Glaciation Flashcards
What is an ice age?
An ice age is a period of time when a part(s) of Earth is covered in ice.
How long ago did the last ice age end?
The last ice age hasn’t ended yet. However, the last glaciation ended 15 000 - 18 000 years ago. We are currently in an inter-glacial.
How much of the world did the ice cover and where?
Ice covered about 30% of the world in Northern countries, high altitudes and Antartica.
What happened to places not covered by ice?
cooler / different ecosystems / different. (Everywhere changed).
Why do ice ages start and finish?
Ice ages start and finish because of natural climate changes on Earth.
On average, how much cooler was the world in the last ice age?
The was about 7°C colder in the last ice age.
What animals lived in the last ice age but are now extinct?
Some animals which lived in the last ice age but are now extinct are:
- the wooly rhino
- the mammoth
- the saber-toothed tiger
- ground sloths
- the stag moose
- etc.
Did dinosaurs exist during the last ice age?
No, dinosaurs did not exist during the last ice age.
How much lower were sea levels during the last ice age?
Sea levels were about 100-200m lower during the last ice age.
What is a glacier?
A glacier is a large sheet of ice made up of snow that has been compressed over many years to form solid ice.
How does a glacier start?
Glaciers start when snow falls and a part of it doesn’t melt during the summer (a small bit remains). Over the years, this procedure will build up to form a glacier (made of snow which has also compressed during a long period of time (hundreds of years) to create ice).
Why do glaciers start near the top of mountains on north facing slopes?
Glaciers start near the top of mountains on north facing slopes because this is where it is coldest and therefore the snow will not melt during the summer.
How do glaciers move?
Glaciers move slowly down the mountain with help from gravity. The overlying ice causes the ice to deform around the rock and ‘flow’. The under-glacier rivers also help it move.
What is glaciation?
The effects of large bodies of ice on the landscape and the distinctive landforms created by erosion, transportation and deposition.
What is plucking?
A procedure that happens when the glacier ‘flows’ slowly down the mountain. As it moves it will pick stones up on the way which will stick to the ice.
What is abrasion?
The process will take place when the ‘plucked’ stones scrape at the landscape on the sides of the glacier when it is slowly ‘flowing’ down the mountain. Friction between the rocks will smoothen out the landscape rock.
What is nivation?
Snow compresses into ice and molecules…
How is a corrie / cirque / cwm formed?
Snow builds up in a shallow hollow behind a small lip and nivation takes place as it is compressed during the years. As its own weight and gravity will encourage it to move downhill in rotational slip, the glacier will pull away from the steep backwall to form a bergschrund. It will also pluck stones from the rock and pull them along to cause abrasion which will smoothen the landscape. All of this will steepen the corrie sides and deepen the corrie floor. Later on, the ice will melt in the corrie and becomes a small lake.
In icy places, how can flowing water also help to shape the landscape?
Flowing water will help to form the landscape because it helps the glacier to flow down the mountain which is what carves out the landscape.
How are pyramidal peaks formed?
Formed when three or more corries are weathered and eroded backwards into a mountain top, until a sharp peak is created.
How are aretes formed?
Formed as the backwall and sides of a corrie are weathered and eroded.
What are striations and how are they formed?
Striations are approx. 1mm grooves made by rocks which have been ‘plucked’ at the bottom of the glacier, scraping against the rock. The grooves are all parallel and this indicates the glaciers’s route.
What are truncated spurs and how are they formed?
When the glacier bulldozes through the old inter-locking spurs of the old river valley it cuts them short, or ‘truncates’ them.
How are U-shaped valleys formed?
When the glacier digs deeper into the land, making a straight, deep valley shaped like a ‘U’.
