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Spot on Science: Let's Talk About Rocks

Even the smallest pebble can teach us a big lesson. Margaret interviews Kevin Magee, president of the Cleveland Geological Society, to talk about the rocks that can be found in Ohio and what they teach us about Ohio's history.

Class Discussion Questions:

1) Why is geology an important science?

2) What important minerals are present in Ohio?

3) What can rocks teach us about Ohio's natural history?

Read the Script:

[Margaret] Ever get a pebble stuck in your shoe? It can be annoying for sure. But even the smallest rocks can teach us a big lesson. To learn a little more I invited Kevin Magee, president of the Cleveland Geological Society to rock it out in the studio. I started by asking him, what exactly is geology?

- So, geology. Geology is technically the study of rocks, but I really look at it as the study of the Earth's history. The rocks, when they were laid down, the minerals were deposited, the world was very different than it was now. It could tell us a lot about what the Earth looked like when those rocks were put down on the surface.

- Neat, so you brought in a lot of Ohio rocks. So, if we look at them like clues, we can find out some more about Ohio's history.

- We can. We can tell what Ohio was like back two, three, 400 million years ago.

[Margaret] Awesome, well let's get digging.

- Okay. So, we have sandstone. This is Berea sandstone, from just south of Cleveland, Berea, Ohio, and at the time when this rock was laid down, we were a river delta. With the division between the ocean and the land, we were right on the edge. And big rivers were carrying eroded rock from big mountains that no longer exist in Canada, to the north, down here and deposited it as the rivers went into the ocean. And then, this right here is coal, and the coal is deposited when we more inland, we were swamps. And again, south of the equator, 300 million years ago, and it's all ferns and trees that don't exist today, all dead and compacted and formed in coal. And then, we have salt here. Salt was laid down in the Silurian about 425 million years ago. And the salt was from this area being an ocean, and then being dried up, then an ocean, then drying up, then an ocean, and we just got layer, upon layer, upon layer of salt. And some of it is light color, some of it's dark color, depending on the minerals that were in the water when the salt evaporated, or the water evaporated.

[Margaret] And so, this isn't the kind of salt I can put on my French fries.

[Kevin] No, I don't recommend putting it on your French fries. It's not the type of salt you eat. But it's very similar related. And it's wonderful for road salt.

[Margaret] A lot of the salt that we see in the winter time getting spread on the roads is from right here in Ohio.

- That's where it comes from, 2000 feet under Lake Erie in Cleveland.

- Neat. What about this next guy?

- So, that is world famous Cleveland shale. It's a very black flaky rock, and it tells us the world back then was under three or 400 foot of ocean, at least here in Ohio. And it was interesting because it was a stagnant sea. There's no oxygen on the bottom of the sea. And nothing could live there. It forms a very dark rock with it does that. But we know that there was life in the upper waters because large fish like Dunkleosteus, the big armor fish. When it died, would drift to the bottom of the sea, and get buried, and fossilized. And so, we know that there were animals living in the upper waters, but in the lowers waters, it was just all black silty, rot stuff that eventually became rock.

- Oh wow. And how about this one? 'Cause this guy's got some interesting kind of seashells in it.

- It does. Yeah, this is limestone. 400 to 450 million years old. It actually all sorts of creatures in it, some you can't even see, little diatoms, things that lived in the water. When they die, they drift to the bottom. They form a lime mud, and then within that, there's also corals and shells, and things like that. And they all eventually get turned into rock together.

- And what do some of these rocks get used for today?

[Kevin] So, limestone you see a lot on gravel driveways, great walls along the lake front. For the sandstone, it was a lot in the past for grindstones and also for buildings. You would see it in building materials, and even making curbs, they used it for curbs as well.

[Margaret] And then, what about the shale? What is that used for?

- There really is nothing that shale is used for. It's just too flaky, and too soft, and so, it just sits there. Nobody uses it for anything.

- Well, we can use it for figuring out more about Ohio's history.

- You know, it does.

- Awesome, well thank you so much for coming, and it's been really interesting.

- Thank you, my pleasure.