Glaciers

Erratic

(deposition) A boulder or cobble that was picked up by a glacier and deposited hundreds of kilometers away from the outcrop from which it detached.

Out-wash plain

(deposition) A broad area of gravel and sandbars deposited by a braided stream network, fed by the melt water of glacier

Esker

(deposition) A ridge of sorted sand and gravel that snakes across a ground moraine; the sediment of an esker was deposited in sub glacial melt water tunnels

Drumlin

(deposition) A streamlined, elongate hill formed when glacier overrides glacial till.

Kettle hole

(deposition) a circular depression in the ground made when a block of ice calves off the toe of a glacier, becomes buried by till, and later melts.

Moraine

(deposition) a sediment pile of debris carried by or left by glaciers

Glaciomarine deltas

(deposition) top set is a braided stream and fore set is avalanche in water

Glacial till

(deposition, transportation) Sediment transported by flowing ice and deposited beneath a glacier or at its toe

Cirque

(erosion) A bowl shaped-shaped depression carved by a glacier on the side of a mountain

Hanging valley

(erosion) A glacially carved tributary valley whose floor lies at a higher elevation than the floor of the trunk valley

Roche Mountonee

(erosion) A glacially eroded hill that becomes elongate in the direction of flow and asymmetric; glacial rasping smoothes the upstream part of the hill into a gentle slope, while glacial plucking erodes downstream into a steep slope.

U-shaped valley

(erosion) A steep-walled valley shaped by glacial erosion into the form of a U

Tarn

(erosion) a lake that forms at the base of a cirque on a glacially eroded mountain

Horn

(erosion) a pointed mountain peak surrounded by at least three cirques

Arete

(erosion) a residual knife-edge ridge of rock that separates two adjacent cirques

Glacier

A mass of ice that moves over land (or water) under its own weight through the action of gravity . Survive the summer melt.

Zone of ablation

Ablation is subtracted.

Glacier erosion

Alpine glaciation sharpens the landscape. Smooths landscapes. Hanging valley, horn, tarn, arete, cirque, U-shaped valley, rouche mountonee

How do glaciers move in a temperate area?

Basal sliding. Liquid water or water saturated slurry layer holds the glacial ice above bedrock and thereby decreases friction. The glacier glides along on a wet cushion. Moves on base.

Glacier equilibrium

Boundary between the zone of accumulation and zone of ablation

Firn

Compacted granular ice (derived from snow) that forms where snow is deeply buried; if buried more deeply, it turns into glacial ice

What are the two types of glaciers?

Continental and mountain/alpine

Isostatic depression (weight of ice)

Continental glaciation where permanent ice places pressure on earths crust, depressing it with its weight. Causing it to subside, and melting leads to rebound. Since continental ice sheets store water, glacial growth or melting affects sea level. Land beyond an ice sheet may be covered with permafrost (permanently frozen) and pluvial lakes (flooded interior basin)

Compare and contrast the effects of alpine glaciation and continental glaciation

Continental: formed during ice ages, flow over unconfined large areas.Kettle Lakes, Outwash Plains, Drumlins. Antarctica and Greenland. Alpine: flow in mountain valleys from low to high elevations. U-Shaped Valleys, Hanging Valleys, Cirques, and Aretes. Alaska, New Zealand.

How do glaciers affect landscape?

Erosion, deposition, transportation. A glaciers weight and movement can drastically reshape landscape. The ice erodes the land surface and carries the broken rocks and soil debris far from their original places, resulting in some interesting glacial land forms.

Mountain/alpine glacier

Exist in or adjacent to mountainous regions. Limited extent. Flow from valleys, through mountains.

Glacier deposition

Glaciers can carry sediment of any size and like a conveyer belt, transport it in the direction of flow. Sediment either falls onto the surface of the glacier from bordering cliffs or gets plucked and lifted from the substrate and is incorporated into the moving ice. The sediment produces land forms, fills topographic lows. Moraine, kettle, esker, out wash plains, till, erratic, deltas, drumlin

How do glaciers move in a polar area?

Ice goes all the way down to great depths, 60 meters. The ice moves inside of the ice sheets as individual ice crystals are sliding off of each other. Internal deformation: stretching inside. New grains grow as old ones disappear

Loess

Layers of fine-grained sediments deposited from the wind; large deposits of it formed from fine grained glacial sediment blown off outwash plains

How do geologists use glacial deposits to understand the glacial history of a region?

Milankovic cycles: Climate cycles that occur over tens to hundreds of thousands of years because of changes in earths orbit and tilt. These tell when a glacial advance is triggered. Can look at the deposits and determine where they may have come from and how old they are.

Polar (frozen based) glaciers

Occurs in regions where atmospheric temperatures stay so cold all year long that the glacial ice remains below melting temp. throughout the year

Temperate (wet based) glaciers

Regions where atmospheric temps become warm enough for the glacial ice to be at or near its melting temp during part or all of the year

Ablation

Removed of ice by sublimation, melting, and calving.

Zone of accumulation

Snowfall is added to the glacier

Snow line

The boundary above which snow remains all year

Glacial advance

The forward movement of a glacier's toe when the rate of snow (accumulation) exceeds the ablation. Ice age. Glacial ice moves like a conveyer belt.

Glacial retreat

The movement of a glacier's toe back toward the glacier's origin; glacial retreat occurs if the rate of ablation exceeds the rate of supply. (Ice is melting faster that can be replaced by flow) But will not move backwards, because it cannot move against gravity.

Glacial plucking

The process by which a glacier breaks off and carries away fragments of bedrock.

Glacial rebound

The process by which the surface of continents rises back up after and overlying continental ice sheet melts away and the weight of the ice is removed.

Glacial subsidence

The sinking of the surface of a continent caused by the weight of an overlying glacial sheet

Continental glacier

Vast ice sheets that spread over thousands of square kilometers of continental crust

Glacier transportation

When ice melts, it deposits unsorted till. Melt water streams and wind transport sort the sediment to form out-wash plain gravels and loess deposits.

Glacial drift

sediment deposited in glacial environments