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  • YouTube, its Cram. How do Fossils form? They're not just bones that end up underground waiting

  • to be dug out. The word fossil itself comes from the Classical Latin word Fossilis, which

  • means obtained by digging. But as we know some fossils can be obtained without digging.

  • There are 4 types of fossils, mold, cast, trace and true form fossils. Mold fossils

  • are impressions, without the bones themselves. Cast fossils are basically mold fossils but

  • are filled in, typically with minerals. Trace fossils are traces of the existence of the

  • creature, such as nests, burrows or tracks. True form fossils actually have parts of the

  • animal, typically bones. There are many types of true form fossilization, but two main kinds

  • are unaltered preservation and permineralization, which is what we will be focusing on today.

  • Unaltered preservation is most common in insects and other small creatures. It is when they

  • are trapped in a thick substance which hardens, preserving all parts of their body. This substance

  • is typically amber, which is hardened tree sap. permineralization is when rock like minerals

  • seep into the animal and replace its organic tissue and sometimes bone. This is why fossilized

  • animals seem to have dense bones, it is because of the minerals that seeped in. One way this

  • can happen is in a body of water. The animal will settle at the bottom, and the decomposition

  • process will be greatly slowed by the surrounding water. Eventually sediment will cover the

  • body, and more and more layers of rock will cover it on top. This pressure will cause

  • permineralization. Eventually, due to geologic forces, the fossils may be closer to the surface

  • or even above ground which is where we can discover them. Though now without technology

  • and our knowledge of migration patterns and habitats we can accurately predict and find

  • fossils underground, in the past we had to rely on chance to stumble upon something great.

  • I hope you enjoyed this video as much as I appreciated you watching. Subscribe to stay

  • up to date on all my latest science videos, and until next time, Cram out.

YouTube, its Cram. How do Fossils form? They're not just bones that end up underground waiting


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B1 中級 美國腔

化石是如何形成的? (How do Fossils Form?)

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    羅紹桀 發佈於 2021 年 01 月 14 日