I. Evidence from Rocks

Chapter 12.1

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A. Geology

1. Study of Earth’s formation + structure a. Evidence from rocks + fossils allows

understanding of evolution of life on Earth

B. Rock Cycle

1. Rock formation + recycling

2. Igneous sedimentary metamorphic igneous

3. How sedimentary rocks forma. Bigger rocks break down into tiny rocks

(sediment) because of weathering + erosion

b. Tiny rocks move (water, wind, ice) + form horizontal layers

c. Layers press together into sedimentary rock

4. Law of Superposition

a. Bottom layer of sedimentary rock is older layer than one on top of it because bottom layer formed first

(Miss D’s Theory of Dirty Laundry – on Friday where can you find last Monday’s clothes? On the bottom of the pile.)

b. Rock layers can bend or shift – changes order (what causes the movement?)

c. Things like earthquakes or rivers can interrupt continuous layers

C. Relative dating (relative means compared to)

1. Method of sequencing events in the order in which they happened by comparing them

a. doesn’t tell exact age

b. which happened first – Mickey Mouse or you?

2. Used for fossils

Purpose: to determine the age of an object relative to something else

Looking at the picture what was the order in

which things happened?

3. Cross-cutting (Intrusion)

vein cutting through rock layers

a. Younger than those layers

4. Inclusion

a. Anything trapped in rock when it forms

b. Inclusion had to be there first, older

Quartz with melt inclusions

5. Index fossils

a. Compare to rock containing fossils of known age

Trilobites (marine organisms) went extinct 245 mya

D. How fossils form

1. Organism dies, gets buried in sediment

2. Soft parts decay

3. Hard parts preserved in sedimentary rockhttp://www.classzone.com/books/earth_science/terc/content/visualizations/es2901/es2901page01.cfm?chapter_no=visualization

4. Paleontologist – studies fossils