Chapter 6 Flashcards
What tectonic environment is NOT associated with volcanic activity?
- transform fault boundaries
In Canada, volcanoes are found in the following techtonic environment, except:
- transform fault boundaries
Where are Canadian volcanoes located?
- British Columbia, Yukon
The country of ____ is a volcanic plateau built of basaltic lava erupted from a hot spot underlying the Mid-Atlantic Ridge in the North Atlantic Ocean.
- Iceland
Place the following volcanic hazards in order of their deadlines, with the most deadly process at the top and the least deadly process at the bottom.
1) pyroclastic flows
2) tsunami
3) lahars
4) gas
5) lava flows
A _____ is a mudflow composed of volcanic debris that is fluid when moving, but solidifies soon after stopping.
- lahar
A scientist determines that ‘crystal volcano’ is 5,000 years old. What can the scientist assume about the ages of three other nearby volcanoes?
- if the volcanoes were created by a hot spot, the ages of the other volcanoes depend not he order of crystal volcano in the sequence
- if the volcanoes were created by subduction, they are likely to be about the same age
If there was a large volcanic eruption in the cascade range, which flight could be affected by volcanic ash?
- Edmonton to Vancouver
Some phenomena that may be used to predict volcanic eruptions include ____.
- seismic waves
- ground deformation
- gas emissions
Which gas was ultimately responsible for the deaths of thousands of villagers near Lake Nyos, Cameroon, in 1986?
- carbon dioxide
Lava flows are rarely responsible for many volcano related deaths because they ____.
- move too slowly
A pyroclastic flow _____.
- can move at speeds that exceed 100 m/sec.
- is a mixture of magma, volcanic ash and gas, and air
- can reach temperatures of 350 celsius
How did the population of Heimaey, Iceland, take advantage of the lava flows that nearly destroyed their harbour?
- installed pipes to pump water through the slowly cooling lava, creating their own thermal heating system
How do hot spots and tectonic plates move relative to each other?
- hot spots are static relative to tectonic plates
Long, linear ____ eruptions composed of low-viscosity, low-volatile lava flows are typical in the country of Iceland.
- fissure
Place the vents of the eruptive sequence of the 1980 Mount St. Helens in order of their occurrence, with the oldest event at the top and the most recent event at the bottom.
1) rising magma begins to reshape Mount St. Helens, setting off a series of earthquakes
2) the volcanic bulge on Mount St. Helens collapses, generating an avalanche
3) a drop in pressure on the side of Mount St. Helen’s creates a pyroclastic flow
4) rapid escape of volcanic gases blew magma upward, generating a psi naan eruption phase on Mount St. Helens
Which of these hazards, associated with Mount Baker, could affect Vancouver?
- Lahar
- large quantity of volcanic ash
What happens to rising magma in subduction zones?
- the magma becomes enriched in silica (SiO2)
- the magma melts the overlying crust
Subduction zones volcanoes affect humans more than any other type of volcanic activity because ____.
- the areas around subduction zone volcanoes are often heavily population
- they eject material directly into the atmosphere, causing short-term changes in climate
Undersea volcanic eruptions are one culprit int he formation of ____, which are the second most deadly volcanic process.
- tsunami
What is the dominant deformation force that created a large crack on the seafloor?
- tension
The potential hazards of volcanic eruptions are extensive and include
- tsunamis
- lahars
- lava flows
- poison gas
Which of the following is a primary volcanic hazard related to the interaction between lava and ice?
- Jokulhlaup
One of the most dangerous phases of a volcanic eruption occurs when ____.
- less energy is fed into the eruption column, causing it to collapse and sending pyroclastic flows down the flanks of the volcano.
The 1816 “Year Without a Summer”, during which global temperatures were well below average, was the result of short-term climate changes cause debit he eruption of _____ volcano.
- Tambora
Partial melting of rock in subduction zones is aided by the addition of ____, which is (are) released by sediments on top of the subjecting plate.
- water
Pyroclastic flows that formed on Mont Pelee, Martinique, in 1902 were generated by ____.
- dome collapse
- hot water and magma overspilling the rim of the volcanic crater
What is a jokulhlaup?
