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107 Cards in this Set
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Define volcano |
opening of the Earth’s surface where magma has poured or blown forth, typically creating hills or mountains Form where magma/gas leak out of Earth’s crust/mantle |
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Define magma |
molten rock material that solidifies on the Earth’s surface as volcanic rock and at depth as plutonic rock Created by melting pre-existing rock below the Earth’s surface Reach surface through fractures/extrudes as lava or explodes as pyroclastic material |
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Define lava |
magma that flows to the Earth’s surface |
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Describe the 4 stages of the volcanic system in chronological order. include where it is happening |
Source region: where the mantle is melting - Where the mantle (peridotite) melts into magma of various types - Becomes less dense - Pockets of melting Transport region: magma channels - Where the magma is trying to get through the crust - Magma moves along earth’s crust forming dikes and sills Storage region - Little bits of melt rising, cooling, and ponding in large chambersIn the crust Eruption: Volcanoes on the surface |
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Define dike |
vertical intrusion of magma |
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Define sill |
horizontal intrusion of magma |
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Give the approximate densities of magma, crust, mantle, and water |
Magma: 2.5-3.3 g/cm^2 water is 1 g/cm^3 Crust: 2.7-3.3 g/cm^3 Mantle: 3.3-5.7 g/cm^3 |
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Define viscosity |
resistance to flow |
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What factors affect magma viscosity |
temperature, gas content, and crystal content |
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How does viscosity affect eruptions |
Controls the flow and eruption style |
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Describe the physical properties of felsic igneous rock. give one example |
high silica content (65-75%) Light color Rich in K, Na, Al, Si High viscosity (sticky) Eg. granite, rhyolite |
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Describe the physical properties of mafic igneous rock. give an exampe |
Dark color Rich in Mg, Fe Low viscosity (runny) Eg. Basalt, Gabbro |
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Name characteristics of hot magma. which magma is hot |
low viscosity, low silica Mafic |
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Name the characteristics of cool magma. which magma is cool |
high viscosity, high silica Felsic |
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Which magma has more gas content? Name 2 gases that are dissolved in them |
felsic has more dissolved volatiles. Gases dissolved: H2O, CO2, SO2, CI |
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What type of eruption does mafic magma produce? |
low gas content+low viscosity=effusive eruptions (safe) |
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What type of eruption does felsic magma produce? |
high gas content+high viscosity=explosive eruptions the gas kept under pressure makes it dangerous explosion |
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Name the characteristics of basalt rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style |
Black to dark grey, 80%, 45-55%, 1000-1300 C, Low, ~0.1-1wt, Easy, Peaceful |
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Name the characteristics of andesite rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style |
Medium-dark grey, 10%, 55-65%, 800-1000 C, medium, ~2-3 wt%, More difficult, More explosive |
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Name the characteristics of rhyolite rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style |
Light colored, 10%, 65-75%, 600-900 C, high, ~4-6wt%, difficult, explosive |
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Define pahoehoe lava |
a basalt lava flow with a smooth, ropy surface |
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Define Aa lava |
a basalt lava flow with a rough blocky surface |
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What 2 main places do volcanoes occur on |
Plate boundaries, Hotspots |
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What type of lava would one find at each type of plate boundary |
divergent- mafic, convegent-felsic |
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What is an arc volcano |
chain of volcanoes formed above a subducting plate, positioned in an arc plate |
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Descripe the eruptions at divergent boundaries |
Spreading centres allow peaceful eruption of magma The most magma is erupted in this way |
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Describe the eruptions at convergent boundaries |
Commonly explode violently Magma temperature decrease, SiO2/water/viscosity increase |
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Define hotspot |
places inside the mantle where rock melt to generate magma |
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Where do hotspots occur? |
Fracture zones Volcanic calderas (rhyolite rocks) Under continental crust - Ie Yellowstone Under oceanic crust - Ie. Hawaii |
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what are the 4 main types of volcanoes |
Cinder cones: mafic, explosive Shield volcanoes: mafic, non-explosive Stratovolcanoes: intermediate, felsic, mixed Calderas: felsic, explosive |
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Define the angle of repose |
the steepest angle at which a sloping surgace formed of a particular loose material is stable |
