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Description
Flashcards by Yu-Qing Tham , updated more than 1 year ago
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Created by Yu-Qing Tham
over 8 years ago
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| Question | Answer |
| The big picture | Glaciers are like rivers of ice. They flow! Today they cover about 10% of the Earth's land Much of Britain was covered by glaciers during the last ice age, which ended about 10000 years ago. Glaciers scrape and shape the land as they flow over, giving special landforms. We can still see these landforms in Britain today. |
| During the ice age, water levels in the ocean were much lower than today. (up to 120m lower) That's because so much water was locked up in ice. The water drained away from shallow parts of the ocean floor. They became land. | 20000 years ago, there was nobody in the British Isles. We had turned up earlier in the ice age - 40000 years ago. We had walked here from other parts of Europe. But as the ice sheet was shrinking, it got too cold for us so we left. Then about 12000 years ago, when the ice sheet was shrinking we came back to the British Isles. |
| But there were animals there 20000 years ago. There were woolly mammoths and bison and Artic foxes, which would survive the tundra winter. And in summer, when plants grew in the tundra, large herds of reindeer and antelope arrived from other parts of Europe, to feed. | As Earth warmed up again, the ice melted. The water levels rose again, and cut us from the rest of Europe about 8100 years ago. But the ice had changed the landscape - & we can still see the results today. |
| What are glaciers? | During the last ice age, it covers about a third of Earth's land. Today it covers about a tenth. The ice doesn't just sit there. It flows! Glaciers are large masses of ice, that flow across the land, and down slopes. Giant glaciers, that covers huge areas, are called ice sheets. |
| Where are the glaciers? | There are glaciers on all 7 continents. Far from Equator, at the top and bottom of the world, ice sheets cover Antarctica & most of Greenland. Between them they have over 99% of Earth's ice. They are more than 4km thick in places. Earth's other glaciers are much smaller. Most are high up in mountains, where it is also very cold. Most of Earth's big mountain ranges have glaciers. They are called mountain glaciers. |
| Glaciers depend on snow. In those cold places, snow falls layer upon layer. Over time the layers below get compacted to ice, like when you squeeze a snowball very hard. It could take a layer of snow 10m thick to make a layer of ice 1m thick. As the ice gets heavier it starts to flow under the pressure of its own weight. | Glaciers flow. First, ice flows inside a glacier, because the ice crystals slide over each other under pressure. Second, the ice at the bottom of the glacier may melt;then the whole glacier slides along on the water. Ice sheets just flow a few ms a year. Mountain glaciers flow fast down their slopes - 300ms a year or more. |
| Where do they flow to? | A mountain glacier flows down the side of the mountain in a valley. Eventually it reaches a place where it melts. In ice sheets, the ice flows out the thinnest parts. In Antarctica it flows into the ocean in places and floats as an ice shelf. Bits of ice break off and form icebergs. |
| Corrie A corrie begins as a sheltered hollow, where snow buils up year after year. | |
| Arête when 2 corries form side by side, the glaciers erode the rock between them, leaving a sharp ridge of rock. | |
| Pyramidal peak when 3 or 4 corries forms around a mountain top. The glaciers erode their back walls, cutting into the mountain top. | |
| U-shaped valley | |
| Hanging valley | |
| Moraines | |
| Erratics | |
| Drumlins | |
| U-shaped valley on an OS map | |
| Corrie on an OS map |
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