What is loess

A.� Loess is the name given to wind-blown, glacial silt deposits.

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Q.� What does 'loess' mean

A.� Loess -�pronounced luss -�is German and means 'loose' or 'crumbly'. It is a gritty, lightweight, porous material composed of tightly packed grains of minerals.

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Q.� Why is loess significant

A.� Because it is so rich in minerals it makes very fertile soil and is very agriculturally very productive.

Also, loess is a rich source of information for scientists, since it provides a record of environmental change over thousands of years.

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Q.� How is loess formed

A.� Huge, heavy glaciers grind down rocks as they move over them to fine silt. This silt is then carried to the floodplain as the ice melts. The wind then picks up this fine silt and deposits it where it meets resistance against the valley walls.

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Q.� How deep can loess be

A.� There are two famous sites where the deposits are unusually thick. The Loess Hills in Iowa, USA are 200 feet high and 140 miles long. These are comprised of three layers, the youngest of which began forming 30,000 years ago, during the last Ice Age; most of the loess had been formed by around 14,000 years ago.

The other site, Shaanxi, China is much older -�formed 2.5 million years ago and thicker, up top 300 feet deep in places.

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by Lisa Cardy