ice ages: introduction to their profound impact on planet earth

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!