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INT D 280 > Hazards > Flashcards

Hazards Flashcards

1
Q

What are avalanches?

A

The sudden release and movement of vast amounts of snow down a mountainside under the influence of gravity.

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2
Q

What historical factors contributed to avalanche problems in the European Alps between the 16th and 18th centuries?

A

Increasing population and the widespread cutting of mountain forests coincided with the increasing snowfall and glacial advance of the Little Ice Age.

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3
Q

What was one of the greatest avalanche disasters in Europe during the First World War?

A

A series of enormous snow slides on the Austrian-Italian front killed 10,000 soldiers in a single day.

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4
Q

When did the first major problems with avalanches arise in North America?

A

During the 1800s Gold Rush era, when prospectors flooded into the mountain West, and numerous mining towns were established.

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5
Q

When did the earliest recorded avalanche fatalities in Canada occur?

A

In 1782, when 22 people from an Inuit settlement near Nain, Newfoundland and Labrador, perished.

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6
Q

Where did the deadliest avalanche in Canada occur?

A

In Rogers Pass, at the height of the Colombian Mountains in BC: On March 4, 1910, 58 workers were killed as they were clearing a section of railway.

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7
Q

Define snowpack.

A

When snow falls in mountains, it accumulates in layers within the snowpack, which is the total amount of snow on the ground.

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8
Q

What influences the stability of snowpack?

A

How well the different layers of snow adhere to one another and the surface on which they fell.

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9
Q

What is the term for the bond and anchorage of snow layers that resists the downslope force of gravity?

A

Shear strength.

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10
Q

What happens when shear stress outweighs shear strength?

A

An unstable mass of snow breaks loose, creating a snow avalanche.

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11
Q

What are sluffs?

A

Avalanches range in size from small sluffs that wouldn’t harm a person to large powerful slides capable of destroying forests or even small villages.

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12
Q

What are the two principal types of snow avalanches?

A

Loose-snow avalanches and slab avalanches.

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13
Q

What are loose-snow avalanches sometimes called?

A

Point-release avalanches, because they start when a small amount of loose snow slips and begins to slide down a slope, setting additional snow in motion.

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14
Q

Describe loose-snow avalanches.

A

Initiate at a point, tend to grow wider as they slide, occur much more frequently in freshly fallen snow on steep slopes, generally shallow, small, and cause little damage.

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15
Q

When do slab avalanches occur?

A

When a plate or slab of cohesive snow begins to slide as a unit before breaking up.

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16
Q

What four things do you generally need for slab avalanches?

A

A slab of snow (typically dense mass), weak layer (less cohesive strength) beneath, steep slope (>30), and a trigger.

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17
Q

What can trigger failure in sensitive weak layers below slab avalanches?

A

Most avalanches are triggered when slopes are loaded by additional or new snow. Natural triggers can include warming temperatures, rain, rock fall, cornice failure, or earthquakes.

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18
Q

On what slopes do the majority of avalanches occur?

A

On slopes between 36-39 degrees; slopes greater than 60 degrees usually are too steep to hold snow.

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19
Q

What is a crown in avalanche terminology?

A

The area of release marked by a distinctive upper fracture line, or ‘crown’, which is perpendicular to the slope and extends down to the sliding surface, or ‘bed surface’.

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20
Q

What are the three major sections or zones of avalanche paths?

A

Starting zone (uppermost part), track (avalanche travel area), runout zone (where debris accumulates at bottom of slope).

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21
Q

What speeds can dry slides reach?

A

Dry slides can reach speeds of 50 to 200 km/hr.

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22
Q

What happens when dry flowing avalanches exceed 35 m/hr?

A

A dust or powder cloud of airborne particles of snow is created and moves above the dense flowing part of the avalanche.

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23
Q

Why can the violence inside flowing debris grind up snow into finer particles?

A

Small grains sinter much more quickly than large, and the tiny grains making up avalanche debris can sinter as much as ten thousand times faster than the larger grains of the initial slab.

