Journal Entry #3 – Fossils and Relative Dating

Journal Entry #3 – Fossils and Relative Dating

Yay! Old rocks that look like dead stuff! Woooooo!!!! The only thing that could possibly be more exciting would be if the people who made The Hunger Games and

the people who make Hungry Hungry Hippos (you know…the board game) decided to make a new movie where hungry hippos eat teenagers in front of a cheering crowd.

That’ll be awesome! Fossils!!!

• Fossil: The remains of an organism preserved in petrified form or as a mold or cast in rock.

• Fossil: The remains of an organism preserved in petrified form or as a mold or cast in rock. – How?

• Fossil: The remains of an organism preserved in petrified forum or as a mold or cast in rock. – How? • The organism/track/etc. must generally be covered by

sediment quickly

Types of fossilization

• Permineralization – Empty spaces within an organism are filled with mineral-rich water. The minerals precipitate from the water, eventually occupying the empty space.

Types of fossilization

• Casts/Molds – Original remains are completely dissolved, leaving an organism-shaped hole in the rock

Law of Superposition

• In an undisturbed horizontal sequence of rocks, the oldest layers will be on the bottom, with successively younger layers of rock on top of these.

Law of Original Horizontality

• All layers of sediment are originally deposited horizontally. Sedimentary rocks that are no longer horizontal must have been shifted from their original position.

• Index fossil – Fossil that is used to define and identify geologic time periods. – Generally based on organisms that only lived

during specific time periods.