glac2

Glaciers and Climate Change (Ch. 14)

Glacial deposits: till and stratified drift

Till: transported and deposited by ice: poorly sorted and not rounded

Landforms composed of till:

Ground moraine: till deposited underneath glacier.

Drumlins: till reshaped into elongated hills

Moraines:

Lateral: at edges
Medial: formed when two glaciers join
End: at front of glacier

Stratified drift: deposited by water, sorted and layered
Landforms composed of stratified drift:

Kames (round hills) and Eskers (sinuous ridges): deposited in meltwater tunnels
Outwash: Stream-deposited sediment
Kettle: depression formed by melting of ice blocks

Last glacial age peaked 20,000 years ago, covered 30% of earth

Indirect Effects:

pluvial lakes: from higher rainfall, lower T. Example: Lake Bonneville
large quantities of meltwater filled lakes, streams

catastrophic floods Example: Channeled Scablands

Sea Level was 130 m lower

As sea-level rose: glacial valleys were drowned, creating fjords

Previous Glacial Ages have occurred ~ every 100,000 years for 600,000 years

When dinosaurs lived, the earth was up to 15°F warmer than today.

Why does the earth’s temperature change?

Milankovitch theory: variations in the Earth’s orbit and tilt affect solar radiation
Tectonics (position of continents)
Changes in the atmosphere

volcanoes or meteorite impacts could increase dust and sulfates, cool Earth
Greenhouse Effect: gases in atmosphere keep Earth warm

Global Warming
Humans have added CO₂ (and other gases) to the atmosphere by burning coal and oil.
Global temperatures has risen 0.5 to 1° F
Sea level has risen 4 to 10 inches
Difficulty: separating effects due to CO₂ from natural climate trends

Predictions for 2100:
2 to 6°F temperature increase
6 to 38 inch sea-level increase

Impacts:
severe weather (heat waves, hurricanes, floods, droughts)
flooding of coastal areas, saltwater intrusion
ecological: shift in habitats

Over the next few centuries?
1 to 5% chance that W. Antarctic Ice Sheet becomes unstable, raise sea-level 20 feet