Glaciers

Glaciers are slow-moving masses of  ice that exist where more snow falls than melts. They occupy about 10% of the Earth's land, mostly in Greenland and Antarctica. As they move, glaciers can widen and deepen valleys, flatten forests and grind boulders into pebbles.

Types of glaciers
 Alpine glaciers form on the crests and slopes of mountains and are also known as "mountain glaciers", "niche glaciers", or "cirque glaciers". An alpine glacier that fills a valley is sometimes called a valley glacier.

 The largest glacial bodies, ice sheets or continental glaciers, cover more than 50,000 km² (20,000 mile²).

 Ice shelves are areas of floating ice, commonly located at the margin of an ice sheet.

Ice streams are fast-moving sections of an ice sheet.

How do glaciers move?

Glaciers move, or flow, downhill due to the ice building up in the middle, forcing the edges to expand and gravity.
Another type of movement is through basal sliding . In this process, the glacier slides over the terrain on which it  sits, lubricated by the presence of liquid water.

 The speed of glacier movement is partly determined by friction. Friction makes the ice at the bottom of the glacier move more slowly than the upper portion. In alpine glaciers, friction is also generated at the valley's side walls, which slows the edges relative to the center.

Glacier words to know:

Deposition occurs when the moving ice stops and melts, depositing rocks, sand and dirt that it carried along.

As the glacier flows over the bedrock's fractured surface, it softens and lifts blocks of rock that are brought into the ice. This process is known as plucking.