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動画の字幕をクリックしてすぐ単語の意味を調べられます!
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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.
コツ:単語をクリックしてすぐ意味を調べられます!

読み込み中…

How do Fossils Form?

753 タグ追加 保存
羅紹桀 2015 年 8 月 24 日 に公開
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  1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯,不妨使用「俚語字典」,或許會讓你有滿意的答案喔