California
State University Long Beach
GEOL 300i; Earth Systems
and Global Change
Lecture 21a
Dr.
Rick Behl
Climate change and civilizations
-
Holocene climatic variation recorded
in Greenland ice cores & North Atlantic sediment
-
Continuation of Dansgaard-Oeschger cycles
but at lower amplitude
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Approximately 2500-2600 year cycles
-
Warm and wet, or
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Cold, dry, and windy
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8800-7800, 6100-5000, ~3950, 3100-2400,
& 600-150 yrs b.p.
Origin of Noah’s flood and Gilgamesh
legends?
-
Ryan and Pittman’s new story
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Early in the Holocene
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Black Sea was smaller, fresher lake
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Cut off from Mediterranean by the Bosphorus
Straits
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Agriculture had developed on flat, fertile
ground
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Approximately 7,500 years ago
(5500 B.C.)
-
Warmest interval of the Holocene
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Raising sea level rushed through the
Bosphorus Straits
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Flooded flat, fertile ground with salt
water
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Farming and root languages spread through
Europe and Middle East
Mesopotamia
-
2000-2200 B.C. (~4000 years ago)
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Destruction/abandonment of Akkadian
cities and civilization
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Possibly also Greece, India, Egypt,
etc. simultaneously collapsed
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Climatic cooling, increased aridity,
and windiness
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Expansion of desert areas (Sahara, etc.)
Classic Mayan civilization collapsed
(Yucatan, Mexico)
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800 A.D. (~1200 years ago)
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200 years of increased climatic dryness
(relative drought)
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Changes in relative evaporation/precipitation
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Shown by oxygen isotope values of shells
in lake core sediments
-
Driest interval of the entire middle
to late Holocene
-
Similar climatic record throughout the
Mesoamerica/Caribbean region
-
Compounded social and resource problems
Little Ice Age
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1400 A.D. to 1800’s A.D.
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Last cold stage in Holocene
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For any questions or problems with these pages contact>
John Francis
Email: jfrancis@csulb.edu
Phone: 562-985-4928
written by R. Behl.
Last changes: 18 Nov. 1997