'll come back and get into some more aspects of the geology in West Virginia.

(BREAK)

Dr. Bob: Greetings! Welcome again, we're back. I want to start this portion of the show with a suggestion to you that if you have time to do so, there is an excellent show television show forthcoming. They've shown it once already this week and we're working with the Discovery Channel to get copies. The show is called The Extinction Files. It shows this Saturday, the 23rd, at 6 o'clock. If you look at a schedule, it'll probably be repeated again several hours later or maybe later at night or very early in the morning. It's a really neat show. We'll be telling you about these shows whenever we're on air. We'll try to get rights for all of those that will be valuable to you.

One thing that is always available is the audio bridge. Folks calling in--it tries to give us this real-time opportunity to share and explain if we went too fast, and back up and explain. So we're going to back up. I use several terms, Deb, and what were those terms again?

Deb: You started talking about rock fragments and bio and chemical rocks, and then you threw clastic in there.

Dr. Bob: OK. Clastic, by definition, refers to particles or fragments. They have shape. Sometimes they're angular, but as water works on them, as they travel great distances, they become subrounded, maybe even rounded. It will vary. Examples of clastic rocks are conglomerate, sandstone, shale, siltstone, and claystone or mudstone. Those rocks are clastic.

We can compare and contrast them with nonclastic rocks. Nonclastic rocks are what I introduced as biochemical. Examples would be coal, limestone, and dolomite. I think I introduced dolomite as one of the carbonates. Much of the rock that we see in West Virginia is limestone, a chemical rock. But occasionally we see many of the biochemical components that can make up a limestone, such as shells or fossils in the limestone.

Deb: So then, by your definition, halite or rock salt actually would then be a nonclastic rock.

Dr. Bob: Right. Let's put that down too. We don't see that at the surface in West Virginia. When we drill, we do not find the rock itself. The rock is dissolved. So we find brine at depth. We mentioned last week that's how oil and gas was first discovered. They were looking for salt. Why were they looking for salt in the 1800s? Because they didn't have refrigerators. Always look for connections. The connections were that salt was very important because it preserved food. It removed the moisture. It's really neat. There was also a recent TV series on mummification. How did those in Egypt mummify bodies? They packed it in different chemical compositions but essentially salt to dehydrate the body. That's how they mummified it. They took the water out. If you think about it, what are our bodies mostly anyway? Water.

Now we say all this as clastic and nonclastic but nature can sometimes put in a twist because there's the possibility that river or wave action could break down limestone pieces that were originally chemically created, and create little chunks so there could be a clastic limestone possible also. There's one place just outside of Keyser, West Virginia, a real thin layer where a storm must have ripped off the carbonate mud. Carbonate mud probably deposited in an environment similar to the Bahamas or the Florida Keys. It rolled that mud around, and the mud was still in a plastic sticky fashion and then it solidified. It's really a clastic limestone based on ripping up a chemical limestone. So it can happen. Nature can do these little twists. We'll move with it.

I had promised you a discussion of rock types and symbols. There is a sheet with all these little squares in your packet of handouts. It's titled Appendix 5. There's only a few of these that we need to memorize.

Number 2 (goes to overhead)--I will call these out and sketch again as to how we do these. So number 2 is very useful. The way we do that is we show kind of rounded and smoothed rocks and then little dots. The dots reflect the sand-size grains and the rounded rocks are the pebbles or the conglomerate.

Then, let's say 4, a massive sandstone, it's just the random dots. I'm going to go to the essential ones first and then the variations on the theme.

The next one is number 10, siltstone. The way we do siltstone are some short horizontal dashes with little dots.

Then the next one is number 11, mudstone or claystone, without the other particle sizes that are coarser, and we use just dashes.

The next important one is number 16, limestone. In detail the limestone looks like a brick wall. As a matter of fact, I bet quite a number of you out there, many of you out there teach in a room that has block walls. It's the limestone pattern. You can have all kinds of fun with that in the classroom. That's the limestone pattern.

Another of the rock types that you probably should know, number 27, salt. The salt is usually a very fine, thin pattern of this cross-hatched pattern. In this case, it looks like a plaid. That's often taken as salt.

Then a variation on this, number 18, if we put diagonals, that's dolomite. In the eastern panhandle of West Virginia, we see a good deal of dolomite.

Then there are other variations on these themes. For example, a combination of 2 and 16, we find this in West Virginia that there are sand grains cemented with calcite. So it can either be a carbonaceous or calcareous sandstone or a sandy limestone depending on which of those two blocks dominates. So in this particular case it could be number 5, a calcareous sandstone.

