Geologic Time

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Author:
DrGirlfriend
ID:
256557
Filename:
Geologic Time
Updated:
2014-02-09 14:40:35
Tags:
Earth History Geology
Folders:
Geology 1020
Description:
Geologic eras in Earth's history
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  1. Name the geologic eras (oldest to youngest)
    Precambrian

    Paleozoic (paleo = old), (zoic = life (think zoo)

    Mesozoic (meso = middle)

    Cenozoic (ceno = recent)
  2. Precambrian Eon
    4500 - 542 MYA

    • 4.04 BYA: oldest rock (gneiss/banded) = solid ground
    • (could probably find older b/c of heavy bombardment)

    3.5 BYA: single-celled life (no nucleus) = first fossils

    600 MYA: first/small shelly organisms


    • 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

    Earth formed 4.54 BYA
  3. Paleozoic
    542 - 251 MYA

    500 MYA:
    first vertebrates (primitive fish)

    425 MYA: first land plants

    380 MYA: first amphibians on land

    • Main Thing:
    • - a lot of firsts (fish, plants, insects, reptiles appear)
  4. Mesozoic
    251 MYA - 65 MYA

    240 MYA:
     first dinosaur (Nyasaurus Parringtoni)

    210 MYA: first mammal (Eozostrodon)

    125 MYA: oldest flowering plant

    • 65 MYA: meteorite strikes Yukatan = dino extinction
    • Main Things:
    • - dinosaurs
    • - first flowering plants
  5. Cenozoic
    From 65 MYA onward

    35 MYA: diversification, grazing animals, trees, large predators

    5 MYA: Australopithecus

    3.2 MYA: Lucy

    • Main Thing:
    • mammals
    • early on, large predators
    • later, grassland, familiar plants and animals
  6. What do scientists use to identify eras?
    Fossils
  7. Relationship between eon, era, and period
    Eons are made up of eras, and eras are made up of periods.
  8. Scientific approach Geologists use
    Inductive

    Observe --> Pattern --> Tentative Hypothesis --> Confirmation

    • 1.) Observe geologic features
    • 2.) Develop hypotheses (explanation) - why?
    • 3.) Test
  9. 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).
  10. 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)
  11. 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!
  12. Actualism and how it relates to Uniformitarianism
    In a way, it is today's Uniformitarianism

    While natural laws have been constant, rates and intensities of change have varied through time

    • Actualism: The present is A key to the past.
    • Uniformitarianism: The present is THE to the past.
  13. 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).
    • Implications:
    • - rocks can be removed/created at various rates
    • - rocks can record repeating/nonrepeating events

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