So, this is the really long one! It’s also really scientific… I hope my version of the facts makes sense! 🙂
Also, it looks like I’ll be doing Book Reviews through April. Five more, and then we’ll see what things look like.
Okay: here goes. Have fun, and (if it makes any sense) learn something new! 🙂 I added in the first few lines of the conversation that were in Part #4, just to make sure it made sense! Oh! and I came up with a name for this one: “Cassie’s Question.” 🙂
It took me a full five minutes to work up my courage to ask a question. “Uncle Jonathan?”
“In that picture you showed me last night… of the mammoth… how do we know what they look like?”
“Because of fossils like this.”
“You said fossils like this are rare—what sort of fossils do you usually find? Have we found dinosaur fossils like this?”
“Nope. Just mammoths,” Uncle Jonathan was quite decided on that point.
“But I’ve seen pictures of dinosaurs. Did people just make those up?”
“Most of them. All we have of most dinosaurs is the bones.”
“I’m glad you think so.”
“Why?” I asked suspiciously.
“Because it shows we have something in common. It bothers me too.”
“Oh! of course,” I faltered, for lack of anything else to say.
“So, why do we just have the bones? What happened?”
“Well, hard things are fossilized more easily.”
“Well,” he said slowly, as if trying to decided what to say. “Do you know how fossils form?”
I pondered that question for a moment, before replying, “No, not really.”
Uncle Jonathan shook his head at Dad. “My own niece. What have you been teaching her?”
“Do most people know that, Dad?” I asked, trying to be respectful, and not show that I felt reproachful. I thought you didn’t care, Cassie! I scolded myself.
“It will be in your science book next year,” Dad explained, smiling.
“Do you mind spoilers?”
I turned, somehow surprised, toward Uncle Jonathan. “No, I don’t.”
“Then I’ll tell you how fossils form.” he cleared his throat impressively and began talking rather quickly, “There are three kinds of fossils: molds and casts, petrifaction, and carbonized remains. A mold is formed when an organism is pushed into a soft substance, and then decays leaving an imprint in the substance. These fossils are best preserved when the substance hardens into rock, though technically footprints in the mud are molds too, they just wash away when it rains next. Now casts are made–”
“I’m really sorry,” I interrupted, “but… I’m lost.”
“Sorry,” my uncle said, “Let me try start over: there are three ways that fossils form. Scientists call them molds and casts, petrifaction, and carbonized remains. A mold is made when something leaves an imprint somewhere. Does that make sense?” I nodded. “So when an animal walks past a stream and leaves footprints in the mud, those are molds. The way molds are preserved is when the substance hardens into rock.”
“Mud can turn into rock?” I asked, cocking my head.
“Do you know how rocks form?”
“Uh, no. Not really. I thought they’d been since Creation.”
“Well, some of them might. I don’t know. But new rocks form too. Sedimentary rocks are formed from sediments, when they are pressed together and, usually due to heat or pressure, harden into rock. Are you following?”
“I think so,” I said truthfully.
“Good. So when footprints are formed, the creature puts its foot down, makes the print, and then moves on. Fossils are formed when a dead creature is embedded in a substance.” ONCE-living, I thought ruefully. “The substance then hardens into rock around the creature. When the remains decay, they leave the imprint in the rock. That is why hard things like bones are more often fossilized, because they don’t decompose as fast. Got that?”
I nodded slowly. “Yeah…”
“Okay. A cast is formed when a substance fills a mold, and then hardens into rock in that shape.”
“Oh…” I said rather excitedly, this being the first thing he had said that went home quickly.
Uncle Jonathan smiled. “So that is how molds and casts are made. Then there’s petrifaction. The definition of that is: The conversion of organic material into rock. That happens when an organism is submerged in mineral-rich water. Living tissue is filled with pores, which the water flows into. When the water evaporates, the minerals stay behind. Those minerals then harden into rock while the organism decays, replacing it with rock.”
“Oh,” I said. “So it isn’t conversion, it’s replacement.”
“Well, yes, I guess it is. You’re a thinker!” Why does that surprise me, coming from you? I asked asked myself mentally. My uncle continued, “Is all this new information just going to go in one ear and out the other, or should I tell you about carbonized remains?”
I almost asked if he could tell me tomorrow, but Dr. Peterson happened to laugh at the question, which did me in. “Go ahead!”
“Okay. Carbonized remains form when an organism is buried in sediment, and the liquids are forced out of the organism. This, due to chemical reactions, leaves a thin film on the rock, composed mostly of carbon—hence the name.” I congratulated myself on my incredible self-control for not commenting on how absolutely grotesque that was. “This,” Uncle Jonathan continued, “leaves a ‘drawing’ (making air-quotes with his fingers) of the organism. All organism are made up greatly of water, but plants have more liquid in them than others, so carbonized remains are more often found of them.”
“Wait,” I interjected. “There are fossils of plants?”
“Yes. Once-living organisms includes plants, because they’re technically alive. You know about that, right?”
“You hear about fossils of things like dinosaurs the most,” he went on. “But the majority of the fossil record is small, hard-shelled creatures, like clams.”
“Because hard things are more often fossilized?!?!” I almost shouted, excitedly that I knew something.
“Right! You catch on fast!” my uncle said smiling. Even Dr. Peterson looked impressed.
Okay, next one’s the end! I can’t believe it’s already almost over… but half of me can’t believe it took this long–it’s okay if you don’t understand me; I don’t really understand myself.
And after that, the new thing…