Download Journal Entry #4 * 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.