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Terror in the Mountains
A What is incredibly beautiful yet absolutely terrifying and deadly at the same time? For anyone above the snowline in the mountains, there is little doubt about the answer. Avalanche – the word strikes fear into the heart of any avid skier or climber. For those unfortunate enough to be caught up in one, there is virtually no warning or time to get out of danger and even less chance of being found. The ‘destroyer of the mountains, avalanches can uproot trees, crush whole buildings, and bury people metres deep under solidified snow. Around the world, as more and more people head to the mountains in winter, there are hundreds of avalanche fatalities every year.
B A snow avalanche is a sudden and extremely fast-moving ‘river' of snow which races down a mountainside (there can also be avalanches of rocks, boulders, mud, or sand). There are four main kinds. Loose snow avalanches, or sluffs, form on very steep slopes. These usually have a “teardrop' shape, starting from a point and widening as they collect more snow on the way down. Slab avalanches, which are responsible for about 90% of avalanche-related deaths, occur when a stiff layer of snow fractures or breaks off and slides downhill at incredible speed. This layer may be hundreds of metres wide and several metres thick. As it tends to compact and set like concrete once it stops, it is extremely dangerous for anyone buried in the flow. The third type is an isothermal avalanche, which results from heavy rain leading to the snowpack becoming saturated with water. In the fourth type, air mixes in with loose snow as the avalanche slides, creating a powder cloud. These powder snow avalanches can be the largest of all, moving at over 300kmh, with 10,000,000 or more tonnes of snow. They can flow along a valley floor and even a short distance uphill on the other side.
C Three factors are necessary for an avalanche to form. The first relates to the condition of the snowpack. Temperature, humidity, and sudden changes in weather conditions all affect the shape and condition of snow crystals in the snowpack which, in turn, influences the stability of the snowpack. In some cases, weather causes an improvement in avalanche conditions. For example, low temperature variation in the snowpack and consistent below-freezing temperatures enable the crystals to compress tightly. On the other hand, if the snow surface melts and refreezes, this can create an icy or unstable layer.
D The second vital factor is the degree of slope of the mountain. If this is below 25 degrees, there is little danger of an avalanche. Slopes that are steeper than 60 degrees are also unlikely to set off a major avalanche as they ‘sluff® the snow constantly, in a cascade of loose powdery snow which causes minimal danger or damage. This means that slabs of ice or weaknesses in the snowpack have little chance to develop. Thus, the danger zone covers the 25- to 60-degree range of slopes, with most avalanches being slab avalanches that begin on slopes of 35 to 45 degrees.
E Finally, there is the movement or event that triggers the avalanche. In the case of slab avalanches, this can be a natural trigger, such as a sudden weather change, a falling tree or a collapsing ice or snow overhang. However, in most fatal avalanches, it is people who create the trigger by moving through an avalanche-prone area. Snowmobiles are especially dangerous. On the other hand, contrary to common belief, shouting is not a big enough vibration to set off a landslide.
Questions 1-5: Choose the correct heading for each paragraph A-E from the list of headings below (i-viii). There are more headings than paragraphs. Write your answers in the corresponding numbered boxes.
List of headings
i Examples of Major Avalanches
ii Stability of the Snowpack
iii What Sets Off an Avalanche?
iv An Expert's Comments
v Steepness of Mountains
vi Avalanche Peril
vii An Avalanche Risk Table
viii Types of Avalanche
1 Paragraph A
2 Paragraph B
3 Paragraph C
4 Paragraph D
5 Paragraph E
Questions 6-10: Complete the table below. Use NO MORE THAN TWO WORDS from the reading passage for each answer. Write your answers in the spaces provided.
