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An introduction to geology
An introduction to geology

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4.3 Ice ages build the modern world

The Earth has gone through a number of ice ages. In fact, we are in an ice age at the moment. An ice age just means that there is ice all year round at the North and South Pole, but many of us think of ice ages as times when huge ice sheets, kilometres thick, covered much of northern Europe, Russia and North America. The last ice age like this finished about 12,000 years ago.

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Figure 4.2 Outwash channel from a glacier on Svalbard, carrying a lot of gravel. Person in orange, next to channel, for scale

When these huge ice sheets move across the ground they tear and rip up rocks. At the melting edges of these ice sheets, huge amounts of water come rushing out, carrying some of the rocks with it. When the ice sheets started to melt for the final time and retreated northwards towards the poles, all the rocky material that was stored within them was deposited on the ground. In vast areas of North America and northern Europe, the geology is covered with material deposited by these huge ice sheets. On a geological map this is called ‘drift’.

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Figure 4.3 The top geological map shows bedrock or solid geology only. The lower map is of the same area, but shows where all the superficial material, called drift (that was deposited during ice ages and more recently by rivers), covers the solid geology