Glaciers Flashcards
What is a glacier? How do they form?
A glacier is a large mass of ice that moves slowly over land under its own weight. Glaciers form through the accumulation and compaction of snow over many years. As successive layers of snow accumulate, the weight of the overlying snow compresses the lower layers into dense ice. Over time, the ice becomes thick enough to flow downhill under the force of gravity, forming a glacier.
What are the differences between continental and alpine glaciers?
Continental Glaciers: Also known as ice sheets, continental glaciers are vast ice masses that cover extensive areas of land. They are found in polar regions such as Antarctica and Greenland. Continental glaciers are characterized by their immense size and relatively flat topography.
Alpine Glaciers: Alpine glaciers, also known as mountain glaciers, occur in mountainous regions and are confined to valleys or cirques. They are smaller in size compared to continental glaciers and are often found in high-altitude areas. Alpine glaciers flow down valleys, sculpting the landscape as they move.
What part of a glacier flows fastest? Slowest? Why?
The fastest-flowing part of a glacier is typically the center or axis of the glacier, where ice experiences the least resistance to flow. This region is often referred to as the “zone of maximum flow” or “zone of velocity.” The slowest-flowing parts of a glacier are the edges or margins, where ice encounters frictional resistance from the valley walls or surrounding terrain. Additionally, the base of a glacier may also flow faster than the surface due to the presence of meltwater acting as a lubricant, reducing friction.
Define and describe the following: striations, till, outwash, drift, moraine.
Striations: Striations are parallel scratches or grooves on bedrock surfaces caused by the movement of glaciers. They are formed as glaciers transport rock fragments and debris, which scrape and scratch the underlying bedrock as the glacier moves.
Till: Till is unsorted and unstratified sediment deposited directly by glaciers. It consists of a mixture of clay, silt, sand, gravel, and boulders, deposited as the glacier retreats or melts.
Outwash: Outwash is sediment deposited by meltwater streams flowing from glaciers. It is usually well-sorted and stratified, consisting of sand, gravel, and finer sediment transported and sorted by meltwater.
Drift: Drift refers to all sedimentary deposits, including till and outwash, left behind by glaciers.
Moraine: Moraines are accumulations of till deposited by glaciers. They can be classified as lateral moraines (deposited along the sides of glaciers), medial moraines (formed where two glaciers merge), terminal moraines (deposited at the furthest extent of a glacier), or recessional moraines (deposited as a glacier temporarily stalls during retreat).
How does a ‘wineglass valley’ form?
A wineglass valley, also known as a U-shaped valley, forms through the erosional action of glaciers. Initially, a V-shaped river valley is carved by the flow of water. When a glacier occupies this valley, it erodes the valley floor and walls through abrasion and plucking, widening and deepening the valley into a U-shaped profile resembling an inverted wineglass. After the glacier retreats, the valley may be further modified by other erosional processes such as rivers or weathering.
