WOW!!!

I wonder how this valley

was formed?

An introduction to Glaciation

Key Questions:1. What is a glacier2. Why study them?

What is a glacier?

• A glacier is a huge mass of ice resting on land or floating in the sea next to land, they usually move very slowly. A glacier acts in a similar way to an immense river of ice, often merging with other glaciers in a stream-like manner.

• Why are glaciers worth knowing about?

Glaciers are beautiful natural features

The action of glaciers produces some very distinctive landscape features

Pyramidal peakarete

Fjord

Melting glaciers might bring problems for us all!

What is a glacier?

• https://www.youtube.com/watch?v=k6gk1b4ACP0

Use an atlas to help you name the source regions of the valley glaciers.

Figure 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 are the main parts of a glacier?

Find a partner…

What is a glacier?

Key terms• Accumulation zone: area in the upper glacial valley where

new snow and ice forms.• Ablation zone: the loss of ice from a glacier due to melting.• Moraine: a mixture of rock and sediments left behind when a

glacier melts.• Bergschrund: A glacial crevasse (large crack) that forms when

the glacier pulls away from the stagnant ice above.• Tarn lake: when water collects in a depression in a glacial

valley.• Neve: new snow/ice that collects on a glacier. Snow and ice

that survives one season becomes known as firn.

Key terms1. _______: a mixture of rock and sediments left behind when a

glacier melts.2. _______: A glacial crevasse (large crack) that forms when the

glacier pulls away from the stagnant ice above.3. _______: when water collects in a depression in a glacial

valley.4. _______: new snow/ice that collects on a glacier. 5. Snow and ice that survives one season becomes known as

______

Bergschrund: A glacial crevasse (large crack) that forms when the glacier pulls away from the stagnant ice above.

Bergschrund: A glacial crevasse (large crack) that forms when the glacier pulls away from the stagnant ice above.

Tarn lake: when water collects in a depression in a glacial valley.

Moraine: a mixture of rock and sediments left behind when a glacier melts.

Make three annotated sketches for a tarn lake, a moraine and a bergschrund crevasse.

Look at the two photos.

What is different about them?

Can you think what might have caused them to be different?

Glaciers: Why are they called Nature’s Bulldozers?

To know why glaciers are called nature’s bulldozersTo know how glaciers change the shape of the land

Formation of a glacial trough

How does ice shape the land?

• Although Glacial ice appears solid it can behave like a fluid, when it pushes up against an object it is solid enough to erode it but fluid enough to move around it like water in slow motion.

• Melt-water lubricates the glacier and helps it to slip along the valley bottom, often refreezing around rocks and carrying them with it.

• This movement can change the shape of the valley in which the glacier moves.

A U-shaped glacial valley

V shaped valley formed by river erosion

GlacierCompressed snow

U shaped valley

lateral

vertical

Explain how ice shapes the land in no more than 20

words.

What is the difference between

erosion and weathering?

Erosion and weathering

• Erosion is the wearing away and removal of material

• Weathering is the action of the weather wearing away material in situ (where it is).

THREE images but what links do they have with GLACIAL

EROSION?

Plucking

Abrasion

Freeze thaw

Glacial Weathering/Erosion

There are THREE main types of glacial erosion: • Plucking

• Abrasion

• Freeze thaw

Task

1) Find a partner and sort yourself into the roles of TEACHER and STUDENT.

2) The TEACHERS will be shown three statements about each erosional pattern for 3mins only.

3) Using the knowledge recently gathered and the image the TEACHER needs to EXPLAIN what's happening with the THREE glacial erosional patterns (abrasion, plucking and freeze thaw) to the STUDENT.

• Freeze-thaw is a process of weathering that happens when melt water or rain gets into cracks in the bedrock (usually the back wall). At night the water freezes and expands causing a crack to get larger. Fragments may then fall under gravity.

• Plucking is when melt water from a glacier enters cracks in the rock. It then freezes to the glacier and base rocks. When the ice moves downhill, rock is plucked (pulled out) from the back wall and carried a long by the glacier.

• Abrasion is a sandpapering action. It happens when rocks in the base and sides of the glacier rub against the valley floor and sides as it moves. This wears away the rock, often leaving them with scratches.

• Plucking is when melt water from a glacier enters cracks in the rock. It then freezes to the glacier and base rocks. When the ice moves downhill, rock is plucked (pulled out) from the back wall and carried a long by the glacier.

• Abrasion is a sandpapering action. It happens when rocks in the base and sides of the glacier rub against the valley floor and sides as it moves. This wears away the rock, often leaving them with scratches.

• Freeze-thaw is a process of weathering that happens when melt water or rain gets into cracks in the bedrock (usually the back wall). At night the water freezes and expands causing a crack to get larger. Fragments may then fall under gravity.

Process Freeze-Thaw Abrasion Plucking

Diagram

Description

Make a copy of this table on a full page of your book, then complete the table.

