Introduction to glaciers
- Created by: darcie_cl
- Created on: 25-02-14 11:53
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- Introduction to glaciers
- INTRODUCTION
- Large bodies of ice that flow downhill in response to gravitational forces
- Glaciers range in size from small valleys to vast ice sheets
- Glaciers can be classified according to size and shape and by the glacial ice temperature
- SIZE AND SHAPE
- Niche - patches of snow and glacial ice in small hollows and gullies
- Cirque - glacier that sits in a basin (bowl) feature
- Valley - large streams of ice that glows within a valley from an up-slope cirque or ice cap
- Piedmont - large blobs of spreading ice when valley glaciers expand onto flat land
- Ice cap - done shaped mass of glacial ice that peaks over mountains
- Ice sheets - masses of ice that covers an entire landscape
- Ice shelves - floating ice where glaciers extend out to sea
- TEMPERATURE
- Polar or Cold based
- In very cold environments glaciers are frozen into the bedrock beneath and melting only occurs at the surface during the short summer season
- Temperate or warm based
- In mild summer temperatures melting occurs at the base of the glaciers as temperatures are close to the pressure melting point
- Polythermal
- Glaciers contain both cold and warm ice
- Polar or Cold based
- FORMATION
- Primary source of ice in a glacier is snowfall
- The transformation of snow into ice is a complex sequence of compression, partial melting and refreezing
- Step 1 - the thick snow base (5-10m) is compressed by the weight of the overlying snow into a mass of granular ice crystals = firn
- Step 2 ; summer meltwater from the snow above percolates down into firn and refreezes
- Step 3; the weight of overlying ice squeezes any remaining air bubbles out
- Cross - section through a glacier = bedrock, glacial ice, firn, granular ice (50% air), freshly fallen snow
- FACTORS CONTROLLING OCCURRENCE OF GLACIERS
- Latitude - must be north or south
- Altitude - height
- Aspent - way the glacier is facing
- Contientality - extent/thickness of temperature and precipitation
- Topography - shape of land
- INTRODUCTION
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