Chapter 18 Glaciers & Glaciation

Glaciers Mass of ice forming when more snow/ice is deposited in fall/winter than is melted in spring/summer

Glacial Ice

Types of Glaciers Valley/Alpine Glaciers Mountains Migrate downslope

Types of Glaciers Ice Sheets/Continental Glaciers Larger than valley glaciers Move in all directions 2 Major Ice Sheets (Greenland & Antarctica)

What if all the ice melted? Antarctic ice sheet 80% of the world’s ice 2/3 of Earth’s fresh water ~ 1.5 times the area of the US Sea level would rise ~70 meters

Sea level and Glacial Ice

The Glacial Budget Figure 18.11

Glacial Deposits Glacial Drift – all sediments of glacial origin Till – material deposited directly by ice Stratified Drift – deposited by meltwater

Till usually Unstratified & Unsorted Figure 18.19

Glacial Deposits Landforms made of till Moraines – layers or ridges of till Lateral Recessional Terminal or End

Lateral Moraine – Alpine Glaciers

Glacial Deposits Figure 18.25

Moraines of Long Island

Glacial Deposits Outwash Plains Flat with mild slopes Form from meltwater deposits Occurs beyond moraine

Glaciers of the past Four major stages in North America During peak ~ 30% of earth was covered Nebraskan (ended ~ 1.6 mya) Kansan (ended ~ 690,000 ya) Illinoian (ended ~ 125,000 ya) Wisconsinan (ended ~ 10,000 ya)

Maximum extent of ice during the Ice Age Figure 18.27

Current Glacial Ice Covers ~ 10% of earth’s surface Antarctic ~ 85% Greenland ~ 10% Scattered ~ 5%

Current Glacial Coverage

Impacts of Glaciers Migration of animals & plants Crustal rebounding of the crust Changes in sea level Climatic changes

Causes of Glaciation Plate Tectonics Continents in different areas in the past Changes in oceanic circulation

Shape of Earth’s orbit varies Causes of Glaciation Milankovitch Hypothesis Shape of Earth’s orbit varies Angle of Earth’s axis changes Earth’s axis wobbles (precession)

Milankovitch Hypothesis

End of Chapter 18