CORE UNIT: PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT
As the ice moves downhill it may move at different speeds over the landscape, causing huge cracks called crevasses to open and close on the surface of the ice. Imagine bending a chocolate-covered caramel bar slowly; the base stays connected but the chocolate surface cracks.
Fig. 6 Deep crevasse in ice
Fig. 7 These tunnels in a glacier at Mer de Glace in France are a tourist attraction. New tunnels are made each year as the ice moves downhill from the entrance ramp.
9.4 Types of glaciers
The accumulation of ice starts in hollows called corries high up in the mountains. This glacier type is called a cirque or corrie glacier. In Ireland Upper and Lower Lough Bray, CountyWicklow contained corrie glaciers. The continued accumulation of snow and icemakes the glacier build up inside the
Cirque glacier
corrie until it spills out of the hollowand down into the valley below,where it is now called a valley glacier, for example the Lough Bray corrie glaciers spilled down into the Glencree Valley below. Valley glaciers are very common in the Alps today. As valley glaciers advance onto lower lying land they meet and merge together to form a piedmont glacier.
In
Valley glacier
Piedmont glacier
Wicklow glaciers from the Glencree, Glenmacnass, Glendalough and Glenmalure valleysmet and covered the land from the mountains to the sea. Sometimes glaciers get so large
Fig. 8 Different types of glaciers 144
that they cover whole continents and seas. They are then called ice caps or ice sheets. During the last ice age the ice sheet from the Arctic joined up with the valley and piedmont glaciers covering Ireland and much of North Europe.