Then there are just a couple others that we need to be aware of and the ones that I use quite often are going to be number 34. A symbol where it's an igneous rock and it's very massive. We sometimes use that or I also use a symbol of little random direction of "V"s as a granitic rock. These are both igneous rocks.

Sometimes for metamorphic rocks, the easiest way to describe metamorphic rocks because they've been put under a great deal of pressure, it's wavy, wavy lines, to show deformation.

That's a nice package, under a dozen. You will come to see these time and again throughout the semester.

Throughout all of geologic time, we are going to be very interested in a component of structure and deformation and massive change on the face of the earth. Our terminology for that is plate tectonics. It has been so discussed on television specials and science books. The plates are rigid plates on the earth's surface, a very limited number. Tectonics you can think of as mountain building. In other words, forces applied. In the context of plate tectonics, there are ways in which the plates can come together. We talk about the plates either as being oceanic, meaning that's its primarily the rock on the sea floor and then the sediments on top of it, or I'll use the letter "c" for continental. Oceanic is real dense. Continental is not quite as dense. The rocks we'd see in West Virginia are the continental rocks.

But if we traveled all the way to Frostburg, Maryland, if rode on I-68 to get to Frederick, Maryland, just before you got off of I-68 onto Route 40 at Frederick, especially on a rainy day, you'll see dark gray-green rocks. They're kind of ugly, but they are gray-green. Of course, what would geologists call green colored rocks? Greenstone, that's it. Those greenstone rocks are metamorphic rocks. They originally were the oceanic floor and they got squeezed together. Now they are exposed to erosion. They're kind of old rocks. They're about a billion years old. It's older times, not really deep time, but it's the oldest rocks that you see around that area close to the tip of West Virginia. We don't have any of those exposed in West Virginia, but they're real close. There are other rocks in that region that are older then the greenstone, but the greenstone are some of these old sea-floor sediments.

Deb: So on a plate, then, you can have both ocean crust and continental crust?

Dr. Bob: That's right. That sometimes is lost in the fine tuning of this. Some plates are very, very large. The North American plate contains most of North America and half of the floor of the Atlantic Ocean to about the middle. Other plates are very small. Many of those small plates are usually simply just oceanic fragments. Then what happens to these plates? They collide. There are forces applied.

There are only three ways in which they can move one adjacent to the other. One possible way the plates can collide is to come together. It's called convergent. No great surprise. Another way is to pull apart, divergent. The third way is to slip side by side. This is a jargon term in geology, transform fault: fault because the rocks are broken; transform because it changes or alters that boundary. All three can be active. The plates, while they are moving, do so at a very slow rate. You can ask your students to look at their thumbnail. If they let that thumbnail grow during the year without breaking it, cutting, or smoothing it off, how far would that thumbnail grow out? Normally fingernails grow at a rate of about an inch per year, about 2.5 to 3 centimeters. That's how fast many of the plates move. Some plates move far less. Very rarely are there more rapid moving plates. In some places plates move up to nine centimeters per year. That's pretty significant. On the island of Taiwan, which happens to be a location in part where the movement is very rapid, they have to after a certain number of years rebuild roads because the roads have deformed or rocks and boulders have moved in response to this very rapid plate action. They have to be recut, and that's really an interesting component. For the most case, it's about the rate that your fingernail is growing. That's a neat little composite. When you get your textbook, there'll be a whole chapter to cover on this, but I just want to do one more thing on the overhead.

Let us revisit the three boundaries. Convergent--the arrows are coming together. There's three possibilities. An ocean plate and an ocean plate are colliding. When that happens, one of these plates goes down beneath the other. The cartoon shows an ocean plate and an ocean plate colliding. One dives down. This is still a convergent boundary, and the water surfaces up here some place. What happens is when this goes down, it's called subduction. I'll write it at an angle to emphasize the motion. That's a jargon word but you can see in the root, "sub," meaning below. One of these yields and goes under. When it goes under it gets warmed. When it gets warmed it starts to melt. As a result, there is a chain or island arc of volcanoes. That's the typical event of an ocean-ocean collision. Where would you find an island arc in one of the 50 states of the United States, where the islands are curved and it's all in the ocean? The Aleutians, an excellent example. The Phillippines are another excellent island arc system. Convergent ocean-ocean.

Is there a possibility where continent and continent collide? Yes, in this case when continent and continent collide, the continental rock is less dense. In some cases we suspect that some of the continent may have subducted, too. The result is that the rock bulges up. What do you get when continent and continent come together? You find the highest mountains in the world. Where would you go to see these? The Himalayas.

