GLACIERS

Formation

Snow accumulation

More winter snowfall than summer melt

Glacier formation is similar to sedimentary rock formation

Types of Glaciers Valley glaciers or alpine

glaciation Ice sheets or continental

glaciation

Glaciers of the world

85% of glacier ice in Antarctica 10% of glacier ice in Greenland Alpine glaciers comprise only 5%

of world’s glacier ice

Alpine Glaciers

Form in valleys Gravity causes glacier movement Glaciers flow from higher to lower

elevation

Alpine Glacier Flow Velocity Overall downward flow velocity ranges from

a few millimeters to 15 meters per day Glaciers in warmer climate flow more

quickly Central part moves faster than sides Surface moves faster than base

Glacier movement Basal sliding Plastic flow Brittle/Rigid Zone

Continental Glaciers Cover a large part of a continent Gravity causes glacier movement Glaciers flow downward and outward

from a central high point Plastic flow more common than basal

sliding

Arctic Sea Ice Fresh water, like glaciers, but do not flow

like glaciers

And resulting landscapes

Glacial Erosion

Erosion Glacier movement erodes the bedrock

underneath the glacier and can drastically change the landscape Plucking Abrasion Polishing Striations

Erratics &Striations

Alpine landscape features

Continental landscape features All the sediment that a glacier picks up is

deposited as unsorted and unlayered rock debris called “till”

Most features are created during glacial retreat

Effects on North America

Ice Ages

Glacial Ages

A period of long-term reduction in Earth’s temperature, resulting in the presence of continental and polar ice sheets and alpine glaciers Glacial periods Interglacials

The last glacial period ended 10,000 years ago

Glacial Extent of Last Glacial Period ice_age.mov

Laurentide Ice Sheet

Stevens Point is located right beyond the recessional moraine—in outwash plain

Glacial Erosion in Wisconsin

Whitewater Wisconsin Map Activity

Topographic Maps

Topographic maps