Friday Sprog Blogging: rocks and erosion.

Yesterday afternoon, I attempted to talk with the younger Free-Ride offspring about erosion. It would seem, from our conversation, that it is not just rocks that can erode — recall of material learned in science class can also erode, as can patience.
Below is a rough transcript of our chat. I’ll see if I can clean up the audio and put the MP3 up as a SprogCast by sometime this weekend.
Dr. Free-Ride: I wanted to ask you what you can tell me about rocks. I think you learned a little about rocks in school, didn’t you?
Younger offspring: No.
Dr. Free-Ride: No? Did you learn something about different kinds of rocks?
Younger offspring: No.
Dr. Free-Ride: No? Am I thinking about your sibling?
Younger offspring: Yes.

Dr. Free-Ride: Do you know … well, what do you think you might know about rocks? What have you noticed about rocks?
Younger offspring: Nothing.
Dr. Free-Ride: You don’t know anything about rocks? Like, if I put a rock in front of you, you wouldn’t know what it was?
Younger offspring: I would know what it was.
Dr. Free-Ride: Well, how can you tell a rock from other stuff? What are rocks like?
Younger offspring: Hard.
Dr. Free-Ride: Are all of them hard?
Younger offspring: Yes … except for minerals.
Dr. Free-Ride: Oh. What can you tell me about minerals?
Younger offspring: I don’t know.
Dr. Free-Ride: Huh.
Younger offspring: I forgot all about it in science class.
Dr. Free-Ride: Oh, so you learned something about it in science class, but it maybe leaked out a little bit, or it’s in cobwebs?
Younger offspring: Yes, ’cause it’s summer!
Dr. Free-Ride: I understand that it’s summer, but you’ve walked on rocks and things that are like rocks and things that are made of minerals.
Younger offspring: Well, at least I know that they hurt when you walk on them.
Dr. Free-Ride: Always?
Younger offspring: Well …
Dr. Free-Ride: What about on Sunday before we got in the car? Where did we go with Uncle Fishy and RMD?
Younger offspring: Where?
Dr. Free-Ride: Where did we go with Uncle Fishy and RMD?
Younger offspring: Oh yeah, those are finely crushed rock.
Dr. Free-Ride: What are?
Younger offspring: Sand.
Dr. Free-Ride: Sand. And are those —
Younger offspring: But I’m talking about at Lake Elizabeth. I went in that artificial lake —
Dr. Free-Ride: OK
Younger offspring: — and I felt the rocks in there, and ouch! I went all the way from the rocks that were closest to the table to that artificial place.
Dr. Free-Ride: Uh huh.
Younger offspring: And it was painful.
Dr. Free-Ride: Was it painful just because the rocks were hard, or were they also pointy?
Younger offspring: Hard and pointy.
Dr. Free-Ride: Pointy. OK —
Younger offspring: The point is that they hurt.
Dr. Free-Ride: The “point” is that they hurt. OK, so do you think that if they had been rounder, maybe they would have hurt less?
Younger offspring: Yes, but if there’s so many — like, there was this big rock, and this rock right next to it, and it slanted like this, and then there were all these pebbles in here.
Dr. Free-Ride: OK.
Younger offspring: And they really hurt when I tried to step in it.
Dr. Free-Ride: OK, so —
Younger offspring: And they were round pebbles, but it hurt.
Dr. Free-Ride: Round pebbles but they hurt? Maybe because they were small enough that your weight on them was sort of all concentrated on their little —
Younger offspring: They weren’t this small, they were this small.
Dr. Free-Ride: OK, so they were about the size of a —
Younger offspring: Egg.
Dr. Free-Ride: Of an egg, OK. All right. So, I think you know some ways that rocks get made, or at least you used to before the cobwebs took over.
Younger offspring: Minerals.
Dr. Free-Ride: Well, do you remember what an igneous rock is?
Younger offspring: No.
Dr. Free-Ride: No?
Younger offspring: No I don’t.
Dr. Free-Ride: Do you have a guess?
Younger offspring: No.
Dr. Free-Ride: Do you know what a metamorphic rock is?
Younger offspring: No.
Dr. Free-Ride: Do you know what a sedimentary rock is?
Younger offspring: No.
Dr. Free-Ride: No?
Younger offspring: No.
Dr. Free-Ride: You don’t have any guesses at all?
Younger offspring: No.
Dr. Free-Ride: OK. Tell me about sandcastles, then. Sandcastles, if you build them by the edge of the water … what happens to them, eventually?
Younger offspring: They get washed up.
Dr. Free-Ride: They get washed up. Why? How does that work?
Younger offspring: Water.
Dr. Free-Ride: What does the water do?
Younger offspring: It absorbs in the sand.
Dr. Free-Ride: Does it absorb, or does it (sound like a wave crashing)?
Younger offspring: It goes over and it absorbs.