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24
Q

What are wet-snow avalanches characterized by?

A

They tend to slide at much slower speeds with no dust cloud, but their impressive mass can still cause great damage.

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25
Who is Jeff Goodrich?
Jeff Goodrich is Senior avalanche forecast with Parks Canada, overseeing 134 avalanche paths within a 40 km stretch of highway.
26
What are landslides?
The downslope movement of rock and debris.
27
When do landslides occur?
When shear stress with a slope outweighs the shear strength of the slope’s rock or sediment layers, causing the slope to fail.
28
How does vegetation on a slope increase its shear strength?
Acts as a barrier to slow downslope movement and acts as a natural anchor for soils.
29
What decreases the shear strength of a slope?
Slopes with smooth surfaces, like rock, have low frictional strength, making them slippery, and adding a lubricant (i.e. water).
30
What are other ways to decrease slope stability?
Streams and rivers undercutting slopes, and human activities such as clear-cutting forests, mining, road construction, and home building can undercut or overload slopes.
31
How are different types of landslides classified?
By their material composition, their water content, and how they move down a slope.
32
How do rockfalls occur?
When rocks suddenly detach from slopes; rockfalls occur when a rock detaches and falls freely, while topples occur when a large piece of bedrock falls off a slope and rotates end-over-end.
33
Where do rockfalls and topples usually occur?
On steep slopes with exposed bare rock, often triggered by rain or freeze-thaw cycles.
34
What is an example of a significant rockfall?
Turtle Mtn, S Rockies AB, near the Crowsnest Pass, where approximately 82 million tons of limestone fell into the valley below in 1903.
35
What factors led to the rock slide of Turtle Mtn?
Unstable geology, water seepage into underlying limestone, freeze-thaw cycles, and instability due to erosion from glaciers and the Crowsnest river.
36
When do translational and rotational slides occur?
When a plane of weakness in the rock or sediment causes an overlying consolidated mass to move downslope along the surface of the rupture.
37
What is a distinguishing feature of translational and rotational slides?
A steep 'head scarp', a nearly vertical region of exposed soil and rock at the head of the landslide.
38
What is another name for a rotational slide?
Slump.
39
What are earthflows?
Earthflows involve the fluid-like movement of fine sediments downslopes.
40
When do earthflows occur?
When slopes made of unconsolidated sediments become water-saturated.
41
What are 'earth creeps'?
Very gradual downslope movements when little water is present.
42
What are debris flows?
Similar to earthflows but composed of larger sediments, such as rocks and boulders, making them the most dangerous type of landslide.
43
What are the most dangerous type of landslides?
Debris flows.
44
What features characterize debris flows?
Usually triggered by a large influx of water, happen quickly, are fast-moving, and can travel far.
45
Where do debris flows often follow?
The courses of mountain streams and rivers.
46
What are some methods used to mitigate damage caused by landslides?
Rockfall shelters or tunnels, drape nets across vertical cliffs, catchment fences, levees along streams prone to debris flows, and diversion structures.
47
What methods are used to prevent landslides from happening?
Metal anchors in mountainsides, ditches, culverts, drains for drainage, and tree planting to stabilize slopes.
48
How are magma types defined?
By their silica content.
49
What does the amount of silica in magma determine?
Its viscosity.
50
What does low silica content mean?
Low silica = low viscosity. E.g. Basaltic magma.
51
What does high silica content mean?
High silica = high viscosity = higher resistance to gradual deformation. E.g. Rhyolitic magma.
52
What is an example of basaltic magma found in hotspots?
Svartifoss waterfall, Skaftafell National Park, S Iceland.
53
What does viscosity influence?
