Glaciation

In this section you'll revise:

  1. How to identify Glacial Features on a map.
  2. How to explain the formation of the main features of glaciation.

Some useful advice would be to take notes while you watch. Sometimes I'll draw diagrams, you'd do well to attempt to do the same as we go along and then put the labels on from memory after the clip has ended. You can always go back and re-watch it to see if you're right. Some people prefer to write the answer in full underneath the diagrams, others to label the pcitures, you need to find the way that is best for you.

Recognising Glacial Features on a Map

In this clip you can find out how to easily identify the most common features of glaciation.

In this video tour you can explore a glaciated environment. Make sure you get a 1:50,000 Fort William map so you can practise by matching the features I point out to the grid references. This will help you to see the link between the contours and the shape of the landscape. Pause at any time by clicking on the video and use the arrow keys to explore the landscape or investigate information points and pink balloons I've included in the tour. Use Ctrl+arrow keys to turn or look up and down. Have fun!

Corries

In this clip you'll revise how a corrie is made.

 

Aretes and Pyramid Peaks

As you'll have learned in teh Corrie Formation clip, these two diagrams can be attached to your understanding of how a corrie forms to explain how an Arete and a Pyramid Peak form.

U-Shaped Valleys

In these two clips I'll remind you about the main processes involved in the formation of a U-Shaped Valley.

 

 

Hanging Valleys and Truncated Spurs

Hanging valleys are easiest to understand as the product of a U-shaped valley. See if you can use this aerial picture to identify some truncated spurs and hanging valleys. The map underneath it matches the starting position of the aerial viewer.

 

Ribbon Lakes

Model answer:

Ribbon lakes are formed when a glacier advances and abrades the valley bottom. Where commpressional flow takes place erosion will be greater and if this happens over an area of softer rock the resulting differential erosion will deepen a hollow in the valley floor. When the glacier retreats repeated outpourings of melt-water will deposit layers of silt on the bottom of the hollow to form a lake bed of varves. The melt water will eventually fill in the hollow to form a ribbon lake which is typically long and narrow in shape.

Drumlins

There are different opinions to this one - therefore don't be surprised if you get taught something radically different!

Model answer:

As the advancing glacier carries englacial moraine it eventually slows and begins to halt and retreat as the climate warms. As it does so, it deposits the englacial moraine. It may build up around an obstacle that the glacier has been unable to erode such as a rock outcrop. As the glacier retreats its melt-water washes over the deposit of moraine and smooths it into a 'tear drop' shape. The stoss end will point towards the retreating glacier and the smooth lee towards the direction of melt-water flow. As a result of the way in which it is deposited the drumlin's moraine will be unstratified. Drumlins may occur in swarms as the glacier dumps large quantities of moraine at the same point.

Eskers

Eskers are a tricky feature to visualise. Watch this clip to further understand what is going on.

Model answer:

Eskers are formed where glacial melt water flowing across the surface of the ice flows down a moulin carrying till with it. This is then deposited under the glacier as sub-glacial streams flow under the ice towards the snout. This sediment and moraine builds up in layers so the esker is stratified. The meandering shape of the sub-glacial stream means that when the ice retreats due to the climate warming it reveals a snaking mound of well sorted moraine known as an esker.