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What is the frequency of cinder cones |
frequent |
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what is the frequency of shield volcaneos |
frequent/permanent |
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What is the frequency of stratovolcanoes |
frequent |
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What is the frequency of calderas |
rare |
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Define effusive eruptions. what types of activity are associated with these types of lava flows and which types of magma do they occur for |
outpouring of molten magma from the vent → lavas Passive eruptions of magma - Lava flows (mafic-intermediate) - Lava domes (felsic-intermediate) - Gravitational collapse of lava flows/domes - Pyroclastic flows |
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Define explosive eruptions. |
gas driven violent eruptions → pyroclastic deposits Buoyant eruption column of ash Pyroclastic airfall Pyroclastic flows (column collapse) Blocks and bombs proximal to vent |
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Define pyroclastic fall |
Eruption columns: 10’s of km Widespread distribution of ash in the downwind direction Ash blankets topography |
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Define pyroclastic flow |
Gas-pyroclast mixtures Gravity-driven flows Flow down slope, channelled in valleys velocity=40 to >400 km/h temperatures=100-600 C |
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What is the "key" to explosive volcanism |
high gas and high viscosity |
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What are the steps to an eruption from the bottom of the volcano to the top? |
In the magma reservoir, there is magma with dissolved volatiles Reaches the saturation surface Exsolution surface → bubble nucleation Bubble growth, bubble rise up the volcano within the magma OutgassingFragmentation Release as volcanic plume composed of pumice and ash |
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Name the 5 types of eruption |
hawaiian, strombolian, vulcanian, plinian. phreatmagmatic |
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Define the volcano explosivtiy index |
describes the size of an explosive volcanic eruption, scale 0-8 |
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What are the characteristics of a hawaiian eruption |
Low viscosity basaltic magma Low explosivity (effusive) - Lava flows - Fire fountaining |
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What are the characteristics of a strombolian eruption |
basaltic/andesitic magma Mildly explosive Bomb, lavas |
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What are the characteristics of a vulcanian eruption |
Viscous andesitic/rhyolitic magma Very explosive Sustained explosions of ash |
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What are the characteristics of plinian eruptions |
andesitic/rhyolitic ash Violently explosive Sustained column of ash Pyroclastic flows |
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What are the characteristics of phreatomagmatic eruptions |
Contact between water/magma Water flashes to steam Violently explosive Surtseyan and phreatoplinian |
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What characteristics are key in deciding the VEI of a volcano |
Volume of ash produced Height of eruption cloud above vent Duration of the eruption*** Total erupted volume explosively |
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For every increase in interval on the VEI, what is the increase in size of eruption |
10 times larger |
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What are the rough VEIs for hawaiian, vulcanian, plinian, and ultra plinian volcanoes |
Hawaiian: VEI 1 Vulcanian: 3 Plinian: 5 Ultra Plinian: 6 |
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True or false, some large eruptions can cause global cooling |
true |
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true or false, as the VEI increase, the return period of another eruption of the same scale also increases |
true |
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What is a hazard |
any event that could cause human or economic harm |
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What is a risk |
the probability that a hazardous event may occur |
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Name 5 volcanic hazards |
lava flows, pyroclastic ash fall, pyroclastic flows, lahars, sector collapse/debris avalanche, volcanic gases |
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Define a lava flow |
Slow, Usually not dangerous, Easy to predict the flow path, Usually mafic and low viscosity usually not a hazard to people but a hazard to buildings |
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Define a fire fountain |
If basaltic lava is gas rich, small explosive eruptions from fire fountains As particular liquid drops fall back on the ground, they may come together to form a lava flow |
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Define a spindle bomb |
a football shpaed clot of magma that is chucked out of a volcano --> associated with low explosivity |
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Define pyroclastic fall |
aka ash fall hot ash and gas ejected from the volcano can casue total darkness, roof collapse (most dangerous, and asphyxiation |
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Define pyroclastic flows |
avalanche of pyroclastic material, air, and gas driven by gravity can travel 40-400km/h |
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what are some triggers of pyroclastic flow |
collapse of a volcanic column (most common) explosive collapse of lava domes |
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what are some ways to reduce the threat from pyroclastic flow |
