Glacial Landforms. Continental Glaciers Striations Erosion of soil.

Glacial Landforms

Continental Glaciers

Striations

Erosion of soil

Roches Moutonnees

or sheepback

• Weslemkoon Lake, Ontario

• Roche Moutonnee By The Lake

Moraines

Glacier Flow

Terminal Moraine

Material carried in the glacier like a conveyor belt is piled up in front of the ice sheet to form a moraine.

The larger the moraine the longer the glacier is stationary, ie., in a state of mass balance.

This material is till and is largely unsorted (ie., it is all mixed up with different sizes).

Terminal moraines mark the maximum extent of ice advance.

Glacier Flow

Terminal moraine

If the climate changes and becomes warmer, the glacier will retreat and eventually achieve a new state of mass balance.

Glacier Flow

Terminal moraine

If the climate changes and becomes warmer, the glacier will retreat and eventually achieve a new state of mass balance.

Note that even though the glacier is retreating, it is still flowing forward.

It is just being ablated (melted) faster than it flows.

Glacier Flow

When the new state of mass balance is reached, a new moraine is created, called a recessional moraine.

For the skiers: Horseshoe Valley and Mt. St. Louis-Moonstone are on a recessional moraine.

Terminal moraine

Recessional Moraine

Sometimes two lobes of glacial ice come together and a moraine forms between them

This happened north of Lake Ontario when there was a pause and short re-advance of the ice age during the last retreat – the ice lobe left in what would eventually become Lake Ontario grew north (and east and west and south) and met the main sheet moving south – they met just north of Toronto - the Oak Ridges Moraine – called interlobate moraine

Remnant ice sheet or chunk.

“future” Lake Ontario basin

Main ice sheet to the north

The ice sheets in retreat … there is a pause ...

Main ice sheet to the north

“future” Lake Ontario basin

…. and then a re-advance of the ice for a period of time

Main ice sheet to the north

“future” Lake Ontario basin

…. and then a re-advance of the ice for a period of time

Oak Ridges - Interlobate Moraine

Lake Ontario

Oak Ridges - Interlobate Moraine

Toronto Kingston

Finger Lakes

Drumlins are egg-shaped hills oriented to the direction of ice movement – usually in clusters or field – about 200/300 in S. Ontario near Peterborough.

Direction of ice movement

200 - 1000 m

30-100 m

Steep face indicates direction ice came from.

Drumlin

http://www.sfu.ca/~tabrenna/students/tim/tim.htm

http://www.virtualsk.com/maps/ecoregions_3.html

Rivers flowing under the ice sheet in tunnels carry a lot of sediment – some of the material gets deposited on the bottom of the tunnel – when the ice melted the long often windy pile of material is left – called an esker – because the flowing water tended to carry away the finer particles eskers are made of many sand and gravel and have been exploited for the aggregate industry.

The flowing water of the melt water streams selectively sorted the sediments – finer particles laid down in lakes whereas coarser particles were left in rivers.

http://www.homepage.montana.edu/~geol445/hyperglac/meltwater1/ESKERS.htm

Erratics

Spillway with a Mistfit stream

Glacial Ponding

When the ice sheets started to melt about 15,000 years ago, huge amounts of water poured off the ice and large lakes were created in front of the sheets – huge quantities of sediment were deposited in these lakes (called glacial ponds) – today they are large flat areas and have fertile soils – called lake plains – eg., Great Lakes Lowlands; southern Manitoba (Lake Aggasiz) and part of the Niagara Fruit Belt.

Glacial Ponding

Sediments get depositedWeight of ice depresses the land

As the ice begins to melt, meltwater collects in front of the ice.This is called glacial ponding

Glacial Ponding

Sediments

The ice age ends and the ice sheets retreat.

Glacial Ponding

Sediments

The ice age ends and the ice sheets retreat.

SedimentsWhen ice retreats, land rebounds

Glacial ponding drains away

SedimentsWhen ice retreats, land rebounds

Sediments remain behind and make for excellent soil.Called lake plains.

In some areas the ocean flooded inland quite a way during the period of ice retreat because the land was depressed from the weight of the ice – also created fertile areas, eg., St. Lawrence River valley lowlands – sand bars, etc. left behind.

Deranged Drainage

Pattern

Alpine Glaciers

Cirque

Arete

Tarn

Col

Horn

Cirques, Aretes, U-shaped valley, Horns

Cirque

Arete

Col

Horn

Tarns

V- Shaped Valley

U-Shaped

Valley

This is a Fjord!

The formation of a Hanging Valley.

Glaciers

Sea level change and glacial lakes

Video – New York City goes under

Video – Climate Change

Glaciers

Take the quiz and see how much you know about glaciers

Video – Geography Glacier Quiz

The End!