Section 8.3 Flashcards
What is a glacier? How much of Earth’s surface do they cover? Where do they form?
A large, moving mass of ice that covers about 10% of Earth’s surface. They form near Earth’s poles and mountainous areas at high elevations.
Where do glaciers form?
Glaciers form in places that have cold temperatures year round. the colds keeps fallen snow from completely melting and each year the snow that has not melted accumulates in an area called a snowfield. The total thickness of the snow layer increases as the years pass, and a glacier begins to form. The weight of the top layer of snow exerts enough downward pressure to force the snow below to recrystalize into ice.
What are valley glaciers?
Glaciers that form in valleys in high, mountainous areas.
How does the movement of valley glaciers occur?
When the growing ice mass becomes too heavy to maintain its shape and begins to flow.
What is the speed of the valley glaciers movement affected by?
The slope of the valley floor, the temperatures and thickness of the ice, and the shape of the valley walls. The sides and bottom move more slowly because of the friction when the glacier comes in contact with the ground.
What are continental glaciers?
Glaciers that cover broad, continent sized areas.
When do continental glaciers form?
Under the same climatic conditions as valley glaciers.
How do continental glaciers move?
In a different way than valley glaciers. A contintntal glacier is thickest at its centre and the weight of the thicker region forces the rest of the glacier to flatten out in all directions.
Why is glacial erosion powerful? Descrive glacial erosion. What is plucking?
Because of the size, weight, and density of glaciers. When a valley glacier moves, it breaks off pieces of Rick in a process called plucking. When glaciers with embedded rocks move over bedrock valley walls, they act like sandpaper by grinding out parallel structures in the bedrock, Small scratches are strait ions and larges scratches are called grooves.
What are moraines?
Glacial till is the mixed debris that glaciers carry. When a glacier melts, the till is left behind. Ridges consisting of till deposited by glaciers are called moraines. Terminal moraines are at the foot of a large glacier and lateral moraines are those at its sides.
What are outwashes?
When a glacier melts, meltwater floods the valley below. The meltwater containers gravel, sand, and fine silt. When this sediment is deposited by meltwater, it is called outwash.
What are drumlins and eskers?
Drum lines are glaciers that move over older moraines that form the material into elongated landforms called drumlins. Long, winding ridges of layered sediments that are deposited by streams flowing under a melting glacier are called eskers.
When do glacial lakes form?
When large blocks of ice break off a glacier. When the large chunk of ice melts it leaves behind a depression called a kettle hole. After the ice block melts, the kettle hole fills with water from precipitation and runoff to form a kettle lake. Cirques can also fill with water and when terminal moraines block off a valley, the valley can fill with water to form a lake.