The shape of the volcano and how easily gas that is trapped in magma can escape.
54
What are shield volcanoes?
Volcanoes produced by basaltic magma with low viscosity lava creating broad, gentle sloping volcanoes.
55
Give an example of shield volcanoes.
The Hawaiian and Galapagos Islands; or Tamu Massif.
56
What are stratovolcanoes (composite volcanoes)?
Produced by rhyolitic magma with high viscosity lava that forms steep conical slopes.
57
What is an example of explosive eruptions?
Krakatoa, Vesuvius.
58
What are Stratovolcanoes (Composite Volcanoes)?
Produced by rhyolitic magma. The high viscosity lava does not spread far resulting in piles, forming steep conical slopes. Also traps gas, causing internal pressure to build, explosive eruptions.
59
Give an example of explosive eruptions.
E.g. Krakatoa (catastrophic eruption in 1883); Vesuvius (destroyed Pompeii and Herculaneum in 79 AD); Mount Saint Helens; Mount Pinatubo.
60
What are lava flows?
When lava pours out of a volcano and moves downslope. Destroy everything in their path; almost impossible to stop.
61
What is the least hazardous volcanic process?
Lava flows, because usually not-life threatening, slow.
62
Give an example of lava flows.
E.g. Eruption of Kilauea forms part of Hawaii has been ongoing since 1983, resurfaced over 125 km square land, buried about 14 km of highway and destroyed over 200 homes.
63
How is volcanic ash produced?
Through explosive eruptions. When gas explodes out of magma, the magma is shattered and propelled into the air where it cools and solidifies into very small shards of glass and rock. Therefore, volcanic ash is heavy and abrasive.
64
If volcanic gas is projected high enough…?
It can reach stratosphere, upper layer of Earth’s atm. It can travel thousands of km, have far-reaching effects. ## Footnote It can produce ash clouds that block incoming solar radiation and can have temp cooling effect on Earth.
65
Volcanic ash can coat everything, destroying infrastructure and crops. Give an example.
E.g. The April 2010 eruption of Eyjafjallojokull in Iceland severely affected air traffic in Europe costing the aviation industry almost 3 billion. Grounded airplanes across Europe for a week, stranding millions of airline passengers.
66
What happens if volcanic ash is inhaled?
It causes breathing problems and can lead to suffocation.
67
What are pyroclastic flows?
When hot masses of gas and rock fragments are ejected and move downslope. Compared to lava flows, pyroclastic flows are much more dangerous: they travel downslope fast, reaching speeds of up to 700 km/hr and reach 100s of degrees. Thus are difficult to escape from.
68
Give an example of pyroclastic flows.
E.g. The deadly 1902 eruption of Mount Pelee, on the island of Martinique in the Caribbean, created pyroclastic flows that buried the town of St. Pierre, killing 30,000 people.
69
What are lahars?
The height of many volcanoes means that they are often covered in snow and glaciers, and the heat of an eruption can cause them to rapidly melt with catastrophic consequences. The melting snow and glaciers can create a volcano-triggered version of a debris flow.
70
How are lahars triggered?
When the large amounts of water released from the melting snow and ice mix with the loose volcanic rock and ash on the flanks of the volcano. This mixture pours into creeks and rivers as wet cement, and they are often hot, causing burn injuries to their victims.
71
Lahars are not as ___ as pyroclastic flows but, like other downslope hazards, they bury and destroy everything in their path.
Fast.
72
Lahars don’t require a large eruption to be triggered. Give an example.
E.g. One of the greatest lahar disasters occurred in 1985, when Nevado del Ruiz erupted in Colombia. Although not a large eruption, it melted the volcano’s summit glaciers and triggered a series of lahars that ran down the rivers. These lahars destroyed several communities built along the rivers and killed approximately 23,000.
73
What is a potential hazard when volcanoes erupt near water?
The displacement of large volumes of sea water, which can generate large waves called tsunamis.
74
Give an example of a tsunami generated by a volcanic eruption.
