Glaciers Chapter 15

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Striations

"Scratch" marks left by the glaciers path

How do glaciers form

1. Snow falls and accumulates 2. Snow becomes buried and compressed 3. Snow recrystallizes into firn (rough, granular ice) 4. Firn packs into layers of ice 5. Weight of snow and ice mass causes glacier to flow

Moraine Dammed Lakes

A lake found at higher elevation that is blocked from draining by a moraine

Kame

A mound of sediment accumulated in a glacier then deposited by a melting glacier

Lateral Moraines

Are moraines that run parallel to the glacier and run the whole length of the glacier

Basal Slip Movement

At base of glacier, increased weight causes ice to melt Can stay as water Can refreeze into slush with sand and gravel This decreases friction and glacier can flow Only the Base Moves No melt when very cold

2 mechanisms for glacial movement

Basal Slip Plastic Flow

Drift

Deposits of eroded rock that is left behind by receding glaciers

How do Glaciers move

Due to their own weight and force of gravity They erode rock as they move Rate of movements varies: cm/day to m/day

Jakobshavn Isbrae

Fastest glacier in the world 4.16 mi/yr in 1985 3.54 mi/yr in 1992 5.84 mi/yr in 2000 7.83 mi/yr in 2003

Horn

Glaciers carve out the base of the mountain leaving a pointed peak

Plastic Flow Movement

Grains of ice change shape from spherical to flat Ice Grains slip over each other, propelling the glacier not touching the ground

Drumlin

Hills that are formed when a glacier travels over a previous moraine

Terminal Moraine

Is a moraine that is perpendicular to the glacial flow and it marks the furthest advancement of the glacier

Kettle pond

Kettle formed when the depression is lower than the water table 1. Glacial chunk of ice deposited 2. Ice becomes buried 3. Ice melts into a depression and water table rises

Esker

Long, winding ridge of till

Snowline

Lowest elevation where permanent snow exists

Outwash

Materials deposited and sorted evenly by glacial melt - water

Cirque

Semi-circular basin where a glacier began

Continental Glacier

Snow accumulates over a large area at high altitudes circular or oval shape moves outwards Covers continents 1000's of meters thick

What parts of the glacier move the slowest

The bottom and sides

2 types of glaciers

Valley Continental

Calving

When chunks of a continental glacier break off and fall into the ocean

Erratic

a boulder carried by a glacier

Tarn

a glacially formed lake

Glacier

a large mass of compacted snow and ice that may move due to gravity

Moraine

an accumulation of till

Crevasse

cracks in the glacier due to its movement

When does the Glacier move fastest

during warm periods and after lots of snowfall

Where does the glacier move the fastest

on a steep slope or in the middle or center of the glacier

Valley Glacier

snow accumulates at high peaks high altitudes river like shape moves downhill up to 100km long 100's of meters thick

Ice Front

the end of the glacier

How does the snow line depending on latitude

the higher the latitude, the lower the snow line

Till

unsorted rock deposited by a melting glacier


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