Ice Ages: Introduction to their Profound Impact on Planet
Earth
Glaciers
1. Climatic Setting Ice Ages
2. Indirect Effects of Glaciers
1. Climatic Setting of Glaciers
Colder
Warmer
Gradual Cooling into
the Pleistocene - cause under
debate
In the Pleistocene
Varves
But in last few centuries, changes in solar output caused the Little Ice
Age and warming up since
Is it natural warming from the Little Ice
Age? Or human-caused global
warming?
Explored later in this class
2. Indirect Effects of Glaciers
Water moves backand forth between
glaciers and oceans
• “Noah’s Flood” hypothesis
• William Ryan & Walter Pittman (Columbia
• Controversial, not universally accepted, but intriguing
• Coming out of last ice age ~7600 years ago (=5600 B.C.), sea level was low but rising– Why?
• Black Sea was freshwater, surrounded by farms
Noah’s Flood?• Rising global sea level raised
Mediterranean above the Bosporus Strait– Broke through natural dam– Water rose ~6 inches / day– Flooded lakeshore communities
some of the evidence
• Many cultures have a flood story, many can be traced to the Black Sea area
• Remains of houses & villages have been found on the pre-flood lakeshore
• But: New work finds no evidence for a sudden rise in water level of Black Sea.
2. Indirect Effects of Glaciers:glacial loess
Loess in Alaska
Loess in Alaska
Loess Plateau, China
from glacial dust and
desert dust
2. Indirect Effects of Glaciers:paleolakes from changes in
climate patterns
2 shorelines of ancient lakes
2. Many more indirect effects!