Dr. Free-Ride: OK, so it makes the sandcastle wet, but if the sandcastle … so, the water sort of comes —
Younger offspring: It gets knocked down.
Dr. Free-Ride: It gets knocked down. Does it get knocked down all at once, or —
Younger offspring: Sometimes, ’cause once I built a bridge like a drawbridge, and I like — at first it was just like a wall and then I put my hand under and I dug under it and flattened it out on the top. Then the water came and knocked down this top part and then it was only two thin walls.
Dr. Free-Ride: OK. So, do you know what they call it when water takes something like the edge of the beach, or a rock, or I guess maybe even a sandcastle and wears it down? Do you know a word that describes that? Or do you want to learn one?
Younger offspring: No.
Dr. Free-Ride: Well, you’re gonna learn one. Erosion.
Younger offspring: Erosion!
Dr. Free-Ride: Erosion. That’s right. So, erosion describes water wearing stuff down. Why does water wear down sand?
Younger offspring: Because of the Grand Canyon.
Dr. Free-Ride: Um, no, although nice foreshadowing there. Why does water wear down sandcastles?
Younger offspring: Ummm, because it knocks it down.
Dr. Free-Ride: OK, you mentioned already that sand is tiny little rocks, tiny little worn down bits of —
Younger offspring: Minerals.
Dr. Free-Ride: Well, what’s the difference between minerals and rocks?
Younger offspring: Minerals are inside rocks.
Dr. Free-Ride: OK, minerals are what rocks are made up of, and sometimes a rock is made up of just one kind of mineral, and sometimes it’s made of more than one kind of mineral? Yeah?
Younger offspring: Yeah.
Dr. Free-Ride: OK. And there’s minerals in things that aren’t rocks. Did you know that you have minerals in you?
Younger offspring: Yeah.
Dr. Free-Ride: Where? Where are some of the minerals in you?
Younger offspring: Skin.
Dr. Free-Ride: Really?
Younger offspring: Lips, eyes.
Dr. Free-Ride: You know the first place I would look for minerals in you — for big concentrations of minerals in you? In your bones, and in your teeth. Those are the first places I would look.
Younger offspring: And then eyes!
Dr. Free-Ride: Well sure, I guess. Is sodium a mineral?
Younger offspring: Yeah.
Dr. Free-Ride: There’s sodium running all through you, and potassium as well, right?
Younger offspring: Yeah. Sodium is salt.
Dr. Free-Ride: Well, NaCl, sodium chloride, is table salt. But pure sodium is squishy and it reacts violently with water or air.
Younger offspring: (placing a fingertip on a closed eyelid) This is squishy. My eyes are squishy.
Dr. Free-Ride: Don’t squish your eyes, please.
Younger offspring: But they are squishy! I felt them before.
Dr. Free-Ride: I know, and we’ve blogged about that before. But please don’t feel them!
Younger offspring: I felt them before!
Dr. Free-Ride: But don’t feel them now, ’cause —
Younger offspring: I know, but they are squishy!
Dr. Free-Ride: I understand. So anyway, we were talking about — so water will wear down sandcastles pretty easily, because you might say, this sandcastle’s just a pile of tiny little rocks sort of stuck together for the time being —
Younger offspring: But it’s wet sand!
Dr. Free-Ride: But it’s wet sand, and the wet sand sort of holds it together better than dry sand would hold it together. But water, of course, can wear away something made of tiny little pieces —
Younger offspring: And water.
Dr. Free-Ride: — because the waves are strong. But did you know that water can also wear away at what you would consider a great big solid rock?
Younger offspring: I don’t know.
Dr. Free-Ride: It can.
Younger offspring: Yes.
Dr. Free-Ride: And that’s why you said —
Younger offspring: A tsunami wave can knock down a rock and then it got into pebbles and then a tsunami knocked over the pebbles and it became sand.
Dr. Free-Ride: But you know, it doesn’t take, necessarily, a tsunami wave. Even just a little trickle, if you kept it going and gave it enough time, could wear down rocks. If you had a little trickle on a hard rock and you gave it enough time, you could carve the Grand Canyon. Or something like it.
Younger offspring: Ah, can we stop the recording?
Dr. Free-Ride: Well first, I want to know, is there anything you’d like to learn about erosion.
Younger offspring: Not now.
Dr. Free-Ride: Well, at some point in the future?
Younger offspring: Yes.
Dr. Free-Ride: Can you think of a couple questions we can keep track of so that later we try to discover something.
Younger offspring: OK, I’ll write down that we want to speak about erosion some other time, OK?
Dr. Free-Ride: You don’t want to come up with a question now? You got other stuff to do on your summer vacation?
Younger offspring: Yes, it’s summer, of course!
Dr. Free-Ride: You know, science happens during the summer, too.
Younger offspring: (sings a falsetto sign-off note)
Dr. Free-Ride: OK, bye younger offspring.