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In this lesson we are going to discuss about glaciation and the way ice moves

Answer Text:
Glaciation
- Action of moving ice.
Glacier - Mass of ice moving outward from an area of accumulation.
- Formed when snow accumulates on the surface, lower layers are compressed to a harder mass resulting in
opaque ice due to air bubbles and accumulation continues compressing lower layers squeezing out air forming
glassy ice called glacier.
Types
a) Cirque glacier - ice occupying a cirque
b) Valley glacier - Ice confined within a valley
c) Piedmont glacier- Glacier formed when valley glaciers converge at the foot of the mountain.
Ice bergs - Large mass of ice floating in the ocean formed when an ice sheet moves to the sea e.g. in Arctic and N. Atlantic Ocean.
Ice sheet - Continuous mass of ice covering a large area on the earth’s surface.
Ice caps - Ice covering the mountain peak.
Snow line - Line beyond which there is a permanent snow cover.
Ways of Ice Movement
a) Plastic Flowage
- Movement of ice like a viscous liquid.
- Great pressure is exerted at the bottom sides and centre causing some ice particles to melt slightly and move slowly
down hill like a viscous liquid.
b) Basal Slip
- Movement of ice by sliding over the underlying rock.
- Pressure is exerted on deepest layers of ice in contact with the rock beneath causing melting.
- A film of water is created which acts as a lubricant between the ice and the rock causing ice to slip and slide over the rock and move down
slope.
c) Extrusion Flow
- Movement of ice by spreading out.
- Ice accumulates building to great thickness at the centre causing compression of layers of ice beneath.
- The layers beneath are forced to spread out where there is less pressure.
d) Internal Shearing
- Breaking of ice into smaller pieces which move alongside one another.
- Uneven movement causes ice to develop cracks on the surface.
- The glacier breaks into smaller pieces which move alongside each other down slope.