Rivers and coasts, Year 10: glaciers and their landforms (Glacial landscapes option)

Southern England

提示Think of the part of the island furthest from the Scottish mountains where the ice built up.

为什么Ice sheets spread from the mountains of Scotland, the Lake District and Wales and covered most of northern Britain. The ice never reached the far south of England. That land was frozen tundra, not ice-covered, which is why it has no corries or glacial troughs.

Rotational slip (of glacier ice)

提示The ice pivots like a person sliding forward out of a deep armchair.

为什么Gravity pulls the ice downhill, and meltwater at its base helps it slide. In a hollow the ice moves along a curved path, pressing hardest on the floor. This is why a corrie is deepest in the middle and has a raised lip at its front.

bulldozing

提示Name the yellow machine with a wide blade that clears a building site.

为什么A glacier carries rock on top of it, inside it and frozen to its base. It also pushes material in front of its snout as it moves forward. When the ice melts back, the pushed-up material is left as a ridge.

Till (boulder clay)

提示Four letters; it is also what a shop keeps its money in.

为什么Ice cannot sort what it carries. When it melts, everything from fine powder to large rocks is dumped together, and many of the stones are still sharp-edged. Deposits laid down by rivers are different: they are sorted by size and the stones are rounded.

Meltwater streams flowing from the glacier

提示Ask what ice turns into at its warm lower end.

为什么Running water drops its heaviest load first and carries finer material further, so its deposits are sorted. Streams leaving the snout of a glacier spread sand and gravel over the ground in front of it. Ice itself cannot sort what it carries.

It loosens rock on the slopes above, which falls onto the ice

提示Look up at the cliffs on either side of the valley.

为什么Water in cracks freezes at night, expands by about 9 per cent and widens the crack. Pieces break off the valley sides and the back wall of a corrie and land on the glacier, which carries them away. The rock also gives the ice tools for abrasion.

tarn

提示Four letters, rhyming with "barn".

为什么A corrie is deepest in the middle and has a raised rock lip at the front, where the ice eroded less. After the ice has gone, rainwater and streams collect behind the lip. Not every corrie holds a lake.

An arête

提示A French word; it is also French for a fish bone.

为什么Each corrie's back wall is cut back by plucking and freeze-thaw weathering. When two corries lie on opposite sides of a mountain, the rock between them is narrowed until only a thin ridge is left. Freeze-thaw keeps the crest sharp.

3

提示Count the faces a pyramid needs, not including its base.

为什么When corries erode back into a mountain from several sides, their back walls meet. The summit is left as a sharp, pointed peak with steep faces, and arêtes run down from it between the corries.

Truncated spurs

提示The first word means "cut short".

为什么A river winds around ridges of hard rock, but a glacier is too rigid and powerful to do that. It moves straight down the valley and erodes through anything in its path. The cut ends are left as steep, cliff-like sections of the valley side.

The small tributary glacier eroded far less deeply than the large main glacier

提示Compare the weight and power of a thin stream of ice with a thick one.

为什么A thicker glacier is heavier and erodes its bed more. The main glacier cut its trough far deeper than the side glaciers cut theirs. When the ice melted, the side valley was left opening part-way up the main valley wall, often with a waterfall.

A ribbon lake

提示It is named after the strip of fabric you tie round a present.

为什么The glacier eroded more deeply where the rock of the valley floor was softer or where the ice was thicker. That left a long hollow in the trough. After the ice melted, the hollow filled with water.

moraine

提示Seven letters, beginning like "moral" and ending like "rain" with an extra letter.

为什么The debris comes from freeze-thaw on the slopes above and from the glacier's own plucking and abrasion. It is named by where it lies: along the sides, down the middle, under the ice or across the valley at the snout.

Lateral; medial; terminal

提示In order: think of "sideways", of "median" and of the last stop on a railway.

为什么Rock falling from the valley walls collects along each edge of the ice. Where two glaciers meet, their two inner edge lines join into one line down the centre. Debris carried to the snout is dropped where the ice melts, building a ridge across the valley.

The furthest point that the glacier reached

提示It is the high-water mark of the ice.

为什么At its snout a glacier melts as fast as it moves forward, so debris keeps arriving and piling up in the same place. When the climate warms and the ice melts back, the ridge is left behind as a marker of its greatest advance.

An erratic

提示The word also describes behaviour that wanders and is hard to predict.

为什么A glacier can carry a rock many kilometres from the outcrop it was plucked from. When the ice melts, the rock is left wherever it happens to be. Matching it to its source shows the route the ice took.

The gently tapering end

提示Think of the tail of a raindrop sliding down a window.

为什么Drumlins were shaped beneath moving ice. The steep end faced the oncoming ice and the long tail was drawn out in the direction of flow. They often occur in groups called swarms, which look like a basket of eggs.