Recap:

How does a glacier form?Re-arrange the following into the correct order

A. The residual snow settles, becoming more compact and dense.B. The great weight of the top layers compacts the deep layers.C. Snow falls.D. Annual snow accumulation far exceeds the annual snow melt.E. Compacted snow freezes together and creates sheets of ice.F. The number of layers increases.

C, D, A, F, B, E.

Processes operating in a glacial valley

• Erosion =

• Weathering =

• Transportation = • Deposition =

Breaking down of material by the action of the weather.

Movement of material from one place to another.

Wearing away of the rock and surface.

Putting down of material somewhere else.

Freeze Thaw weatheringArrange these into the correct order.

Draw a diagram(s) to show the process happening.

1. Eventually this continuous process causes rocks to break up.

2. As the water freezes it expands and causes the cracks to widen.

3. This cycle continues, each time widening the cracks.4. During the day when the sun is out, cracks in rocks get

filled with water as the glacial ice melts.5. The next time the temperature rises, the ice melts, the

water thaws and contracts.6. At night the temperatures become colder and the

water in the crack freezes.4, 6, 2, 5, 3, 1.

Abrasion is an important process of glacial erosion.Describe how it occurs. (3)

Abrasion uses material the glacier is carrying/transporting (1). This is from the surrounding valley sides (1) as a result of freeze thaw weathering (1)/plucking(1). The material is used to grind the sides and floor of the valley (1) like a sandpapering effect so that it is worn away (1).NEED ONE OF THE FINAL 2 POINTS FOR ALL 3 MARKS.

Upland glacial features (erosion)THE FORMATION OF CORRIES,

ARETES AND PYRAMIDAL PEAKS

Watch the video of the formation of a corrie and afterwards describe the

formation to a partner.

Erosional features: Pyramidal peaks, aretes and corries

http://www.youtube.com/watch?v=uYwGVVK3H2c

Now watch a second video that describes how the formation of a corrie(s) can lead to

the formation of aretes and a pyramidal peak. Use this information to explain the

diagrams on the next few slides.http://www.bing.com/videos/search?q=THE+FORMATION+OF+A+CORRIES%2c+ARETES+AND+PYRAMIDAL+PEAKS+AND+&view=detail&mid=3FA6AD43567F6AF0C2CF3FA6AD43567F6AF0C2CF&first=0&FORM=NVPFVR

Task 2• Design a cartoon strip to show the formation of a

corrie, arete and pyramidal peak. • Draw a simple diagram and write a short caption

underneath. e.g. Step 1: Snow gathers on a hillside and begins to

accumulate, eventually it becomes compacted and turns to ice.

Task 1• Add the names and definitions onto the worksheet:

Glacial mountain features.

Exam question - recapExplain the formation of a corrie (4 marks)

A corrie is an arm chair shaped hollow on a hillside. It is formed when snow and ice collect in a hollow.

The snow and ice move downhill under the force of gravity and the back wall of the hollow is plucked out and steepened.

The plucked material is carried by the glacier – it rubs against the base of the hollow and deepens it.

Ice is thinner at the front of the hollow and so there is less erosion – this leads to the development of a rock lip.

When glaciation is over and the snow and ice melt the corrie may fill with water forming a corrie lake (tarn lake)

A corrie is a bowl shaped depression in a glaciated landscape. The are found in the upper glacial valley.

Step 1: Snow gathers in a small hollow on a hillside – snow accumulates and eventually it becomes compacted and turns to ice.

Step 2: When the ice is thick enough it moves out of the hollow and down the slope under the force of gravity.

Step 3: As it moves it causes plucking at the back of the hollow – this steepens the wall of the hollow.Step 4: The plucked material is carried by the glacier. It rubs against the bottom of the hollow making it

deeper (abrasion).Step 5: Ice moves out of the hollow in a rotational manner – the thicker ice in the middle of the hollow

exerts a lot of pressure , giving very high rates of erosion.Step 6: At the front of the hollow the ice is thinner and there is less erosion – this means a rock lip is

left at the front of the hollow.Step 7: After glaciation has finished corries often fill with water – forming a corrie lake/tarn lake.

The formation of a corrie

Exam question:Explain the formation of a pyramidal peak 4 marks)

St Ivo School Geography Department 5413.08.03

Pyramidal Peak - formed where three or more corries intersect back to back, forming a sharp, pointed hilltop

between them

Mount Snowdon

Erosional features: fjords

A fjord is a long, narrow arm of the sea, often extending well inland, that results from marine inundation of a glaciated valley. Many fjords are remarkably deep; the huge glaciers that formed in these valleys were so heavy that they eroded the bottoms of the valleys far below sea level. After the glaciers melted, the waters of the sea invaded the valleys.

http://www.youtube.com/watch?v=y0pvswzqCX0

Lower glacial features of erosion: Fjords

1. What is a fjord?2. How does it form?

Features of deposition - Moraine

Types of moraineMaterial found along the edge of

a glaciated valley is called lateral moraine.

If two glaciers meet, their lateral moraines join together forming medial moraine. This leaves a line up the centre of the valley.

A terminal moraine is a ridge of material deposited at the front of the glacier marking the furthest point the glacier reached down the valley.

Erratics

Drumlins