Glaciation - Unit 8 Flashcards
(46 cards)
What is an avalanche?
Falling masses of snow that can contain rocks, soil or ice
What are the 6 possible trigger mechanisms for an avalanche?
1- Sudden increase in temp
2- Heavy rain
3- Long, cold, dry winter
4- Human factors, e.g. vibrations from skiing
5- Deforestation
6- When warm atlantic air meets cold polar air = heavy spring snow fall
Where do avalanches impact on human activity?
- Global skier destinations
How many skiers are attracted to mountain ski resorts each year?
300 million
Which mountain range will have the largest number of skiers?
Switzerland - the Alps
On average, how many people die from avalanches each year?
40
Of the 40 people that die from avalanches each year, what percentage of them were involved in winter sports?
80%
What are the impacts of avalanches on human activity?
1- Deaths/injuries
2- Property damage - pressure to expand villages and recreational facilities in mountain areas has increased
What is the annual property loss to the USA?
$1 million USD
What is the annual property loss to Switzerland?
$20 million USD
Describe 4 management strategies that can be used to manage avalanches
1- Closing avalanche prone slopes
2- Trigger small avalanches - before the snowpack builds to a dangerous state. These ‘artificial’ avalanches are triggered remotely by small fires from a large gun
3- Controlling avalanche activity - stabilising snow pack in starting zone (wedges), planting trees & building walls
4- Planning - where not to build in mountain areas
Name an avalanche case study
The Galtur avalache, Austria
When was the Galtur avalanche?
February 1999
Describe the Galtur avalanche
- A powder avalanche
- Snowfall in preceding days had exceeded all records, with more than 4m of snow lying on slopes
- 170,000 tonnes of snow involved in initial movement
- Travelled at 200 miles per hour
Give 3 impacts of the Galtur avalanche
1- 31 people died, 26 tourists, 5 locals
2- 16 buildings destroyed
3- Ski resorts closed in region, costing the industry £5 million for each day they were closed
What does GLOF stand for?
Glacial Outburst Floods
Where can a GLOF occur?
- Where a terminal/recessional moraine acts as a dam for glacial meltwater
- Behind the moraine a pro-glacial lake develops
- If the lake overtops the dam or the dam gives way, a torrent of floodwater will cascade down the valley
Give 7 potential triggers of wave generation
1- Contact glacier calving 2- Icefall from hanging glaciers 3- Rock/ice/snow avalanches 4- Dam settlement and/or piping 5- Ice-cored moraine degredation 6- Rapid input of water from supra-, en-, or subglacial sources 7- Seismic activity
Give 4 conditioning factors for dam failure
1- Large lake volume
2- Thin dam wall
3- Melting of buried ice in moraine structure
4- Low point in dam wall
What are the 3 common key stages of a GLOF?
1- Formation of displacement waves in lake
2- Dam failure
3- Resultant flood wave down-valley
Name a GLOF case study
Bhutan. a small mountainous, undeveloped kingdom located in the eastern Himalayas
How many potentially dangerous lakes are in Bhutan?
25
Give an example of a dangerous lake in Bhutan
Thorthomi Lake
Why does lake Thorthomi pose a threat?
- Several supraglacial ponds on Throthomi glacier are growing quickly and merging
- Their proximity to other large glacial lakes causes a threat
