23.4 Glaciers and Wind

What is a continental glacier?

A continental glacier is a thick sheet of ice that covers a huge area, such as a continent or large island.

How does a dune move?

A dune moves as the wind picks up sand from the back of the dune and blows it to the front.

What is a valley glacier?

A valley glacier is a glacier that occurs in a high mountain valley. It usually begins near a mountain peak and winds down through a valley formed originally by a stream.

What is abrasion?

Abrasion is a type of mechanical weathering. Abrasion by wind occurs in much the same ways as abrasion by flowing water. Wind blows sand against other rocks, slowly sandblasting them away an removing the weathered particles.

How does the speed of wind effect erosion?

As with running water, the speed of the wind determines the size of the materials it carries. Slower winds carry only small particles, like dust. Faster winds have more energy and can lift larger particles, such as sand grains. A constant, strong wind can produce a large cloud of dust or sand.

Glaciers move much more slowly than rivers, yet they are very effective at eroding and depositing sediment. Why?

Because glaciers tear away the underlying rock as they move.

What are cirques, how are they formed, and what do they look like?

Cirques are large bowl-shaped valleys (usually high) on a mountainside caused by the glacial erosion of valley glaciers. They look as if they were made by a giant ice cream scoop.

What features are formed by glacial erosion?

Cirques, horns, U-shaped valleys, and glacial lakes.

What are the two types of glaciers?

Continental and Valley

What is deflation?

Deflation occurs when wind picks up and carries away loose surface material. In dry regions where winds are strong, sand and dust are lifted from the surface and carried away. Over time, the surface of the ground is lowered. Larger rocks are left behind, forming a rocky surface that covers much of the land in dry regions.

What are dunes?

Dunes are deposits formed from windblown sand. Over time, sand dunes can move great distances.

What features are deposited by wind (or: What features are wind depositions?)?

Features deposited by wind include sand dunes and loess deposits.

Where and how do glaciers form?

Glaciers form in places where more snow falls than melts or sublimates. As the layers of snow pile up, the weight on the underlying snow increases. Eventually, this weight packs the snow so tightly that glacial ice is formed.

What happens if several cirques form close together?

If several cirques form close together, a ridge may be left between them. If several ridges connect to form a pyramid-shaped peak, the peak is called a horn. Picture (I believe the "aretes" are the ridges): http://classconnection.s3.amazonaws.com/637/flashcards/268637/png/screen-capture-11337663412142.png

Where does most wind erosion occur?

In dry areas of the world (like deserts).

Describe plucking.

In plucking, glacial ice widens cracks in bedrock beneath the glacier. Pieces of loosened rock are then frozen to the bottom of the glacier, which carries them away. The pieces of rock that are stuck to the bottom and sides of the glacier act like sandpaper. As the glacier moves, it scrapes the bedrock and soil under it and along its sides.

What are loess deposits, and what does loess consist of?

Loess deposits are formed from windblown dust. Loess consists mainly of finely ground particles. The two major sources of loess are deserts and glacial deposits.

What are moraines?

Moraines are mounds of sediment at the downhill end of the glacier and along its sides.

Describe the movement of glaciers.

They appear stationary, but they are constantly moving. The force of gravity pulls the ice downhill. The ice flows slowly, like honey dripping down a spoon. Sometimes the pressure is great enough to melt the ice at the base of the glacier. This melting can aid the motion of the glacier, with the ice sliding along the bottom. Like a river, a glacier flows fastest in the middle and slowest along the sides.

What do glaciers do to the valleys through which they flow, and how do U-shaped valleys form?

They widen and deepen them. When glaciers flow through V-shaped valleys cut by running water, they widen them into U-shaped valleys. Glacial valleys are U-shaped because the moving ice scours the entire valley, eroding rock from the valley's bottom and sides. Ex. of U-shaped valleys carved by glaciers: Glacier National Park in Montana

How do glaciers erode rock?

Through abrasion and plucking.

What is till?

Till is glacial sediment. It is an unsorted mixture of sediment containing fragments of many sizes. Giant boulders, gravel, sand, and pulverized rock dust are all found in till. Glaciers deposit till as they melt. This till forms moraines.

How do continental glaciers differ from valley glaciers (how do they erode)?

Unlike valley glaciers, continental glaciers tend to level large surface areas through the scraping and grinding of thick ice. Continental glaciers can enlarge and deepen natural depressions in the surface. These depressions then fill with water when the glaciers retreat. Examples of glacial lakes formed by that process: Great Lakes and Finger Lakes in New York

A glacier gather and transports a huge amount of rock and soil as it moves. What happens when a glacier melts?

When a glacier melts, it deposits its load of sediment, creating a variety of landforms.

How does wind cause erosion?

Wind erodes the land by deflation and abrasion.

Can sand dunes take different forms?

Yes--it depends on wind direction and how much sand is available.

Most of Earth's fresh water is frozen in the ________________ glaciers that cover Antarctica and Greenland.

continental