What is a glacier?
0 A large, long-lasting mass of ice which
forms on land and moves downslope
because of gravity.
What metaphors do we use
for glaciers?
0 Glaciers are often referred to as a River
of Ice or
0 Bulldozer of Ice
How do glaciers form?
How do glaciers form?
Glaciers form over many years in places
where the snowfall in winter exceeds
the snow melt in summer
Gravity pulls the ice down the hill
What are the two types of
Alpine and Continental
Alpine Glaciers
0 A.k.a. Valley Glaciers
0 form near mountain tops and slide down the valleys
0 They can be hundreds of feet thick.
Tyndall Glacier, Alaska
Aletsch Glacier, Switzerland
115 sq miles
Continental Glaciers
Continental Glaciers
0 cover large areas (Antarctica, Canada)
0 can be 2 – 3 miles thick
0 Weight of the ice depresses the ground
0 When these glaciers melt the land ‘rebounds’
0 Some areas depressed during the last ice age are still
What are the Landscape
Features of Glaciated Areas?
What are the landscape features
left by Alpine or mountain
0 Till- direct deposit of glacier; unsorted
0 Mountain shape:
0 Rugged landscapes
0 Jagged peaks
0 U-shaped valley
0 Moraine- a mass of till
Rugged Landscapes
Jagged Peaks
Northeast-looking oblique aerial photograph showing the snow-covered
summit accumulation area of Mount Fairweather, Fairweather Range,
Glacier Bay National Park, Alaska.
West-looking photograph showing an angular arete ridge, composed of
schist, on the upper Taku Glacier, Juneau Icefield, Tongass National
Forest, Coast Mountains, Alaska.
U-Shaped Valley
River Valley
Glacial Valley
0 Mass of till (unsorted sediment) left by a glacier
The u-shaped valley to the right side of the photo is the ice-free valley of
Talkeetna Glacier, Talkeetna Mountains, Alaska. Note cirque at the top of
the valley on the left.
Aletsch Glacier, Switzerland
Ground Moraine
Terminal Moraine
Mendenhall Glacier, Tongas National
What are the
characteristics left by
0 Valleys- u shaped
0 Till - unsorted sediment
0 Kettle lakes
0 Scratches and grooves
0 Drumlins
Kettle Lake
Finger Lakes
0 streams and lakes were modified by
0 Retreating glaciers deposited recessional
moraines that blocked the water flow and
created deep lakes
0 Examples
0 Seneca lake: 40 miles long, 618 feet deep
0 Cayuga: 40 miles long, 435 feet deep
NASA photo
Striations (Scratches)
Polished Rock
Form when chunks of ice ‘calve’ off the front of the glacier and land
in the water
Iceberg in Antarctica
Floating Icebergs
A Zodiak is cruising along a glacier front, showing
the tremendous size of the ice blocks
Giant Iceberg
Gentoo penguin family, Antarctica
What are the tell-tale signs
that a glacier was in the area?
0________________ valley
0________________ sediment
0________________ in bedrock
See you in class!
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