Starter: Why is this Swiss valley floor so flat?

Glaciation – aims of the lesson:

• To know when the last ice age took place.

• To understand how and why glaciers form.

• To be able to explain how glaciers move.

• To use some geographical terminology.

Use an atlas to help you name the source regions of

the valley glaciers.

TASK 1: How much of the British Isles was covered in ice?

During this time temperatures fluctuated and ice advanced and retreated four times. The northern and eastern parts of the British Isles were covered in ice.

The Ice Age in Britain began about 1,000,000 years ago and lasted until about 20,000 years ago.

What is the glacier system?

The glacier system consists of inputs, transfers (flows), stores and outputs in the same way as a river.

Inputs come from avalanches along the sides of the glacier but mainly from precipitation as snow.

Over time snow accumulates and is compressed into ice. The water held in storage is the glacier.

Under the force of gravity, the glacier flows downhill.

Meltwater is the main output from the glacier, along with some evaporation.

Task 2: Draw diagram G from page 35.

Acccumulation and ablationThe balance between inputs and outputs varies.

In the winter, inputs usually exceed outputs near to the head of a glacier (accumulation).

In the summer and at lower altitudes, outputs will exceed inputs (ablation).

The balance between the annual rate of accumulation and ablation determines whether the glacier will advance or retreat.

Today, most of the world’s remaining glaciers are retreating.

Meltwater pouring from a glacier’s snout, SW Iceland

Zone of accumulation

Is the zone of accumulation at A or B?

B

A

Glacial Processes:

• Weathering – Freeze Thaw.

• Erosion - Abrasion. The moraine frozen into the glacier scours the valley sides and base. This is a sandpapering effect, similar to corrasion by a river but on a far larger scale.

• Erosion - Plucking. The water at the bottom of the glacier freezes onto rock on the valley base. As the glacier moves, the rock is pulled away from the valley base.

• Erosion – Meltwater. Ice tunnels of water that have melted.

• Shovelling or scooping. Collection of loose rock in the lower layers of ice.

To show you an example of an ice tunnel and some other glacial features, we’ll now watch a short clip from Born Survivor…

(from 4 mins to 10 mins 38)