Unconformities Flashcards
(92 cards)
What is an unconformity?
“a gap in time”
All unconformities represent a break in time or a period where no sediment was deposited.
What may cause an unconformity?
May be the result of a change in the environment or earth movements and erosion
What are the three types of unconformity?
Angular unconformity.
Disconformity.
Nonconformity
What is an angular unconformity?
old rocks tilted or dipped.
Then the unconformity
Younger rocks are horizontal
What is a disconformity?
old rocks are horizontal.
then the unconformity (erosion).
New rocks deposited horizontal.
Difficult to identify but still represent a gap in time
What is a nonconformity?
Older igneous rock is eroded and exposed at the surface.
Then the unconformity.
Then younger sedimentary rocks deposited
What is uniformitarianism?
The theory that the current earth processes have always been as they are now.
Slow incremental changes such as erosion
What is catastrophism?
Sudden, short lived, and violent eruptions.
e.g. earthquakes, floods, volcanic eruptions
What is gradualism?
Gradual (geo time) reform rather than sudden. Rocks found take a long time to form
Who produced the idea of uniformitarianism?
Charles Lyell
What are the 5 mass extinction events? (names)
Ordivian-silurian
Late devonian
Permo-triassic
Triassic-Jurassic
Cretaceous-tertiary
When was the ordivician-silurian extinction event?
443 Ma
When was the late devonian extinction event?
372 Ma
When was the permo-triassic extinction event?
252 Ma
When was the triassic-jurassic extinction event?
210 Ma
When was the cretaceous-tertiary extinction event?
65 Ma
What is the better known name for the permo-triassic extinction event?
The great dying
(also called End permian)
What is the better known name for the Cretaceous-tertiary extinction event?
KT
What caused the ordivician-silurian extinction event?
Ice age from plants absorbing CO2
What caused the late devonian extinction event?
Drops in oxygen in seas/oceans
What caused the permo-triassic extinction event?
Volcanic activity and climate change
What caused the triassic-jurassic extinction event?
Rising temps from volcanic activity
What caused the cretaceous-tertiary extinction event?
Massive volcanic eruptions, then an asteroid
How many species were affected by the ordivian-silurian extinction event?
86% marine species