What are glaciers?

• The last Ice Age ended 10,000 years ago
• Today only 10% of the earth is covered by ice sheets, ice caps and valley glaciers
• A glacier is like a very slow moving river of ice
• They are formed in areas of high snowfall in winter and cool temperatures in summer.
• This means that the snow that accumulates in the winter and isn't lost by melting or evaporation during the summer.
• These conditions occur in polar and high alpine regions.
• There are two main types of glaciers: valley glaciers and continental glaciers.

How does a glacier form?

• A glacier forms when snow accumulates over time
• The snow becomes compressed under the weight of more snowfalls 
• This turns the accumulated snow to ice
• The ice becomes even more compressed and air is forced out
• The ice crystals become larger as the air spaces become smaller and this turns the ice blue!
• Eventually the combined weight of the ice and the force of gravity forces the ice to start moving (very slowly of course)

Key points

• A glacier is an open system with inputs, flows, stores and outputs
• The balance between accumulation (how much snow enters the glacier) and ablation (how much is melted) determines whether a glacier will move forward (advance) or move backwards (retreat)
• The front end of the glacier is called the snout
• Frost shattering is a type of physical weathering
• Plucking and abrasion are processes of glacial erosion
• There are five features of erosion
• There are three main features of deposition

This video looks at Glaciation in action