Earth science for schools by Moorland School

When does a solid flow? ?

Earthquake vibrations tell us that the mantle is as strong as steel. But the shape of the Earth suggests that it is a spinning fluid droplet. Other clues exist which tell us that the rocks beneath our feet can flow and move.

The mantle rock is effectively solid if you think of conventional time periods (days, years and even decades). Geological time is measured in many millions of years, the Earth is 4.6 million years old. The mantle does flow like a liquid, but it happens incredibly slowly.

Scandinavia

This part of Northern Europe appears to be slowly rising (about 3cm per year) and it is not situated in a geologically active region such as the edge of a tectonic plate . One explanation for this is that the region was once covered with a huge ice sheet several kilometres thick during the last ice age. The enormous weight of this sheet pushed Scandinavia about 300 metres lower (this process took thousands of years to happen). When the ice sheet melted the weight was removed and the region started to rebound back into shape.

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Moorland School
Clitheroe,
Lancashire
BB7 2AJ
England
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