E.g. the 1883 eruption of Krakatau in Indonesia created massive tsunamis that inundated the surrounding coastal areas, killing 36,000.
75
What is perhaps the greatest impact that volcanic eruptions have had throughout history?
Their release of gas into the atmosphere.
76
What are two gases ejected during an eruption that have important impacts on Earth’s climate?
1. CO2 2. Sulphur Dioxide
77
Why is CO2 important?
Greenhouse gas. Recall: Earth itself is the source of most of the Planet’s heat. It traps incoming solar radiation and radiates heat back into the atmosphere. The heat that is radiated from the Earth is then reabsorbed by greenhouse gases in the atmosphere, which lock in heat.
78
How do greenhouse gases regulate the Earth’s climate?
Without them, the Earth would be too cold to support life. However, the concentration of greenhouse gases in the atmosphere is a delicate balance, and volcanoes have been essential to maintaining this balance over the 4.5 billion years of Earth’s history.
79
What is the cycle of CO2?
CO2 sequestered in plants through photosynthesis into tissues. Buried in Earth and carbon sequestered into coal beds and rocks. Subducted into mantle, CO2 released into magma where it erupts back into atmosphere.
80
How does sulphur dioxide affect Earth’s climate?
It reacts with water vapour to produce sulphuric acid. Sulphuric acid then falls to Earth as acid rain, which can have harmful impacts on plants, animals, and human health. The corrosive nature of sulphuric acid causes the outsides of buildings to deteriorate and disintegrate.
81
What happens if sulphur dioxide reaches the stratosphere?
Like volcanic ash, if explosive enough, it can travel widespread and can stay aloft for several years. The high albedo of sulphuric acid reflects incoming energy, which can cause temperature cooling of the Earth’s climate. Decreased global temperatures caused by sulphuric acid, and to a lesser extent volcanic ash, is called a 'volcanic winter.'
82
Give an example of a volcanic winter.
E.g. Volcanic winter following the 1991 eruption of Mount Pinatubo, Philippines, 2 years following average global temperature fell by almost 1 degree.
83
What stunning sunsets can volcanic winters produce? Give an example.
E.g. Fantastic skies in Edvard Munch’s famous painting 'The Scream' inspired by sunsets created by the 1883 eruption of Krakatoa.
84
What is the biggest hazard associated with winter mountain travel?
Avalanches.
85
What are the 5 key things to remember in avalanche terrain?
1. Get the gear (avalanche transceiver, probe, shovel, as minimum, avalanche airbag backpacks, helmet) 2. Get the training 3. Get the forecast (Avalanche forecast) 4. Get the picture (Be aware) 5. Get out of harm’s way.
86
What is Tamu Massif?
A large underwater volcano located in the NW Pacific Ocean, east of Japan.
87
What was the impact of the 1883 eruption of Krakatoa?
Killed 36,000 people.
88
What was the impact of the eruption of Mount Pinatubo?
Decreased global temperatures by 0.5 degrees.
89
What was the worst volcanic disaster of the 20th century?
The eruption of Mount Pelée in Martinique, which destroyed St. Pierre and killed 30,000 people.
90
What is Paricutin?
A cinder cone volcano located in Michoacán, Mexico.
91
What is Mount St. Helens known for?
Located in Washington, USA, it is part of the Cascade range.
92
What is Eyjafjallajökull?
A volcano in Iceland covered by an ice cap.
93
What is Turtle Mountain known for?
The 1903 Frank slide that killed 70 people, known to Blackfoot and Ktunaxa as 'the mountain that moves.'
94
What was the Armero tragedy?
A lahar disaster caused by the eruption of Nevado del Ruiz in Colombia, killing approximately 25,000 people.
95
What is the documentary 'A Dozen More Turns' about?
A 2005 documentary about backcountry skiing, avalanches, and how the 'human factor' can have dire consequences. Based on a true story about 5 friends that ends in powerful lessons and unfortunate tragedy.
96
What happened during the avalanche on Mt Nemesis?
It involved surface hoar, frozen dew.

INT D 280 (2 decks)

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