1. Introduction to Course: Welcome Back and congratulations on your AS Grades.

The A2 Course is made up of 3 units (Unit 4 - Physical Systems, Processes and Patterns; Unit 5 - Human Systems, Processes and Patterns and Unit 6 - Synoptic: People and their environments. See summary diagram of course for relative weighting of the AS/A2 assessments for your final grade.

2. Introducton to Glacial Systems (Unit 4.2)

GLACIER FORMATION AND THEIR DISTRIBUTION

(i) What are Glaciers?

Glaciers are moving bodies of ice, formed by the accumulation of snow on the ground's surface. Glaciers are powerful agents of erosion, transport and depostion that are able to shape the landscape and create spectactular landscapes. The term 'glacial' refers to the work of ice and metwater in shaping the landscape.

(ii) How do Glaciers form?

Glaciers form when accumulation (i.e. winter snow fall) is greater than ablation (summer melting). Where temperatures in the summer remain cool and allow some snow to remain on the ground, further snow fall the following winter can result in the accumulation of further layers of snow. As these layers become thicker and denser, eventually ice is formed (see summary below)

(iii) The formation of Ice / Glaciers

• Where temperatures are cold enough, snow will fall, if temperatures remain freezing, snow accumulates on the ground;
• Where summer temperatures are low (little ablation), a permanent snowfield may begin to form;
• When further snow falls on top of previous layers, air is trapped (initially there is a low density ~0.1g/cm3)
• As snow continues to accumulate, the pressure of the compaction is able to gradually force air out, turning the snow layers to ice (diagenesis)
• Gradually densities increase to around ~0.5g/cm3 at which it is known as firn ice / neve (transition between snow and ice)
• Gradually the increased pressure may cause some melting within the snow, this meltwater then refreezes in the gaps between ice crystals further increasing the density;
• Overtime / with increasing depth, the density of the ice reaches ~0.9g/cm3 at which state it is known as true glacial ice

When the weight / resulting pressure is great enough, the ice will begin to 'flow' downhill, forming a glacier.

(iv) The Past Distribution of Glaciers

• Areas of glacial activity expand and contract due to climate change;
• The earth has experienced a number of major periods of ice activity ('ice ages' / 'glacials') - roughly every 200-250 million years.
• The last ice age ended 10,000 years ago. The ice was at its maximum extent around 18,000 years ago and covered the UK in the north and as far south as the British Channel and Norfolk.

Picture source: University of Birmingham (Shotton Project) - picture linked to site

Lesson Resources (Handouts and Extra Links)

Links:

Link to detailed course specification (Edexcel Geography 'A') (pdf file)

Handout:

Summary of Autumn/Winter Plan for A2 Lessons (pdf file)

Suggested Background Reading:

What is a Glacier? (external link)

How a glacier forms (external link)

Ice Age Britain (Radio 4 Broadcasts) - may need Broadband (available in school) for this

Causes of Glaciation (external link)

The Last British Ice Sheet - A review of the evidence used in the compilation of the Glacial Map of Britain (Durham University 2005)