Chapter - 8. Section – 8.3 Glaciers. Objectives. Explain how glaciers form. Compare and contrast the conditions that produce valley glaciers with those that produce continental glaciers. Describe how glaciers modify landscapes. Recognize glacial features.
Section – 8.3
Explain how glaciers form.
Compare and contrast the conditions that produce valley glaciers with those that produce continental glaciers.
Describe how glaciers modify landscapes.
Recognize glacial features.
latitude: distance in degrees north and south of the equator
A large, moving mass of ice is called a glacier.
Glaciers form near Earth’s poles and in mountainous areas at high elevations. They cover about 10 percent of Earth’s surface.
Glaciers that form in valleys in high, mountainous areas are called valley glaciers.
As valley glaciers flow downslope, they carve V-shaped stream valleys into U-shaped glacial valleys.
Glaciers that cover broad, continent-sized areas are called continental glaciers.
These glaciers form in cold climates where snow accumulates over many years.
Both valley glaciers and continental glaciers move outward when snow gathers at the zone of accumulation, a location in which more snow falls than melts, evaporates, or sublimates.
At the high elevations where snow accumulates, valley glaciers scoop out deep depressions, called cirques.
When there are glaciers on three or more sides of a mountaintop, the carving action creates a steep, pyramid-shaped peak, called a horn.
Hanging valleys are formed by valley glaciers when tributary glaciers converge with the primary glaciers and later retreat.
A valley is left hanging high above the primary valley floor.
Glacial till is the unsorted rock, gravel, sand, and clay that glaciers carry embedded in their ice and on their tops, sides, and front edges.
Glaciers deposit unsorted ridges of till called moraines when the glacier retreats.
When the farthest ends of a glacier melt, meltwater floods the valley below. Outwash is the gravel, sand, and fine silt sediment that is deposited by meltwater carried away from the glacier.
Drumlins, eskers, and kames
Continental glaciers that move over older moraines form the material into elongated landforms called drumlins.
Drumlins, eskers, and kames
Streams flowing under melting glaciers leave long, winding ridges of layered sediments called eskers.
Kettles, or kettle lakes, form when water from runoff or precipitation fills a hole that formed when a large block of ice broke off a continental glacier and melted.
Glaciers modify landscapes by eroding and depositing rocks.
Glaciers are large moving masses of ice that form near Earth’s poles and in mountain areas.
Glaciers can be classified as valley glaciers and continental glaciers.
Features formed by glaciers include U – shaped valleys, hanging valleys, moraines, drumlins, and kettles.