GEOLOGISTS DEAL WITH IMMENSE SPANS OF TIME, TYPICALLY OF THE ORDER OF THOUSANDS TO MILLIONS TO BILLIONS OF YEARS (Dott and Prothero, 1994)
GEOLOGIC & RELATED EVENTS
(1) Short-term (instantaneous)
Volcanoes
Earthquakes
Tsunamis (Tidal Waves)
Asteroid Impact
Extinctions (catastrophic)
(2) Long-term (thousands to millions of years)
Glaciers
Rise of Mountain Ranges
Opening of Ocean Basins
Movement of Lithospheric Plates
Evolution
Extinctions (non-catastrophic)
GEOLOGIC EVENTS CAN BE:
(a) Dramatic (readily observable)
(b) Subtle (not detected over short periods of time)
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SUBTLE GEOLOGIC EVENTS (slow geologic changes) |
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Average erosion of continent |
0.03 mm/year |
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Cutting of the Grand Canyon since 5 Ma |
0.7 mm/year |
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Postglacial rise of sea level (100 m over last 20,000 yrs.) |
5 mm/year |
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Rise (rebound) of Scandinavia |
10 mm/year |
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Slow spreading ridge (opening Atlantic since 170 Ma) |
10-50 mm/year |
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Fast spreading ridge (opening of Pacific since 190 Ma) |
90-180 mm/year |
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Advance of Tigris-Euphrates delta |
25,000 mm/year |
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DRAMATIC EVENTS: Volcanic eruptions, earthquakes, tsunamis, etc.
LINEAR CHANGE occurs at a constant rate whereas NONLINEAR CHANGE does not.
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LINEAR CHANGE (rare in nature) |
NONLINEAR CHANGE |
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Regional uplift of land masses (measured over several tens of thousands of years). |
Regional uplift (measured over millions of years) |
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Seafloor spreading (measured over tens of thousands of years) |
Seafloor spreading (measured over millions of years) |
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Growth of human population (measured over hundreds of years) |
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Sea level (measured over hundreds of years) |
Sea level (measured over thousands of years) |
REPEATING CHANGES can be PERIODIC (RHYTHMIC) or EPISODIC.