Loose avalanches: also known as sluffs; steep slopes; (6) _____ shape; minor risk
Slab avalanches: thick layer of snow breaks off; set very hard once they stop; cause about 90% of (7) _____
Isothermal avalanches: caused by weight of (8) _____ mixed in with the snow
Powder snow avalanches: Develop a cloud of loose snow mixed with air; (9)_____ of all types of avalanche; more fast and cover a huge distance, even travelling (10) _____
A What is incredibly beautiful yet absolutely terrifying and deadly at the same time? For anyone above the snowline in the mountains, there is little doubt about the answer. Avalanche – the word strikes fear into the heart of any avid skier or climber. For those unfortunate enough to be caught up in one, there is virtually no warning or time to get out of danger and even less chance of being found. The ‘destroyer of the mountains, avalanches can uproot trees, crush whole buildings, and bury people metres deep under solidified snow. Around the world, as more and more people head to the mountains in winter, there are hundreds of avalanche fatalities every year.
B A snow avalanche is a sudden and extremely fast-moving ‘river' of snow which races down a mountainside (there can also be avalanches of rocks, boulders, mud, or sand). There are four main kinds. Loose snow avalanches, or sluffs, form on very steep slopes. These usually have a “teardrop' shape, starting from a point and widening as they collect more snow on the way down. Slab avalanches, which are responsible for about 90% of avalanche-related deaths, occur when a stiff layer of snow fractures or breaks off and slides downhill at incredible speed. This layer may be hundreds of metres wide and several metres thick. As it tends to compact and set like concrete once it stops, it is extremely dangerous for anyone buried in the flow. The third type is an isothermal avalanche, which results from heavy rain leading to the snowpack becoming saturated with water. In the fourth type, air mixes in with loose snow as the avalanche slides, creating a powder cloud. These powder snow avalanches can be the largest of all, moving at over 300kmh, with 10,000,000 or more tonnes of snow. They can flow along a valley floor and even a short distance uphill on the other side.
C Three factors are necessary for an avalanche to form. The first relates to the condition of the snowpack. Temperature, humidity, and sudden changes in weather conditions all affect the shape and condition of snow crystals in the snowpack which, in turn, influences the stability of the snowpack. In some cases, weather causes an improvement in avalanche conditions. For example, low temperature variation in the snowpack and consistent below-freezing temperatures enable the crystals to compress tightly. On the other hand, if the snow surface melts and refreezes, this can create an icy or unstable layer.
D The second vital factor is the degree of slope of the mountain. If this is below 25 degrees, there is little danger of an avalanche. Slopes that are steeper than 60 degrees are also unlikely to set off a major avalanche as they ‘sluff® the snow constantly, in a cascade of loose powdery snow which causes minimal danger or damage. This means that slabs of ice or weaknesses in the snowpack have little chance to develop. Thus, the danger zone covers the 25- to 60-degree range of slopes, with most avalanches being slab avalanches that begin on slopes of 35 to 45 degrees.
E Finally, there is the movement or event that triggers the avalanche. In the case of slab avalanches, this can be a natural trigger, such as a sudden weather change, a falling tree or a collapsing ice or snow overhang. However, in most fatal avalanches, it is people who create the trigger by moving through an avalanche-prone area. Snowmobiles are especially dangerous. On the other hand, contrary to common belief, shouting is not a big enough vibration to set off a landslide.
Questions 1-5: Choose the correct heading for each paragraph A-E from the list of headings below (i-viii). There are more headings than paragraphs. Write your answers in the corresponding numbered boxes.
List of headings
i Examples of Major Avalanches
ii Stability of the Snowpack
iii What Sets Off an Avalanche?
iv An Expert's Comments
v Steepness of Mountains
vi Avalanche Peril
vii An Avalanche Risk Table
viii Types of Avalanche
1 Paragraph A
2 Paragraph B
3 Paragraph C
4 Paragraph D
5 Paragraph E
Questions 6-10: Complete the table below. Use NO MORE THAN TWO WORDS from the reading passage for each answer. Write your answers in the spaces provided.
Loose avalanches: also known as sluffs; steep slopes; (6) _____ shape; minor risk
Slab avalanches: thick layer of snow breaks off; set very hard once they stop; cause about 90% of (7) _____
Isothermal avalanches: caused by weight of (8) _____ mixed in with the snow
Powder snow avalanches: Develop a cloud of loose snow mixed with air; (9)_____ of all types of avalanche; more fast and cover a huge distance, even travelling (10) _____
