When a glacier moves through a valley it exerts a tremendous force on the hillsides. The friction, or rubbing, of the ice mass is also increased by the large number of rocks which are frozen fast inside it and which act as abrasive or scouring elements. The glacier therefore scoops out great masses of soil and rock. When it has retreated or melted the marks of the rubbing or abrasion can be seen on the rocks. These rocks have rounded tops and are known have rounded tops and are known as roches moutonnees, which means ‘rocks shaped like sheep’. These rocks show heavy scratches known as striae, caused by the rubbing force of the glacier.

Glacier valleys can also be recognized in another way. In a river valley the flow of water is concentrated at one part of the valley’s floor, so that a river valley is V-shaped. In a glacial valley the glacier is spread out all over the valley floor and a glacial valley is U-shaped.

Examples of glacial valleys include the fjords, the long sea inlets, of Norway. The sea now fills these long narrow bays but at one time they were completely locked in ice.

To the north of glacial valleys where the great glaciers are formed as a result of accumulation of snow, there are cirques. These are vast hollows scooped out of the side of hills or mountains by ice and snow when they melt and fall away. In Scotland cirques are known as corries and in Wales as cwms. Sometimes two cirques are formed together and separated only by a narrow ridge called an arête.