Unit 1: Land and Water Forms Glaciers as Agents of Erosion World Geography Unit 1: Land and Water Forms Glaciers as Agents of Erosion

Glaciers

What Are Glaciers? Glacier: Large sheet of ice that flows like a river under the influence of gravity. Today 1/10 of Earth’s land surface is covered by ice 10000 years ago it was nearly 1/3 Thus ice has had a huge impact on the physical world we see today

Types of Glaciers The glaciers that we see today are of two different types. Alpine Glaciers: Glaciers that form high in mountain valleys above the snowline. Continental Glaciers: Large sheets of ice that cover portions of the continental land mass.

The Last Ice Age

The Last Ice Age

Ice Cover Today

How Do Glaciers Grow? Glaciers can be seen as an open system Input – Snow Output – Ice, meltwater, and water vapor At its upper end the glacier is fed by snow this area is known as the accumulation zone If a Glacier receives more input than it looses in output the glacier grows. Accumulation Zone: where a glacier grows Ablation Zone: Where a glacier looses mass

How Does a Glacier Move? The movement of a glacier has much to do with the properties of the ice that makes up the glacier At different depths glacial ice has different properties, and behaves in different ways At the top it is solid, much like ice in a freezer, however deep within the glacier the ice is plastic, more like a frozen jelly This plastic ice distorts itself, and flows in response to the upper layers of ice, and the slope of the land

Glacial Mass and Balance

Evidence of Movement 1.4.2 Examine evidence for the direction of movement of a continental glacier. (a)

Depositional Glacier Terms The following is a list of terms that are useful in talking about glaciers Till Outwash plain Terminal Moraine Erratic Drumlin Esker 1.4.1 Define the terms outwash plain, terminal moraine, erratic, drumlin, and esker. (k)

Till Till: Direct ice deposits that appear unstratified and unsorted; a specific form of glacial drift

Outwash Plain Outwash plain: Glacial stream deposits of stratified drift or melt-water fed, braided and overloaded streams; occurs beyond a glaciers moraine deposits.

Terminal Moraine Terminal Moraine: Eroded debris that is dropped at a glacier’s farthest extent; forming a ridge like structure

Erratic Erratic: a piece of rock that deviates from the size and type of rock native to the area in which it rests. These rock are carried by glaciers and deposited when they melt.

Erratic A piece of rock that is left behind by a glacier, that is obviously not like the surrounding rocks. As glaciers move they pick up large chunks of rock, as they melt the rocks are left behind.

Drumlin Drumlin: A depositional landform related to glaciation that is composed of till (unstratifeid, unsorted eroded material) and is streamlined in the direction of continental ice movement; blunt end upstream and tapered end down stream with a rounded top.

Drumlin

Esker Esker: A curving, snakelike, narrow deposit of coarse gravel that forms along a melt-water stream channel developing in a tunnel beneath a glacier.

Esker

Erosional Landforms Alpine glaciers create spectacular, dramatic landforms that bring to mind the Canadian Rockies. Some of these features include; Cirque Arête U-Shaped valley Hanging valley Lateral moraine Terminal Moraine Medial Moraine Col Horn Define the terms cirque, arête, hanging valley, lateral moraine, and terminal moraine. (k)

Cirque Cirque: A scooped-out, amphitheater-shaped basin at the head of an alpine glacier valley.

Arête Arête: A sharp ridge that divides two cirque basin. Derived from “knife edge” in French, these form sawtooth and serrated ridges in glaciated mountains.

U-Shaped Valley U-Shaped Valley: Large deep valley created by the main glacier in a flow gouging down deep into the bedrock

Hanging Valley Hanging Valley: Like a tributary to a river a hanging valley consists of a smaller ice flow that runs into the main glacier. It gets its name because it does not carve as deep into the ground, resulting in a valley at a higher altitude

Terminal or End Moraine Terminal moraine: Eroded debris that is dropped at a glacier’s farthest extent

Lateral Moraine Lateral Moraine: Debris transported by a glacier that accumulates along the sides of the glacier and is deposited along the margins.

Medial Moraine Medial Moraine: Debris transported by a glacier that accumulates down the middle of the glacier, resulting from two glaciers merging their lateral moraines.

Col Col: Formed by two headward eroding cirques that reduce and arête to form a high pass or saddle-like narrow depression.

Horn Horn: A pyramidal, sharp-pointed peak that results when several cirque glaciers gourge an individual mounatin summit from all sides

Glacial Striations Glacial striations or glacial grooves: scratches or gouges cut into bedrock by process of glacial abrasion. Glacial striations usually occur as multiple straight, parallel grooves representing the movement of the sediment-loaded base of the glacier.

Glacial Striations

Kettle Lakes Kettle Lakes: Forms when an isolated block of ice persists in a ground moraine, an outwash plain, or valley floor after a glacier retreats; as the block finally melts, it leaves behind a steep sided hole that frequently fills with melt water

Kettle Lakes

Fjords Fjord: A drowned glacial valley near the coastline Formation A large glacier cuts away at the continental shelf Striping down the land Carving a large U shaped valley When the Glacier melts seawater floods the valley

Continental Vs Alpine Use the sheet “Features of Alpine Glaciation and Continental Glaciation Compared” and the notes from your class to complete the worksheet.