Glaciers. How Glaciers Form Form when snowfall exceeds melting. The heat and pressure from the mass...

Glaciers

How Glaciers Form• Form when snowfall

exceeds melting.• The heat and

pressure from the mass cause a slight melting which lubricates the bottom of the glacier.

• Gravity pulls it down making it flow.

Glacial Zones• Firn Line – snowline

from previous seasons (firn) that divides the glacier.

• Zone of Accumulation – colder upper portion of glacier where snowfall exceeds melting.

• Zone of Ablation – warmer lower portion of glacier where melting exceeds snowfall.

Crevasse: Formed when the glacier flows over a bump or ridge causing the brittle surface to flex and form deep cracks.

Moraines• Lateral Moraine –

rock debris on side of glacier

• Terminal Moraine – debris at end of glacier.

• Medial Moraine – debris lines formed where two glaciers meet.

Features of Glacial Landscapes

Cirque

• Bowl shaped head of an active or former glacier

Horn

• Sharply pointed mounting peak bounded by three or more cirques.

Hanging Valley

• A valley left by tributary valley where it meets a much larger glacier.

Glacial Erosion• Glaciers form giant U shaped valleys instead of

steep V shaped ones that fast flowing rivers carve.

Fjord: Narrow inlets from the ocean that were once occupied by valley glaciers.

Loess

• Fine grained glacial silt, also called rock flour.

Glacial Erratics

Boulders that are transported and deposited by a retreating glacier.

Types of Glaciers

Tropical Glaciers• Occur in the tropics in Peru, New Guinea and Africa• Appear to be disappearing fast with warming

climate

Icefield• Large area of valley glaciers that connect together.• Harding Icefield on the Kenai Peninsula is one.

Icefield at Mt Kilimanjaro, Africa

Alpine Glaciers• Form at high altitudes in places where the winter

snow does not melt.

Valley Glacier

• Flows for almost all its length in a mountain valley

• Matanuska Glacier is an example.

Outlet Glacier• A valley glacier pouring out of an icefield.• Exit Glacier is an example.

Tidewater Glacier• Has a terminus (end) at a large body of water that

constantly melts causing large chunks to fall off (calving).

Icebergs

• Break off of tidewater glaciers and continental glaciers.