Impacts 1 Flashcards
List the major subdivisions of the geological time scale
Paleogene - 65 Ma
Cretaceous
Triassic - 251 Ma
Permian
Devonian
Ordovician
Cambrian - 543 Ma
Relative time scale between the two eons
Precambrian - 4.5 Ga
Phanerozoic - 543 Ma
Describe the concept of a biosphere within the Earth System
- Biosphere is parts of earth where life exists
- allowed us to reconstruct components of the past thanks to fossils
Explain how the Biosphere has evolved over time
What are the four principles of stratigraphy?
- Law of Superposition
- rocks on top are younger - Principle of Original Horizontality
- even if strata are tilted today, they were originally flat - Principle of Lateral Continuity
- layers of rock can often be traced out laterally ex/ Grand Canyon - Principle of Cross-Cutting Relationships
- a rock cutting through another must be younger
What is faunal succession?
The change of fossils over time, because of evolution.
-> this makes biostratigraphy possible
What are ideal fossils in biostratigraphy? Name the four criteria.
Index fossils
- common
- wide geographical distribution
- short fossil range (amount of time a species existed for)
- died in good preservation envo (i.e. not in the deep waters)
Name the historical figures in the development of stratigraphy and biostratigraphy
- Nicholas Steno
- Giovanni Arduino
- James Hutton
- George Cuvier
- William Smith
What are the five mass extinctions?
End Cretaceous - 66 Ma
End Triassic - 200 Ma
End Permian - 250 Ma
Late Devonian - 360 Ma
Late Ordovician - 450 Ma
How old is the Earth?
4.5 billion years
What makes up 87% of Earth’s history?
Precambrian
What was the Cambrian Explosion?
- huge flourish of animals and plants that left fossils
- no evidence of life prior to this
- first life was the prokaryotes
What is stratigraphy and the different types?
The study of layers of rock by …
- chrono = time
- litho = rock type
- bio = fossils
- chemo = chemistry
- Nicholas Steno
deeper layers of rock are older
- Giovanni Arduino
started naming layers of rock in the Alps based on depth and composition
- James Hutton
proposed uniformitarianism
- “the present is the key to the past”
- The natural processes that operate today have always operated in the past
Fossils can be used to define _______
Stratigraphic biozones
- two rocks with similar fossil species are likely deposited at similar time
- Biozones can be used to correlate rocks of similar age
- idea was proposed before Darwin’s evolution theory
- George Cuvier
Fossils were once living organisms that can become extinct
- William Smith
fossils can be used to organize the age of rocks everywhere
-> same fossils = same time deposited, even if at a different place
A huge amount of time was organized using ____. This was only possible because _____
fossils
species have evolved
What are unconformities?
period of active erosion or movement that disrupts stratigraphy
The first unconformity
Siccar Point, Scotland
discovered by James Hutton in 1788
Faulting
layers of rocks disrupted/offset by earthquakes
Example of Index Fossils
Ammonites
(251-66 Ma = during the age of the dinosaurs)
What happens after a mass extinction?
Adaptive radiation
- rapid diversification of life into new forms and species
- new ecological niches. envos, resources, etc
What marks some of the key boundaries between geological time periods?
Mass extinctions
Rate of background and mass extinctions
5-10% of species per million years
ex/ the last ice age
greater than 30% of species per million years
Sixth Major Extinction
due to appearance of humans
- 1% of mammals extinct in just 300 years
- current extinction rate is 30k times faster than background rate
What scale do we use to organize Earth’s history?
Geological Timescale
Difference btwn stratigraphy and biostratigraphy
- stratigraphy is the study and organization of layers of rocks
- biostratigraphy is an important part of stratigraphy
-> fossils are useful for correlating strata and placing them in age order
what are strata
layers of rocks
