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catastrophism
episodically events such as severe climate changes, astroids etc that cause extinctions and other odd events
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Uniformitarianism
dominates the day to day process
(uniform natural laws geological processes) slow changes throught time. Cycles
the present is the key to the past
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Stratigraphy
- The study of layered rocks.
- Stenos law basis of stratigraphy
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Principle of Superpostion
oldest rocks are on bottom and youngest rocks are on top
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principle of original horizontality
sediments deposited in flat orizontal layers
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principle of original lateral continuity
sediments are depostited over a large area in a continuous sheet
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Fossil Preservation
Desiccation- drying or mummification
best for hard sells, bones, teeth. Rapid Burial
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unconformity
- 2 flat beds then erosion creates a gap in time
- unconformity is younger than the rock that is erroded
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Actualism
natural laws both past and present
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principle of cross cutting relationships
- fault or whatever is youngers than the rock it cuts.
- sediments rocks are younger than the fault which cuts them.
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Principle of inclusion
- fragments of the eroded rock overlie the unconformity. these are called clasts or inclusions
- the pieces of gravel are older than the beds in which they are found.
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xenolith
- fragment broken off during intrusion and fallen into magma(igneous rock). it is a fragment of the surrounding rock.
- xenolith is older than the igneous rock which contains it
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primitive rocks
- deposited by a hot mineral rich ocean
- formed the cores of mountain ranges
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transition rocks
- deposited when earth became suitable for living
- sandstone, shales, coals
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Alluvium
loose gravel, sand, clay lay on transition rocks
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natural selection
- produces more offspring that can survive
- morphology(form and structure)
- physiology(organs and functions
- compete for food and habitat
- traits good survive adn pass those traits
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