Why do glaciers affect the land?

Answer 1

by moving along the ground

answ2

1. At their head catchment area, the glacier will collect the annual snow fall, and commence to move it downwards. This process opens up cracks (bergschrunds) between the snow and the rock, for the rock will be warmer than the snow. (heat from the interior) Into these crevices, sometimes many feet wide, rocks will fall from the mountain above, and water will flow off the day-warmed rocks.

2. In the main long body of the glacier there will be occasional steps in the valley bedrock, and there will be steps where a minor glacier branch joins a larger glacier. At these step points, a crevassed ice-fall will form, and again any moraine debris from the surface will become entrained in the ice.

These entrained rocks and debris will be ground along the bedrock by the motion of the glacier, and produce a very fine rock flour in the process.

Thus at the base of the glacier, we have water from melt, boulders and debris, and rock flour. These will be all ground along by the glacier above. Small and medium boulders will be ground to a rounded form, larger boulders will have their sharper corners ground off, but at any time, much of their body will be embedded in the glacial ice, and they will rotate only slowly. As these are dragged across the bedrock, they will produce the striae - the glacial scratches and gouges in the bedrock.

3. Upvalley from the snout of the glacier, is the ablation (wastage) zone, where some of the ice mass will sublimate directly to water vapour, and much will melt. Near the snout, the glacier may be completely covered by rock moraine, and kettle holes will form due to uneven melting. Immediately downvalley of the glacier, a melt lake may form, and this feature is very destructive of the remaining ice. When masses of ice fall into the melt lake, minor tsunami (but ten metres or so high) may be created and these are dangerous to humans.

A glacier can move rock from the mountains to the plains hundreds of times faster than simple riverine processes will do.

Unlike a river, glacial ice can extend far below the surface level, and (where I live) glacial lakes 300m above sea level have their depth up to 100m below sea level.

A fiord glacier may have its bed several hundreds of metres below sea level, the ice breaking off where the fiord enters the sea, and the ice becomes buoyant; and depositing a mound of moraine at the mouth of the fiord.

Answer 2

Glaciers move large amounts of rock and earth. The meltwater also erodes the land and creates lakes.