HAT IS ICE?
Ice is the solid state of water (H20 molecule). In a glacier, ice is mixed with air bubbles, making it 0.9 times denser than water. For that simple reason, ice floats on water.
GLACIER ICE FORMATION
During winter, snow piles up and compresses. Its hexagonal crystals start to deform due to compaction, releasing air, giving crystals a more granular shape. This brings us to the second stage of snow: névé. As new layers of snow accumulate, the weight of said layers compresses the snow into glacial ice.
HOW LONG DOES IT TAKE TO FORM A GLACIER?
It varies considerably from one glacier to the next. It can take just a dozen years for temperate glaciers like the Patagonian glaciers, or up to hundreds of years for cold glaciers like the ones in Antarctica. Contrary to popular belief, the warmer the glacier is, the quicker the ice forms, because the snow crystal needs moderate temperatures (above 0ºC, 32ºF) in order to fuse into glacial ice. In Antarctica, temperatures are so low that the snow compaction process takes much longer.
There are two phenomena that cause movement: sliding and internal deformation.
- Sliding is produced by friction between the base of the glacier and the rocky substrate, which creates a thin film of water that allows movement. It can also be caused by water leaking from the upper layers down to the base of the glacier.
- Internal deformation is produced by the pressure (approximately 650 tons per cubic meter) exerted by the weight of the ice. This tension leads to deformation, which causes the glacier to move.
ANATOMY OF A GLACIER
The accumulation zone is the top of the glacier, where snow accumulates.
The ablation zone is the bottom of the glacier, where there is a loss in glacial mass.
The equilibrium line separates the accumulation zone from the ablation zone.
A moraine is an accumulation of rock, sand or clay that is picked up and transported by glaciers as they advance.
There are several kinds of moraines:
Lateral Moraine: as its name states, it consists of sediment deposited on the sides of a glacier. Medial Moraine: is the junction of two glaciers merging their lateral moraine deposits.
Terminal Moraine: this moraine marks the furthest advance of a glacier and the point where it starts to recede.
Internal Moraine: is an accumulation of sediment which falls into crevasses and is trapped in the ice, giving the ice a “dirty” appearance.