Suffolk's chalky clay soils are formed from 'till' or 'boulder clay'' - this is material that was scraped up by the great Anglian Glaciation about 470,000 - 430,000 years ago and then left behind when the ice sheet melted. In places this layer is nearly 70 metres thick.
Nearly all of Suffolk was covered by the Anglian Glaciation but no subsequent ice sheets reached this far south - the last glaciation, which ended about 10,000 years ago, only reached the north Norfolk coast.
On either side of the clay till are areas with sandy soils. These are the result of 'outwash' from the melting glaciers and of windblows from the main glacial deposits
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