Can an ocean and a continental plate come together? The answer is yes. That's the last possible combination and it does in fact happen. In this case, one plate is definitely more dense than the other and will be subjected in the cartoon to subduction. The oceanic plate goes down, the continental plate bows or bulges. There is melting rock rising to the surface, in this case not to form an arc of islands, but rather on the edge of the continent volcano masses. Are there volcanoes from California through Oregon, Washington, and up into British Columbia? Sure are. That volcanic cone area is not a straight line. It goes from Lasson Peak in California all the up to include Crater Lake, Mt. Rainier, Mount St. Helens, Mt. Hood, Mt. Baker. Mt. Baker's up further to the north. A sequence we call the Cascades. There's another example in South America and there it's the Andes. The Andes and the Cascades have formed in a similar way by a convergence of the oceanic plate and a continental plate.

Deb: Is it the same situation in Honduras? Isn't there a small plate that's subducting there?

Dr. Bob: There's a real small plate. That's why in Honduras and Guatemala and in parts of Central America and Mexico, there's a tremendous amount of volcanic activity. What also is associated as a "disaster" to humans living in those areas when the plates converge? The potential for earthquakes. So that 20-million-plus people in Mexico City live under the volcano. Mt. Popocatepetl is very close by. You can see it from Mexico City on a clear day, and it has been active again. Volcanic ash and smoke have been coming out. Quito, Ecuador--there's a massive volcanic cone that's just on the mountain to the west and just towers over the valley site of Quito. So there are many cities in both Central America and South America that live under the threat of the volcano. In the United States, the Mammoth ski area in California is sitting in a massive zone of potential volcanic activity. Flagstaff, Arizona, is built on the flanks of a volcano. You just go north of Flagstaff and it looks like those volcanoes erupted just a couple hundred years ago. You know what? Those volcanoes erupted just a couple a hundred, actually a couple thousand years ago. It looks very, very fresh. It's just that it's quiet at the present time.

If any of you have been able to get to the Grand Canyon, the national park is great. The national monument, which is down river, as you stand at the south rim in all the typical tourist sites you want, or else take a couple hour drive on very, very rugged back roads to get to the Grand Canyon National Monument on native American land. Suddenly you see Vulcan's Throne--black rock spilling down into the Grand Canyon. Did you know that not that long ago geologically, the Grand Canyon was dammed at that location by a volcanic lava flow? There was a massive lake. If you had been there at the south rim looking into the canyon at that time, you would have seen a lake fill. The Colorado River was dammed by nature, not the Glen Canyon Dam, not Hoover Dam. It started out as Boulder Dam but was renamed Hoover Dam. But why is there no natural lake in the Grand Canyon today? The river cut through it. So there's hope yet that some day rivers will cut through Glen Canyon Dam or Hoover Dam.

Let's look at the divergent motions of plates. If we go to the overhead, we find that the divergent--there are only two types. Ocean-ocean pull apart. That's the mid-ocean rift. And the best example is the Atlantic. When that happens, it allows magma to come up because it tears apart. There's a tear in the earth's surface. This can also happen, this rifting, on continent-continent. If you are at all interested in the origins of man, the Leakeys, now the son, continuing that archaeological dig in Africa, where is the big archeological site in Africa as an example of continent-continent tearing apart? The rift valleys of Africa. Are there volcanoes? Yes, indeed. Perhaps you're aware of the fact there are footprints. The first hotfoot occurred about a million and a half years ago as some bipedal ape-like man, man-like ape, the early relatives, walked across still cooling basalt and left footprints in the basalt. They're there. Can we get an absolute date on that? You betcha, on the basalt itself. We know that it's a very close date because the footprints must have occurred when it was still soft.

Deb: Now, would Iceland be considered an ocean-ocean pull apart?

Dr. Bob: Iceland is ocean-ocean because it is an island you see on the ocean plate. It's the land of fire and ice, isn't it? So it's an island, all of this black rock, and it's really pulling apart and the volcanic activity is not real spectacular in this case. In the convergent case, those are spectacular volcanoes.

