Glacial Processes
Uploaded by Admin on Feb 12, 2001
There are many different glacial landforms created by glacial erosion, one of these landforms is U-shaped valleys or glacial troughs. This glacial landform has many distinct characteristics. One of these characteristics is that it has very steep valley sides caused by the glacier as it moves down the valley eroding the sides of the valley by the processes of abrasion and plucking. Abrasion is when the boulders and moraine carried by the glacier rubs and erodes the valley side as it physically moves down the valley. Plucking happens when the water in the glacier freezes inside of the cracks in the individual rocks on the valley side then the water freezes and as the glacier moves the rock is plucked or torn from the valley side producing the steep side to the valley.
The valley also has wide flat floors caused by ice movement aided by large volumes of melt water and moraine has greater erosive power than that of rivers. This results in the wide floors. The greater erosive power of the glacier than that of a river also causes the valley to be very straight compared to the valley shape that a river has eroded, it has no interlocking spurs because the shear power of the glacier has slowly smashed through the original spurs of the valley. Just before the glacier forms and when the temperatures are cold enough known as the the “pre glacial” period the process of freeze thaw takes place, this aids the formation of the u shaped valley. Freeze thaw is when the water in the summer enters the cracks of rocks and the in winter when the temperatures have gone below 0 degrees centigrade the water freezes in the cracks and because when water has frozen the particles in the water have less movement and expand causing the rock to shatter. Freeze thaw therefore helps in the formation of the u shaped valley by breaking up the valley floor so that the floor is weakened so the glacier can easily and speedily erode the valley floor by all the conventional forms of erosion like plucking abrasion but with greater ease.
There are many of examples of u shaped valleys around the world because wherever there has been a glacier there will be a u shaped valley that has been formed as it moves down the valley. One example of a u shaped valley is that...