Transcript U-Shaped Valley

3 Theories of Glaciation
Orbit Change
Earth’s orbit changes gradually, turning more
elliptical over a cycle that takes 97 000 years. Midcycle is the coldest, which is the time when glaciers
form.
Axis Change
It takes over 41 000 years for the Earth to change the
tilt of its axis. The North Pole receives less light, the
temperature drops, and glacial ice begins
accumulating
Blocked Sun
The sun gets blocked by dust in the atmosphere
caused by volcanoes or giant asteroids. This
prolonged cooling causes and ice age to occur.
Types of Glaciers
Alpine Glaciers
These glaciers move from mountains to lowland areas
following river valleys. Tributary glaciers flow into a
single main river of ice, where the sides and bottom
layers move the slowest, while the top and middle layers
move the fastest.
Continental Glaciers
Continental glaciers are large ice sheets on flat lowland
areas. The ice can be about one kilometer thick, and
moves very slowly, sometimes as a result of moving
alpine glaciers. They leave behind hilly deposits of debris
or scoured bedrock. These giant ice sheets weight down
on the continent, and after retreating, the continent
moves back up (also known as isostatic rebounding)
Glacial Erosion
Plucking
Rocks attach to the glacier and get ripped away. This process speeds up when
melt-water seeps into cracks, freezes, and cracks the rock.
Abrasion
Plucked rocks that are attached to the glacier scrape at rock surfaces as the glacier
moves.
Rock flour: Fine powdery rock material left behind as a result.
Depositional Material
Drift
Any deposits left behind by a glacier, often as a result of ice melt, are known as
drift.
Till
The unsorted and unstratified material left when glacial ice melts is known as till.
This includes rock flour, sand, gravel, and boulders.
Outwash
The well-sorted and stratified material left from running glacial melt-water is
known as outwash. The heaviest material deposits first, followed by lighter.
ALPINE GLACIER
FEATURES
Features
1
2
3
4
5
6
7
8
9
Horn
Cirque
Arête
Medial Moraine
Lateral Moraine
Crevasses
Col
Snout
U-Shaped Valley
Features
1
2
3
4
5
6
Tarn
Cirque
Striations
Truncated Spur
Hanging Valley
Bridal Veil Falls
Glaciated Definitions
Horn: A pyramidal peak that occurs when cirque glaciers erode a mountain
on multiple sides
Cirque: Hillside hollow made from the erosional activity of glaciers
Arête: Two cirques that erode the mountain between them, forming a sharp
ridge
Crevasse: Deep cracks on the glacier’s surface, formed when the glacier moves
over uneven rocks
Col: A mountain pass that is formed when two cirques erode the arête
between them
Snout: Glacier’s leading edge
U-Shaped Valley: Shape of a glacial valley; flat bottom and steep sides
Post-Glaciated Definitions
Medial Moraine: A strand of debris going through the middle of a valley
because of joining tributary glaciers
Lateral Moraine: Rock material attached along the glacier’s side that has been
ripped from the valley walls
Truncated Spurs: The area where the V-shaped valley cuts off into a U-shaped
valley
Tarn: Lake that comes about when a cirque gets filled with water
Hanging Valleys: Tributary glacial valleys that joined with the main valley
glacier, melted away, and were left hanging high at the side of U-shaped
valleys
Striations: Grooves made in bedrock by abrasion
CONTINENTAL
GLACIER FEATURES
Features
1 Ground Moraine
2 Recessional Moraine
3 Terminal Moraine
4 Esker
5 Drumlin
6 Outwash Plain
7 Kettle
8 Finger Lake
9 Pro-Glacial Lake
10 Erratic
11 Braided Stream
Glaciated Definitions
Ground Moraine: Debris deposits that were carried by the glacier in its lower
ice layers
Terminal Moraine: Debris left at the farthest advance of the glacier
Recessional Moraine: Debris deposited at the snout when ablation and
accumulation are happening at the same time
Outwash Plains: Area where ice melts and the melt-water deposits stratified
debris
Crag & Tail: Created when a glacier hits a very hard rock (igneous) and gets
stuck on one side of the rock (tail) while the rest of it moves on
Post-Glaciated Definitions
Pro-Glacial Lake: Lake formed when the terminal moraine acts as a natural
dam and is filled with melt-water
Esker: Stratified deposits left behind from melt-water
Ribbon Lakes: After glaciation, long, narrow gouges fill up with glacial meltwater
Kettle Lakes: A chunk of the glacier gets left behind, eventually melts, and
fills in its hole to make a lake
Drumlins: Deposits left behind that are hill-like
Erratic: A large boulder that is deposited far from where it originated from
Benefits of Glaciers
Freshwater
Melt-water is freshwater and is left in large quantities. It is
drinkable and also provides animals with habitats.
Hydroelectricity
Damming tarns allows for a renewable source of energy.
Tourism
Glaciers attract people for sight-seeing and recreation,
which earns the economy some revenue.
Construction
Large deposits of sand and gravel are left behind by glaciers
which can be used to build roads.
Farming
Glaciers leave behind minerals and rich soil for farming and
grazing (Prairies).
Disadvantages of Glaciers
Flooding
When glaciers melt, they can cause floods. Excessive melting can
lead to the ocean level rising and coastal cities getting submerged.
Temperature
Glaciers make global temperatures more extreme. Also, the sun
reflects off of the ice, which heats the planet
Freshwater in Oceans
Some animals are unable to survive in freshwater when it melts off
a glacier and enters the ocean
Crevasses
Humans and animals can fall into and become trapped in crevasses
Loss of Freshwater
Clean drinking water goes to waste when glaciers melt into the
ocean.
Projects
Teachers have reason to give their poor students more projects to
work on (although this was a good project!)