Chapter 17: Glacial processes and landforms

how is a glacier different from a snow cover?

moves under its own weight and flows slowly

how does a glacier form?

layers of snow, year after year and compaction

layers of snow becoming a glacier

snow: 80% air

gradually compacts

may melt and refreeze

firn, and then

ice

zone of accumulation

snow is accumulating in part of the glacier

zone of ablation

ice is melting at the edge of the glacier

glacial advance

outer edge of ice is moving forward

glacial retreat

glacial edge melts faster than it accumulates

glacial flow

ice is flowing forward, but the outer edge isn’t necessarily changing

mountain glaciers (also alpine glaciers)

frozen rivers of ice that form in mountainous areas and flow down valleys

cirques

a bowl-like depression that serves as a source area for some alpine glaciers

continental glaciers

very large, flowing body of ice that covers a significant part of a landmass, thousands of metres thick

glacial plucking

erosional process by which glacial ice pulls rocks out of the ground

glacial erratics

large boulders that have been plucked and transported a great distance

tarn

melt left behind in cirque

Arete

ridge between cirques

horn

peak with 3 or more aretes

glacial till

sediment deposited by a glacier

moraine

ridge-like feature that forms at the front or side of a glacier

types: lateral, medial, terminal, recessional

drumlins

elongated hills of sediment formed by glacial action that indicate the direction of past ice movement

glacial outwash

sediment deposited by a glacier’s meltwater

esker

streambed confined within glacier. sediments in streambed like any other river. glacier retreats, leaves sediment ridge behind.

permafrost

any ground that remains frozen for two or more consecutive years