Geologic Time Flashcards
(20 cards)
What is Uniformitarianism?
Principle stating that geologic processes that occur today are similar to those that occurred in the past.
What is Absolute age?
The numerical age, in years, of a rock or object.
What is Relative age?
The age of rocks and geologic features compared with other nearby rocks and features.
What is Superposition?
Principle that in undisturbed rock layers, the oldest rocks are on the bottom.
What is Original horizontality?
Principle that most rock forming materials are deposited in horizontal layers.
What is Lateral continuity?
Principle that sediments are deposited in large, continuous, sheets in all lateral directions.
What are Inclusions?
A piece of older rock that becomes part of a new rock.
What are Cross-cutting relationships?
The principle that if one geologic feature cuts across another feature, the feature that it cuts across is older.
What are Fossils?
The preserved remains or evidence of past living organisms.
What are Mass extinctions?
The extinction of many species on Earth within a short period of time.
What are Unconformities?
A surface where rock has eroded away, producing a break, or gap, in the rock record.
What is Correlation?
A method used by geologists to fill in the missing gaps in an area’s rock record by matching rocks and fossils from separate locations.
What are Index fossils?
A fossil representative of a species that existed on Earth for a short length of time, was abundant, and inhabited many locations.
What is a Key bed?
A rock or sediment layer with distinctive characteristics that make it easily identifiable in correlation.
What is the Geologic time scale?
A chart that divides Earth’s history into different time units based on changes in the rocks and fossils.
What are the principles of relative-age dating?
- Superposition
- Original horizontality
- Inclusions
- Cross-cutting relationships
- Lateral continuity
What does the fossil record allow us to do?
Trace the evolution of various species by observing how fossils become more complex over time.
What can the fossil record predict?
When mass extinction events occurred as there is a sudden change in the fossils found.
Why is the fossil and rock record not truly complete?
Due to weathering, erosions, volcanic events, and other natural processes leading to unconformities.
How can we use the fossil record?
To draw conclusions about the origins of life.
