Structural geology The movement of the Earth's plates causes stress and strain on the surface of the Earth. P

Rocks can deform by folding or faulting

Folds When there are compressional forces folds can form 2 basic types: anticlines-- layers go up like an anthill synclines-- layers fold down

Folds that fold upward are anticlines

Folds that go down are synclines

If there is too much stress faults can form. In a fault the rock breaks when stress exceeds strain

There are three types of faults. Normal Reverse Strike –Slip

Fault Terms The wall that overhangs the other is called the hanging wall The wall whose toe is under the other is the footwall

Normal fault Normal fault Formed from tensional forces Hanging wall moves down

Reverse fault Formed from compressional forces Hanging wall moves up

Strike-slip fault Formed from shear forces. Plates slide past each other

Thrust fault Thrust fault—low angle reverse fault

Folding and Faulting

Uniformitarianism The present is the key to the past James Hutton, the Father of Geology What we see now is what has happened in the past Idea popularized by Sir Charles Lyell The Principles of Geology

Catastrophism Earth has been shaped by major catastrophes in a short amount of time

Art work inspired by the idea The Future of Catastrophism

Archbishop James Usher 1664 in Ireland Said Earth began 4004BC Based on Genesis Added up genealogies October 23, 4004 BC

Attention!Achtung! For your semester final, you may use returned papers and notes, but not your book You may only use them if they are in a notebook, NOT loose from your book!

Relative Dating In 1669, Nicholas Steno outlined basic principles for determining relative ages in rocks P

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Principle of Original Horizontality Sed layers were originally deposited horizontally So, sed layers that are not horizontal have been deformed

Sed layers extend laterally to the edge of their basin or thin to nothing Principle of Lateral Continuity

3. Principle of Superposition The oldest layers are on the bottom Younger Older

Principle of Inclusion Included stuff is older than the intrusion

5. Principle of Cross-cutting Relationships Any feature that cuts across a rock or sediment must be younger than the rock or sediment it cuts

Review the Principles one piece of bread was there for me to spread the PB (or J) on (principle of superposition); the bread had to be (relatively) flat for me to spread the peanut butter on it (principle of original horizontality);

the peanut butter probably covered the entire piece of bread (principle of LATERAL continuity); if I slice the sandwich, all those layers (PB, J and bread) had to be there for me to cut through them (principle of cross cutting relationships;

if there is jelly in my peanut butter, I put the jelly on first - and vice versa (principle of inclusions).

Assignment Work from the bottom up using the principles you just read about

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