1. Earth’s Story
• James Hutton wrote Theory of the Earth.
• Uniformitarianism-states that the same
geological processes shaping the Earth
today have been working throughout the
Earth’s history.
• “The present is the key to the past”

2. • Catastrophism-states that all geological
change occurs suddenly.
• Many people thought that Hutton was
crazy. They all thought that the changes on
the Earth were sudden.

3. Debate
• At your tables number off by twos.
• The ones get together and the twos get together.
• Ones talk and make a list of why
uniformitarianism should be accepted.
• Twos talk and make a list of why catastrophism
should be accepted.
• In ten minutes you will debate with the others at
your table supporting your case.

4. • The works of Charles Lyell helped to get
uniformitarianism accepted.
• There are accounts of catastrophism (e.g.
the asteroid that hit the Earth, that may have
led to the extinction of the Dinosaurs).

5. Relative Dating
• Determining whether an object or event is
older or younger than an object or event.
• Superposition-states that younger rocks lie
above older rocks in undisturbed sequences.

6. • Geologic Column-
an ideal sequence that
contains all the known
fossils and rock
formations on Earth
arranged from oldest
to youngest.

7. Disturbed Rock Layers
• Fault-break in the Earth’s crust along
which blocks of the crust slide relative to
one another.

8. Disturbed Rock Layers
• Intrusion-molten rock from the Earth’s
interior that squeezes into existing rock and
cools.

9. Disturbed Rock Layers
• Folding-rock layers bend and buckle from
the Earth’s internal forces.

10. Disturbed Rock Layers
• Tilting-internal forces in the Earth slant
rock layers without folding them.

11. Unconformity
• A surface that represents a missing part of
the geological column.

12. Fossils
• A naturally preserved evidence of life.

13. Ways that a fossil is formed or
where they are found!!
• They are found in rocks!
• Minerals replace tissue
• Permineralization-minerals fill in pore
spaces of an organism’s tissues
• Petrification-an organism’s tissues are
completely replaced by minerals.

14. Formation and Location Continued
• They are found in amber.
• They are mummified.

15. Formation and Location Continued
• They are frozen.
• They are found in tar.

16. Types of Fossils
• Trace fossils-any naturally preserved
evidence of an animal’s activity.
• Molds-a cavity in the ground or rock where
a plant or animal was buried.
• Cast-an object created when sediment fills a
mold and becomes a rock.

17. Cast and Mold

18. Fossils can tell time
• They can tell when there were changes in
the environment.
• They also tell when there were changes in
life-forms.
• Index fossils-fossils of organisms that lived
during a relatively short, well-defined time
span.

19. Time Marches On
• Geologic time scale-a scale that divides
Earth’s 4.6-billion-year history into distinct
intervals of time.

20. Divisions of Time
• Eons-the largest division of geological time.
• Eras-second-largest divisions of geological
time.
• Periods-the third-largest division
• Epochs-the fourth-largest division

21. ERAS
• Paleozoic Era- “old life” lasted from about
540 to 248 million years ago. There were no
land organisms.
• Mass extinction ended this era. Nearly 90
percent of all species perished.

22. ERAS Cont.
• Mesozoic Era- “middle life”. It lasted from
about 248 to 65 million years ago. Age of
the reptiles. By the end 50 percent
perished.

23. ERAS Cont.
• Cenozoic Era- “recent life”. It began about
65 million years ago and continues to the
present. It is called the Age of Mammals.
Some mammals from the beginning of the
era have now become extinct.