The final type of plate boundary is a transform fault, and they'll always be kids in class who know about this. Ocean-ocean transform faults are hidden from view, under the sea floor. They occur, and I'll show this pattern for the spreading center. There's a fault in the spreading center and you see an offset. Why? Because we're talking about rigid plates on the surface of a near sphere-like object and there are places where there have to be little adjustments. That's what these transform faults do. The transform faults allow for the adjustment in the displacement. Then, this is the one they all know about, because there is not an example of continent-ocean transform fault but there sure is a continent-continent transform fault. Where in the United States is the greatest potential for earthquakes and the best known fault in the lower 48 states? San Andreas. In these faults, this is kind of interesting, in California, there's this part and LA is right here, and on this side, here's the fault. LA and the rest of California, this is all the metropolitan area, so there's more coastline. San Francisco is up here on the other side of the plate. The relative movement is shown like that. I only put one arrowhead on that because it's side-to-side slippage. So if you come back in 10-million years, you might be able to walk from LA into San Francisco and they would be neighbors, they'd be suburbs. Which is the suburb of which will be a very interesting political discussion. And why do we say in 10-million years or so? Because it's moving at a rate of about three to four centimeters per year. What is the width of the Atlantic Ocean? A good way to incorporate mathematics into the science class. It's kind of a shame classrooms all need globes. All too often, we talked about that last week, we have maps and the projection distorts continents. Take a globe and measure it, find the scale, and find out how far apart is the coast of North America. Here's Florida, here's the east coast, and the coast of Africa. How far apart are they? And at what rate would you have to move them to either bring them back together or once they were together to move them back apart? How long would it take? Check that out--come back with that answer. We'll talk about it later. So these are components and examples of plate tectonics.

Why are plate tectonics critical? Because they create the shape and form of the earth, but they also have a very important ramifications for life on earth. Some of the continents have been together in one large mass called Gondwana Land. Gondwana Land is a reassembly of Africa, South America, Antarctica, India, and Australia. It's the southern hemisphere. The northern hemisphere had a different name and they were all once pretty much together as Pangea. But when there was Pangea, what is there a very limited amount of? There's all one land mass. There is a very limited amount of shallow water adjacent to a continent in warm water environments, right? And our shallow water near continental environments, I mean shallow water, are they rich in invertebrate life and therefore vertebrate life also? Tremendously prolific. So if we spread the continents apart, there's a greater potential for shallow marine environments in warm water conditions to enhance and support the marine invertebrates on the bottom and inside the sediments offshore. If plates are going to be coming together and there are going to be volcanoes, what will volcanoes do to the climate? Potentially change it. If it changes the climate, what's going to happen to the plants? Plants may become endangered. If plants become endangered what about plant eaters? If plant eaters become endangered what about the meat eaters that need the plant eaters? So you can see the sequence of events, the connections between plate tectonics and the events of life. Life is punctuated by extinctions. Extinctions are very much a part of life. They are so very critical and there were critical times in earth's--we will come to find where extinctions are significant; 40, 50, 60 percent of living forms did not survive. In many cases, it has to do in connections with systems and events of very active plate tectonics. So that connecting link is very critical. When we talk about this, we have to talk about the diversity of life.

I've introduced a few aspects, Deb, of the diversity of life. Where are we these days? What did some of us learn? I'm a near fossil with respect to what I learned when I came through geology. Where are we in the kingdoms of life?

Deb: We now have six kingdoms. Everybody's starting to shift over now. We all learned, most of us anyway, a five kingdom system classification. They've been teaching that for years. Now, just recently, there's been a suggestion that we adopt a six kingdom classification system. A lot of the colleges are now starting to teach that as a option, a six kingdom classification. As a matter of fact, your book presents six kingdoms and so we want to prepare you for that when you go to look at the book. For those of you that taught this kingdom, the minarans included all of the bacteria. Now biologists are thinking twice about this and deciding that we really shouldn't be lumping all these bacteria together. We should be taking a look at some of these bacteria that live under extreme conditions and placing them into a separate kingdom which they call archeobacteria, which means ancient bacteria. These bacteria live under extreme conditions like in volcanic vents or at the bottom of the ocean floor. They either require very low oxygen levels or extreme temperatures, or high acidity. They don't have the same genetic code as the u-bacteria or the second kingdom now that we have taken them out of the minaran kingdom. So we have the archeobacteria which are also known as the extremophiles because of the places that they inhabit.

Dr. Bob: They love extremes.

Deb: Right. So archeobacteria meaning ancient bacteria and u-bacteria actually translating as true bacteria. So this will then constitute the archeobacteria and become the sixth kingdom and the true bacteria are taking the place of the old minaran kingdom that we used to have. So that would be two of our kingdoms.

