1. What is an avalanche?
Lesson objectives:
To understand what causes avalanches
To understand what effects they have
on people.

2. Homework
• Revise for a test next lesson on all you
have learnt on glaciation so far.
LO : What is an avalanche?

3. What causes an avalanche?
• Watch this video to find out
LO : What is an avalanche?

4. What is an avalanche?
Which do you think is the correct definition, make your choice, check with
your teacher, and write the correct definition in your book.
A rapid flow of snow down a slope. It can be set off by a natural
event, such as lots of fresh snow fall, or by human activities, such
as people ski-ing off piste, walking or climbing.
A landslide that moves at great speeds, taking out everything in it’s path.
A tsunami of snow that wipes out moves slowly down the mountain until its
momentum increases and then it produces a cloud of white powder that means you
cannot see anything around you.
Skier triggers avalanche

5. What causes an avalanche?
• Stick your picture of an avalanche in the
middle of the page.
• With the person next to you, use the
information sheet to find five key causes
of avalanches….there are red-herrings, so
you need to use your common sense to
work out which are the right answers.
• The resources you need to use are on the
next slide.
LO : What is an avalanche?

6. Snowfall – avalanches usually happen within 24hours of heavy
snow. The risk is greater with over 30cm of snowfall.
Businesses – avalanches usually happen when local ski
businesses open up their ski hire shops for the winter season.
Temperature – avalanches usually happen when a large rise in
temperature is seen as this can cause weaknesses in the upper
layers of snow.
Tourists – avalanches usually happen when Easy jet offer cheap
flights to mountainous destinations in the winter months,
encouraging tourists to visit.
Wind direction – avalanches usually happen when wind blows
up the windward side of the mountain and drops it on the
leeward side. This can cause an uneven build-up of snow on the
leeward side, which is more likely to avalanche.
Steepness – most avalanches occur with an angle between 30
and 50°.
Ski-ers – avalanches usually happen when ski-ers call loudly
across the mountains, to attract the attention of their fellow ski-
ers!
Slope shape – avalanches are more likely to occur on
convex rather than concave slopes.
LO : What is an avalanche?

7. What are the effects of
avalanches?
LO : What is an avalanche?
Short term effects Longer-term effects

8. Sort it out!!
The number of tourists can fall, due to fear and the loss of facilities
Restaurants and hotels might be destroyed or have to close
If people are caught in an avalanche they’re likely to be killed straight away – or buried
in the snow and suffocated
Local businesses, such as shops , ski-hire and tour guides will lose money
If businesses are forced to close, this can lead to long term unemployment
If people survive, they’ll almost certainly be seriously injured and have broken bones
Buildings in the path of the avalanche will be flattened or buried
Roads are often blocked which slows down the rescue efforts

9. Final round-up
• Put the following statements in order;
1. Loss of life,
2. Damage to the economy,
3. Loss of jobs,
4. Fewer tourists,
5. Damage to village
LO : What is an avalanche?

10. Plenary Video
• Watch this and see what happens when
an avalanche rescue goes a bit wrong!
LO : What is an avalanche?