History & Geological Time Flashcards
Branch of geology that deals with origin composition, structure, & classification of rocks
petrology
Study of rock layers (strata) & layering (stratifications)
stratigraphy
Studies life existing prior to Holocene epoch. Includes study of fossils to determine how they evolved & interacted with environment.
paleontology
Represents interval time occupied by geologic history of Earth. Provides meaningful time frame where events of geologic past are arranged
Geologic Time Scale
Places events/rocks in chronological sequence w/o knowing actual age
Relative dating
One cannot tell exactly how many years have passed since an event happened with this method of dating
Relative dating
Principles of relative dating
- Principle of Original Horizontality
- ” Superposition
- ” Cross-cutting Relationship
- ” Inclusion
Sedimentary rocks deposited horizontally.
Principle of Original Horizontality
What does deviation from horizontality indicate
deformation occurred after the deposition
The layer at the bottom of sequence is oldest while successively higher levels are younger
Principle of Superposition
Geologic features like faults or igneous intrusions are younger than rocks they cut across
Principle of cross-cutting relationship
Evaluate: If rock / fragments are included w/in another rock layer, then…
rock fragments are older than the rock layer where they were embedded
Rock fragments older than rock layer where they were embedded
Principle of Inclusion
Places actual ages of rocks/events
Absolute dating
Method of dating:
Based on decay rate of radioactive isotopes within fossils, rocks, and artifacts
Absolute dating
