DE (W7)

• Glaciers are views as a rock that is unusual due to its solid form being less dense than its liquid form
• ice forms like a sedimentary rock, when snow builds up and the increasing pressure compresses the material, it also has a very low melting temperature
• Glaciers are masses of ice on land that are in motion
• there are two types of glaciers: valley glaciers found on the side of mountains, that act like rivers of ice flowing towards the ocean. And continental glaciers (ice sheets) that are conical in shape and also move towards the ocean
• many glaciers end in ice shelves: ice that lays over the water but is attached to the main glacier,
• Iceberg calving is the process of ice breaking off of the ice shelf into the ocean
• the north pole is not a glacier as it does not rest over land
• the weight of the Greenland ice sheet creates a bowl shaped landmass with mountains surrounding the edge of the island (due to isostasy)
• the Greenland glacier reaches the ocean through ice streams that wind their way through the mountains
• when snow from the winter does not fully melt in summer, more snow accumulates the following year, when this occurs for long periods glaciers form
• glacier formation requires cold temperatures to form: this is why they occur at high latitudes and elevation, they also require moisture (for snow fall to occur)
• the loss of mass of a glacier is called ablation, this happens through: sublimation (solid straight to gas), iceberg calving and meltng
• Accumulation is the increase of a glacier each year due to more snow falling than ice is melted
• the glacial budget is accumulation over ablation
• Antartica is a continental composite glacier consisting of over 100 individual glaciers that each flow from the centre of the glacier to the coast at differing speeds
• the breaking off of ice shelfs can lead to an extreme increase in the rate of flow of the glacier behind it as the shelf holds back the glacier
• glaciers can move through basal slip or plastic flow
• plastic flow occurs within the glacier in clod regions where the base is often frozen to the ground and individual crystals slip against each other and the glacier moves like a river towards the ocean
• basal slip occurs when parts of the glacier move as a single unit like a block of ice sliding down a ramp, this occurs due to a thin layer of melt water at the base of the glacier (due to pressure) providing lubricant
• a surge is the sudden movement of a glacier (6km/yr or more) over several years caused by a build up of pressure at the base
• crevasses occur within the glacier as a result of the glacier's brittle nature near the top (little to no pressure), while plastic flow occurs beneath, they form around valley walls and curves and at irregulars in the floor
• glaciers need cold conditions to form and grow but can remain a constant mass in warmer temperatures until it becomes too hot and the glacier melts completely
• glaciers have a slow reaction to temperature but can melt quickly once it occurs