8.3 Glaciers

Types of glaciers

AlpineSmall glaciers that form valleys

Ice sheetsEnormous glaciers that can cover entire continents

Glacier FormationDescribe the steps

Thick, dense compacted snowFirn:

Firn compacts into glacial iceGlacial ice:

Advancing: A glacier growing faster than it is melting

Retreating: A glacier melting (receding) at the leading edge faster than its growing. It’s NOT traveling backwards.

Glacier Movements

Plastic Flow

Deep within, there is a huge amount of pressure due to weight of ice pressing down.

50 meters thick of ice creates enough pressure to cause ice to flow through the center of a glacier very slowly.

Describe:

Glacier Movements

Basal Slip

Water beneath glacier acts as a lubricant, so entire glacier can slide. This movement can cause a large crevasse (crack), to form.

Describe:

Rate of movement:

Typically a few meters/ day, but can have faster surges.

Glacial structures from erosionStriation

Long scratch marks found in rocks due abrasion caused by rocks & gravel dragged by glacial movement.

Describe:

U-Shaped ValleysV-shaped valleys that are widened by glaciers.Describe:

Glacial structures from erosionHorn peaks

When several cirques converge, the part that is not cut out looks like a horn sticking out of the ground.

Describe:

Cirques

Valleys that look like giant armchairs because they have 3 steep sides & one open side.

Describe:

Glacial structures from erosionFjords

Very steep inlets to the ocean.Describe:

Roche moutonnees

Landforms w/ 1 rough side & 1 side that has been abraded smooth.

Describe:

The coarsely graded sediment deposited by glaciersDescribe:

Till

Unsorted glacial sedimentDescribe:

Glacial Drift

Big rocks deposited by a glacier into an area w/ a different type of rock.

Describe:

MorrainesPiles of boulders, rocks, pebbles, & clay left behind by a glacier.

Describe:

Structures FormedGlacial Erratics

form at the edge of glaciers.Describe:

DrumlinsSmooth, egg-shaped hills left behind by continental ice sheets.

Describe:

Structures FormedTerminal Moraines

Deposits left by melted water coming off a glacier.Define:

kettlesWhen large blocks of ice get trapped under stratified drift, the ice melts and leaves large holes.

Describe:

Stratified Drift

Structures Formed:

Describe: Winding ridges of sand & gravel left behind by receding glaciers.

Eskers

Earth’s OrbitChange in Earth’s orbit around the sun cause slight temperature variations.

Effects:

Effects: The tilt of Earth’s axis changes over time & can affect the amount of sunlight reaching different parts of earth.

Precession

Current ice age theory Changes in the Earth’s axis of rotation can work together to alter the temperatures. This is thought to lead to the formation of large glaciers & put Earth into ice ages.

Explain:

2 million years ago, & peaked 20,000 years ago.Last ice age