Unit Six - Geologic Time - Relative Dating Flashcards
What is Uniformitarianism?
The idea that forces working on our earth NOW worked on our planet in the PAST
What is Relative Dating?
Determination of the age of a rock or event in relation to ages of other rocks and events
What is the Principle of Superposition?
Idea that the bottom layer is the oldest, and the layers above are younger.
What is Original Horizontality?
Rocks are deposited in parallel layers
What are extrusions?
Molten rock flows onto the surface
What are intrusions?
- An exception to the principle of superposition
- Molten rock squeezes into preexisting rock layers
- It is younger
What is contact metamorphism?
Temperature change of preexisting rocks along an intrusion
What are faults?
A crack in the bedrock where movement has occured
(Younger than the rocks that they crosscut)
What are folds?
When thrusting rock layers cause preexisting rock layers to overturn.
Definition of Index Fossils
Remains or evidence of former living things used to identify geological periods
What are the two factors needed for fossils to be considered index fossils?
- The organism has to exist over a large geographic area
- The organism existed over a short time
Definition of Geologic Time Markers
Deposits spread over large areas that represent a specific date
