Glaciation Flashcards
When was the start of the last ice age?
18,000 years ago
When did the last glacier end?
10,00 years ago
Warm periods are called what?
Interglacial periods
What are cold periods called?
Glacial periods
What is a glacier?
A mass of moving ice or a river of ice
It may move in a valley like a river or from a mountainous area, like a tongue of ice.
How much of the earth do glaciers cover now?
1/10th of the world
Where can they be found?
On two locations
- High latitude- further away from the equator and close to the poles
- High altitude- further away from the poles and found in mountainous areas. As long as the mountain is high enough, there will be glaciers near the equator
Example of a glacier
Mer de glacé glacier
How does a glacier form?
- Snow collects in a hollow hole in a mountainside
- Snow accumulates and more snowfall increases the weight
- The weight compresses the bottom of the layers into solid ice
- If the snow does not melt and snow continues to fall, the ice mass will become heavier and bigger.
gravity will soon cause the snow and ice to move downhill very slowly.
What is frost shattering?
At how of weathering When water repeatedly refreezes and puts pressure on the rocks around it breaking them down.
What is abrasion?
A process of erosion where the moraine carried by the glacier erodes the valley sides and floor. Abrasion causes striations, which indicate what direction the ice was moving in.
What is plucking?
Plucking is a process of erosion where glacial ice freezes onto the rocks and when it moves away, it pulls large pieces of rock with it.
Name the landforms created by glacial deposition
Arêtes Pyramidal peak Corrie U shaped valley (glacial troughs) Truncated spurs Hanging valleys
What is a corrie?
A corrie is a large bowl shaped hollow in a mountainous area and snow builds up so they are generally the source of ice for glaciers.
The hollow is deepened and widened by abrasion and plucking.
The overdeepening leads to an armchair shaped characteristic of a corrie and causes a rock lip to be formed.
How is a corrie formed?
- Snow accumulate is east and North facing hollows
- Snow gets compressed into ice and moves down hill
- Frost shattering and plucking create a steep back wall
- Abrasion deepens the hollow and forms a rock basin
- A rock lip is left where the rate of erosion has decreases
- The height of the rock lip is increased by the deposition of moraine
- The rock lip and moraine act as a dam
- A corrie lake (tarn) fills the rock basin fate the ice age.
What is an arête?
An arête is a narrow knifed ridge on at the mountain top generally form around a corrie.
What is a pyramidal peak?
When 3 or more Corrine’s cut back into the same mountain and leave a ‘pyramidal peak’
What is a glacial trough?
A landform that has eroded the whole valley and has widened,deepened and straightened its valley.
What are the characteristics of a glacial trough? Explain what they are.
Truncated spur- interlocking spurs that had been truncated as the glacier cuts straight through the landscape.
Hanging valley- between truncated spurs are hanging valleys which have not been deeply eroded as the main valley.
Name the landforms created by glacial deposition
Drumlins
Erratics
Crag and tail
Moraines
What is an erratic?
A type of land form, a boulder that has been transported and deposited by a glacier which is different to the bedrock upon which it is sitting.
Erratics are useful because the indicate the patterns of former ice flow.
What is moraine?
Moraine is a type of landform that is created when a glacier deposit as material (till) that it has been transporting, it is made up of u sorted angular rocks.
There are several types of moraine: recessional,lateral,ground,medial and terminal.
What is recessional moraine?
It marks the interruptions of the retreat of the glacier.
What is terminal moraine?
It is found at the snout and marks the maximum advance of the glacier
What is lateral moraine?
It is produced by Frost shattering of the valley sides and is carried at the sides of the glacier
What is medial Moraine?
It is found in the centre of the glacier
What is ground moraine?
It is found beneath a glacier and forms part of the valley floor
How are drumlins formed?
Drumlins are formed by till. The are elongated features that can reach a kilometre or more in length, 500m width and over 50 m in height
What is a group of drumlins called?
A swarm
How much of the earths surface was covered in the last ice age?
30%
