2A.2 Present and past Pleistocene distributions of Ice cover Flashcards
Definition and importance of Cryosphere -
Ice cover is collectively known as the cryosphere and be classes into a number of different ice forms. Covers 13% of the planets surface.
Ice regions can be found in high latitudes for example -
Arctic and Antarctic Circles of more than 65 degrees north and south of the equator of polar cells. Due to very little and insufficient sunlight throughout the year.
Ice regions can also be found in high altitude for example at -
Mountain ranges which can be any latitude (for example the Alps) Ice is often constrained within the topography
Thermal characteristics of Polar glaciers -
Cold based glaciers have a very cold surface temperature of -20 to -30 degrees and their base is frozen to the bedrock beneath. Little glacial movement only one that can happen is internal deformation.
Thermal characteristics of temperate glaciers -
Warm based glaciers are not frozen to the bedrock surface they rest on, at their there is a layer of water, allowing the base of the glacier to slide and move, through basal sliding.
Classification of ice masses -
Constrained - no dome shape, so the movement is influenced by the surroundings - Cirque glaciers
Unconstrained - The flow and shape is not influenced by its surroundings, ice sheets, shelves and caps.
Ice sheets -
Ice sheets are unconstrained types of glaciers, they are largely domed shaped and cover underlying topography found more commonly in Antarctica and Greenland. Cover more than 50,000 km cubed
Ice caps -
Unconstrained glacier types which covers less than 50,000 km cubed and can flow in multiple directions, these are versions of smaller ice sheets E.G Svalbard
Ice fields -
Ice fields are ice sheets covering a mountain plateau with some mountain peaks flowing through
Ice fields -
Ice that covers a mountain plateau, doesn’t extend to high-altitude areas for example the Himalayas, unconstrained
Valley glaciers -
Unconstrained, ice is surrounded by high mountains and fills the valleys, ribbon shaped and vary in length from a few kilometres to over 100 km , examples can include in the Himalayas
Cirque glaciers -
Unconstrained, smaller glacier occupying a hollow on the mountain range, carves out a corrie or cirque, smaller versions are known as a niche glacier.
Cold based glaciers -
Referred to as polar glaciers, which occur in high latitude particular in Greenland and Antarctica ice temperature is usually below 0 degrees, extreme surface temperature can be as low as -20 degrees - - degrees. Relatively little surface melt in the short and cool polar summer, glacier is permanently frozen to it’s bed.
Warm based glaciers -
Referred to as temperate glaciers which occur in high altitude regions outside a polar region, the temperatures fluctuate below and above pressure melting point. Due to increased pressure of overlying ice, water exists as a liquid at temperatures below 0 degrees, glacier has lot’s of debris in it’s basal layers and significant in subglacial depositional features.