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Name the geologic eras (oldest to youngest)
Paleozoic (paleo = old), (zoic = life (think zoo)
Mesozoic (meso = middle)
Cenozoic (ceno = recent)
4500 - 542 MYA
- 4.04 BYA: oldest rock (gneiss/banded) = solid ground
- (could probably find older b/c of heavy bombardment)
single-celled life (no nucleus) = first fossils
first/small shelly organisms
Earth formed 4.54 BYA
- Main Things:
- - before shells and hard parts like bones (nothing hard to fossilize)
- - single-celled life (squishy stuff)
- - biggest chunk of Earth's history (like, 11%), most unknown
542 - 251 MYA
first vertebrates (primitive fish)
first land plants
first amphibians on land
- Main Thing:- a lot of firsts (fish, plants, insects, reptiles appear)
251 MYA - 65 MYA
first dinosaur (Nyasaurus Parringtoni)
first mammal (Eozostrodon)
oldest flowering plant
- 65 MYA: meteorite strikes Yukatan = dino extinction
- Main Things:- dinosaurs
- - first flowering plants
From 65 MYA onward
diversification, grazing animals, trees, large predators
- Main Thing:
- early on, large predators
- later, grassland, familiar plants and animals
What do scientists use to identify eras?
Relationship between eon, era, and period
Eons are made up of eras, and eras are made up of periods.
Scientific approach Geologists use
Observe --> Pattern --> Tentative Hypothesis --> Confirmation
- 1.) Observe geologic features
- 2.) Develop hypotheses (explanation) - why?
- 3.) Test
Two Key Assumptions used to determine Geologic history
1.) Evidence (features) preserved in geologic records (rocks) are an accurate picture of prehistoric events (accurate, not complete).
2.) Physical, chemical, and biological processes operating today have operated in the same way in the past (laws of nature haven't changed).
The three ~ISMs
- 1.) Gradualism - Inductive Reasoning
- - James Hutton (farmer, guy that no one understood)
- - proposed all geologic processes happen slowly
- 2.) Catastrophism - Inductive
- - Georges Cuvier (paleontologist)
- - proposed fast, catastrophic events happened (extinction)
- 3.) Uniformitarianism - Deductive
- - Charles Lyell (lawyer, douchebag)
- - against Catastrophism (wanted to throw TP all over Cuvier after taking a dump on his ideas), but supported "Steady-State Earth" idea (shit never changes, duh Cuvier)
4 Principles of Uniformitarianism
- 1.) Uniformity of Natural Laws
- - things in nature never change
- 2.) Uniformity of Natural Processes
- - scientific processes never change
- 3.) Uniformity of Slow Rates
- - things happen slowly over time, and don't change
- 4.) Uniformity of Configuration
- - nothing catastrophic happens!
Actualism and how it relates to Uniformitarianism
In a way, it is today's Uniformitarianism
While natural laws have been constant, rates
of change have varied through time
- Actualism: The present is A key to the past.
- Uniformitarianism: The present is THE to the past.
How rates vary through time
- 1.) Rate of movement
- - sedimentation
- - plate movement
- - erosion
- - precipitation
- 2.) Rate of Occurrence
- - volcanoes, tides, earthquakes, mass extinction, glacial/interglacial periods, supercontinents, meteorite impacts
- Processes may be repeating (seasons, tides) or nonrepeating (mass extinctions).
- - rocks can be removed/created at various rates
- - rocks can record repeating/nonrepeating events