Geologic Time Flashcards
(18 cards)
Uniformitarianism
Principle stating that geologic processes that occur today are similar to those that occurred in the past.
Absolute age
The numerical age, in years, of a rock or object
Relative age
The age of rocks and geologic features compared with other nearby rocks and features.
Superposition
Principle that in undisturbed rock layers, the oldest rocks are on the bottom.
Original horizontality
Principle that most rock forming materials are deposited in horizontal layers.
Lateral continuity
Principle that sediments are deposited in large, continuous, sheets in all lateral directions.
Inclusions
A piece of older rock that becomes part of a new rock.
Cross-cutting relationships
The principle that if one geologic feature cuts across another feature, the feature that it cuts across is older.
Fossils
The preserved remains or evidence of past living organisms.
Mass extinctions
The extinction of many species on Earth within a short period of time.
Unconformities
A surface where rock has eroded away, producing a break, or gap, in the rock record.
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.
Index fossils
A fossil representative of a species that existed on Earth for a short length of time, was abundant, and inhabited many locations.
Key bed
A rock or sediment layer with distinctive characteristics that make it easily identifiable in correlation.
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 five 5 principles of relative age dating?
- Superposition
- Original horizontality
- Inclusions
- Cross-cutting relationships
- Lateral continuity
How can fossil records help us learn about the past
- allows us to trace the evolution of various species - - by observing how fossils become more complex as time goes on
- make it connections between species by studying the similarities of the fossils
- It can also be used to predict when mass extinction events occurred as there is a sudden change in the fossils found
How are unconformities made?
Weathering, erosions, volcanic events, and other natural processes.