Then another kingdom that we would go to is the plant kingdom rather then going from simple to more complex. Let's take a look at how they acquire food as a way of separating these things. We'll go to plants next because they are producers or produce their own food. We've got nonvascular versus vascular plants. Nonvascular plants are things like algae that don't have transporting networks for nutrients and water, as opposed to vascular plants which do transport nutrients and water back and forth between the roots and the stems or through some system throughout the plant. The vascular plants can then be divided up into these seedless versus seed plants. So we have two divisions here. An example of the seed plants might be a fern. They produce seeds and seed pods. So the seed plants then can be divided up into things we call gymnosperms and angiosperms. For all those bio majors running around out there, this should sound very familiar. The gymnosperms are naked seeds. An example of one of those might be our bristle-cone pine that we saw earlier. So the cone-bearing plants then are the gymnosperms. Then, angiosperms would be all of those flowering plants. Don't take copious notes on this because the book does a really nice job of laying this out for you. You can take a quick review in the book if you need to. The key here is that the plant kingdom relies heavily on photosynthesis. The plant kingdom produces its own food. Even though there's a variety of plants we find under there, that's the key that separates plants from other kingdoms as opposed to what we were looking at before, which were the bacteria that are really very simple organisms that lack a real cell structure that we're used to seeing in other kingdoms.

From the plants lets move into the fungi, which is actually a recent kingdom. We supported a four kingdom classification for a really long time and it wasn't until the 1970s that we actually considered fungi a separate kingdom altogether. These would be examples--might be a yeast or a mushroom. The members of this kingdom have a slightly different way of acquiring nutrients rather then producing their own food. They are consumers or decomposers. Primarily, we think of mushrooms as decomposers because they grow on dead material. For the longest time, we categorized fungi in with plants for the wrong reasons. They obviously don't produce their own food so it makes natural sense to put them in their own kingdom. The difference then between fungi and animals is that they absorb food into the cell, and it's within the cell that they actually digest their food. That's what distinguishes fungi from other kingdoms. They actually absorb and then digest, which is different than the animal kingdom.

We should go to the animal kingdom next. We won't say really a lot about the animal kingdom because we're going to be spending the rest of the semester on the animal kingdom. We're just going to briefly mention that the animal kingdom consists of both invertebrates and vertebrates. Those things with a backbone and those things without. The animal kingdom, then, consist of consumers. There are no producers. We don't photosynthesize, much like the fungi kingdom. The difference here being that in the animal kingdom, we digest food external to the cell and then we have some system of bringing the nutrients then into the cell once it's been digested. So the cell then uses digested materials. That's kind of a distinction, then, between the plant and the animal and the fungi.

So what's left? What's left is kind of the landfill of kingdoms and that's where we throw everything else, everything that doesn't fit someplace else and that's the protos kingdom. It's a dumping ground because we place in the protos kingdom both the algae and the protozoas which have sort of plant-like cells and animal-like cells. They're mostly unicellular but not all. They contain both things that photosynthesize and both organisms that consume. It really is kind of a hodgepodge of whatever's left.

So those are the six kingdoms that we'll be using for this semester. We'll be taking a look at the fossil remnants of those six kingdoms or most of those anyway. Specifically in West Virginia, we'll be looking at lots and lots of invertebrates.

Dr. Bob: What I would like to just throw in here as we come to the end of the show is that we find fossils out of all the kingdoms, but by far the most abundant variety and preservation are the animal kingdom, especially when they got hard parts. Before some of those had hard parts, those invertebrate forms were very hard to fossilize. The plant kingdom we find more and more spectacular reflections of the plant leaves, imprints. The more we dig the more we find. There's some spectacular things we're going to talk about. But beyond those, the other four, there are fossil records. They're not great. In some cases they're microscopic. As a result, we look at the history of life and all the kingdoms. I've often thought, do we find fossil cacti? Can be tough, but in some volcanic areas you could bury some catastrophically. Fossil mushrooms? I don't know, I've never seen any.

Deb: They said that the tendrils, sometimes the mycelium get preserved.

Dr. Bob: That would, they would indeed. We're down to the final two minutes and I'd like to call your attention to quiz number one. There are four questions on quiz number one, and they're very general questions. There are no specific answers. You do not have to turn that in to us anytime soon. We'll talk about this again next time. Talk about it among yourselves. We are eventually going to put all the other quizzes on the web site. We will get this information out there, but look at these four. Talk among yourselves, but each person write their own answer, please. Think about what we have started to talk about. We will cover this in greater detail the next time.

Our next broadcast is Wednesday, February 10th. Facilitators please send in the materials, participant names, and addresses so that we can get books out. The books will be mailed this week.

Until next time, take care, think about geology, and look at the rocks at the side of the road!

WVGES Education Specialist, Tom Repine (repine@wvgs.wvnet.edu)

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