- a glacial outburst flood triggered by a volcanic eruption
After residents of villages near Lake Nyos encountered a gaseous cloud in 1986, they ____.
- lost consciousness
- died of osphyxiation
Using ____ waves to predict volcanic eruptions is complex, since different waves can be produced by various volcanic processes.
- seismic
Nazko cone is a part of a chain of volcanoes orientated
- east-west
What is the distinctive characteristic of a tuya?
- flat top
More tha 7,000 pyroclastic flows, formed from ____, occurred on Mount Unseen, Japan, between 1991 and 1994.
- dome collapse
A decade ago, the Long Valley caldera was releasing 1,000 tons of carbon dioxide a day. Today, it is only releasing 300 tons a day. This suggests that _____.
- a volcanic eruption is less likely
Long, linear _____ eruptions composed of low-viscosity, low-volatile lava flows are typical in the country of Iceland.
- fissure
Most volcanic activity is not noticed by humans because _____.
- the majority of volcanic activity occurs at oceanic spreading centres.
Which of the following Canadian volcanoes are located in the Cascade Ridge?
- Mount Garibaldi, Mount Meager
Which of the following is a tertiary volcanic hazard?
- weather effects
As a result of the 1783 Lake fissures event in Iceland, ____.
- a famine killed about 10,000 people
- volcanic gases killed more than half of the country’s livestock (horses, sheep, and cattle).
- the growth of important agricultural plants was slowed
Imagine that the Kelut Volcano experienced an eruption last year. Recent heavy rainfalls have mixed with pyroclasts to produce a series of devastating lahars. How would a geoscientist classify the hazard associated with these lahars?
- secondary hazard
Ground deformation occurs when ____, potentially making it useful for predicting volcanic eruptions.
- magma moves upward beneath a volcano
A decrease in volcanic degassing does not always mean a decrease in volcanic activity. For example, decreases in degassing at the Galeras Volcano,Columbia, in 1993 was attributed to ____, leading to an eruption.
- sticky magma plugging the volcano
Nazko Cone is part of a chain of volcanoes oriented ____.
- east-west
The greatest lava eruption in the historic record is _____.
- the Lake fissure event in 1783
Lahars as a primary hazard occur ____, whereas lahars as a secondary hazard occur ___.
- during a volcanic eruption; months or years after an eruption.
One of the first signs of renewed volcanic activity of Mount St. Helens in March 1980 was ____.
- a series of small earthquakes
What did the inhabitants of Heimaey, Iceland, do to prevent lava flows from damaging the town’s harbour?
- sprayed seawater on theadvancing lava flows, causing them to rapidly cool and harden
Of the 62 people killed by the Mount St. Helen’s eruption, most of them died when ____.
- they ignored warnings to stay away from the volcano.
The release of carbon dioxide from Lake Nyos mirrors an earlier event at Lake Monoun in 1984. It is thought that this earlier event was probably due to ____.
- overturning of lac-waters layers during the rainy season
One example of a successful advance warning of a volcanic eruption is ____ .
- Mount Pinatubo in 1991
What is the name of the only hot spot in Canada?
- Anahim
Prior to the 2002 event, Nyiragongo had produced low viscosity lava flows during its 1977 eruption, which was caused by ____.
- low SiO2 content
The “mega-blister” that developed along the flank of Mount St. Helens in early April was the result of ____.
- an increase in magma volume within the volcano.
Carbon dioxide became trapped in Lake Nyos because the lake is _____.
- stratified into layers
Why did carbon dioxide build up to lethal levels in Lake Nyos?
- the gas, produced by volcanic outgassing, accumulated in the lower layers of the stratified lake until it reached critical levels.
haze
- suspended aerosols and particles that reduce visibility
jokulhlaup
- a glacial outburst flood
nuee ardente
- a turbulent “glowing cloud” of hot, fast moving volcanic ash, dust, and gas; also called a pyroclastic flow
pyroclastic flows
- high-temperature, fast-moving clouds of fine volcanic debris, steam, and other gases; also called anuee ardente.
volcanic belt
- a group of volcanoes located in a specific area
