Time and Geologic Change

GEOLOGIC CATASTROPHES - SUDDEN, DRAMATIC EVENTS

• SOME RELATED TO PLATE TECTONICS
• VOLCANIC ERUPTIONS
  • Krakatoa: 1883 - tsumani, affected climate
  • Vesuvius: 74 AD
  • Santorin/Thera: ~1500 BC - tsumani, ash
    • EXTINGUISHED MINOAN CIVILIZATION ON CRETE
    • HISTORICAL BASIS FOR EVENTS RECORDED IN EXODUS IN THE BIBLE & FOR LEGEND OF ATLANTIS
  • Mount Saint Helens: 1980
  • Laetoli, Tanzania: ~3.6 million years ago - Austalopithecus footprints preserved in ash
  • Heimaey, Iceland: 1973
• EARTHQUAKES
  • Tsunamis also
  • San Francisco: 1906
  • Alaska: Easter 1964
• FLOODS - not related to Plate Tectonics and not mentioned in text
  • Upper Mississippi valley - 1993
  • Southwest Georgia - 1994

SUBTLE GEOLOGIC EVENTS

• CLIMATE CHANGE
  • Associated with Glacial-to-Interglacial Transition
  • Fertile Crescent/Egypt: Formerly Wetter - Now Dry
• SEALEVEL CHANGE
  • Currently (1890-1950): 1.2 mm/year (120 mm/century = 12 cm/century = 4.5 inches/century)
  • Due to melting of glaciers as temperatures warm
    • TIME FOR MAXIMUM SEALEVEL RISE IF ALL GLACIAL ICE MELTED
    • 50-70 M RISE = 5,000 TO 7,000 CM RISE
      • AT CURRENT RATE -> 5,000-7,000/10 CM/CENTURY = 500-700 CENTURIES = 50,000 TO 70,000 YEARS -> NO PROBLEM (UNLESS YOU LIVE RIGHT ON THE COAST)
      • AT RATE DURING LAST DEGLACIATION (100 M RISE IN 10,000 YEARS = 10,000 CM IN 100 CENTURIES = 100 CM/CENTURY) = 5,000 TO 7,000 YEARS
    • NOTE - DURING MAXIMUM GLACIAL ADVANCE 18,000 YEARS AGO, SHORELINE LOCATED AT PRESENT 100-M DEPTH CONTOUR (NEAR CONTINENTAL SHELF EDGE)
    • NOTE 2 - NOAH'S FLOOD AND FLOOD MYTHS IN OTHER CULTURES MAY DERIVE FROM TRANSGRESSION OF SHORELINE
      • OTHER POSSIBILITY -> SUDDEN FLOODING OF CONTINENTAL SHELF AROUND BLACK SEA, WHICH IS CONNECTED TO THE MEDITERRANEAN THROUGH THE BOSPORUS AND DARDENELLES
• CRUSTAL CHANGE
  • As Ice Loads and Water Loads are Removed from or Placed on Crust, the Crust Rebounds or Subsides

HOW FAST IS FAST?

• EROSION, UPLIFT, SEALEVEL, SHORELINE PROGRADATION
  • Erosion
    • AVERAGE - 0.03 MM/YEAR
    • GRAND CANYON - 0.7 MM/YEAR
  • Uplift
    • SCANDINAVIA - 10 MM/YEAR
  • Sealevel
    • DEGLACIATION - 10 MM/YEAR
  • Shoreline Progradation
    • TIGRIS-EUPHRATES - 25,000 MM/YEAR
  • Although these rates are slow on a human time scale, they are extremely fast on a geological time scale
• WAYS TO GROW & CHANGE
  • Linear VS Nonlinear
    • UPLIFT IN CALIFORNIA (0.5 - 1.5 M/YEAR)
    • GROWTH IN HUMAN POPULATION (EXPONENTIAL)
  • Nonrepeating VS Repeating Changes
    • BOTH EXAMPLES ABOVE ARE NONREPEATING
    • TIDES, SEASONS ARE REPEATING
  • Periodic/Rhythmic VS Episodic Changes
    • TIDES, SEASONS ARE PERIODIC/RHYTHMIC
    • TURBIDITY CURRENTS, LANDSLIDES ARE EPISODIC

CATASTROPHIC VS UNIFORM VIEWS OF CHANGE

• CATASTROPHIC INITIALLY
  • Bible interpreted literally
    • EARTH YOUNG, ETC
    • GRAND CANYON - 0.7 MM/YEAR
• UNIFORM DISPLACED CATASTROPHIC IN LATE 1700'S AND EARLY 1800'S
  • normal everyday processes over long period of time
  • Strong bias against catastrophic
• TODAY - EQUILIBRIUM AMONG COMPETING PHYSICAL, CHEMICAL, BIOLOGIC PROCESSES

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