prevent construction/evacuate around the base of the volcano aovid building where previous pyroclastic flows have occured |
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Define a lahar |
volcanic mud/debris flow flows of water and loose volcanic debris prevalent at snow and ice clad volcanoes can trave far and can occur without eruption |
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define a sector collapse/debris avalanche |
a volcanic landslide can occur when a volcanic edifice is weakened scalloped scar remains |
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Describe volcanic gases |
highly acidic and toxic kills plants and animals composed of water, carbon dioxide, HCl, SO2, and HF |
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Define fumarole |
an opening in the volcano that may emit volcanic gases |
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What are the 3 steps for volcano prediction |
1. geology and mapping 2. monitoring seismology and earthquakes, ground deformation, and gas emission, thermal imaging, lahar flow detction, and satellite observation 3. prediction and hazard analysis |
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Describe the eruption warning levels |
GREEN (normal): volcano is in typical background, non-eruptive state or after a change from a higher level, volcanic activity has ceased and volcano has returned to non eruptive background state YELLOW (advisory): volcano is exhibiting signs of elevated unrest above known background level OR after a change from a higher level, volcanic activity has decreased significantly but continues to be monitored for possible renewed increase ORANGE (watch): volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain OR eruption is underway but poses limited hazards RED (warning): hazardous eruption is underway, imminent, or suspected |
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What does the interferometric synthetic aperture radar (InSAR) do? |
measurements by satellites to detect changes in elevation |
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What does the tiltmeter do |
measures changes in angle of slope |
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What does the GPS do in volcano monitoring |
measures changes in position |
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What do spectrometers do |
measure carbon dioxide and sulfur oxide levels in gas from a distnace |
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What are the 2 types of spectrometer and what are their differences |
FTIR (fourier transform infrared spectromter): used to measure dissolved volatiles in magma COSPEC (correlation spectrometer): used to measure sulfur oxide in a volcanic plume |
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How can you tell a rock if a rock is intrusive or extrusive |
the more crystal, the more intrusive it is |
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At what type of convergence is there no volcano? |
continental continental |
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What is the most common volcano at subduction zones |
stratovolcanoes |
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What si the most common volcanoes at hotspots |
caldera and shield |
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Where do cindercones appear |
anywher on the surface where there is basaltic magma and a little bit of gas leaks from it |
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What is the difference between a flow and a slide |
a flow: everything is mixed up a slide: everything is almost moving in a giant in tact-block |
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what are some other terms for landslide |
mass movement, mass wasting, slide |
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What are 3 factors that govern human and economic impact of landslides |
population density, cost of infrastructure, population preparedness |
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what is the rough annual human impact of landslides in vancouver, us, and japan |
Canada-3, us-30, Japan-200 |
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True or false: most fatalities are associated with the landslide trigger and not the landslide itself |
true |
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Why does BC get so many landslides? |
there are mountains everywhere |
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What is the return period of large landslides in BC |
25-70 years |
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Name 3 large landslides in BC |
In order of date: rubble creek (garibaldi), frank slide, britannia beach 1915, britannia beach 1923, hope slide, mt meager |
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How are landslides classified?` |
type of material, type of movement, rate of movement only material and type of movement used for name |
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Name the 4 types of material a landslide can be composed of |
rock, soil/earth, mud, debris |
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Name the 4 types of motion |
falls, slides, flows, complex movements |
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What is the difference between a rotational and translational slide |
rotational: curved bowl shaped failure surface translational: flat/planar failure surface |
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What will the name of the motion be if the movement of a landslide is slow or slower |
creep, soil flow, or earht flow |
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Where and why do falls occur |
falls are very fast and they occur on steep slopes where the material detaches because of weakness. the fall then occurs due to gravity |
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Describe the characteristics of a rotational slide |
intermediate speed, usually weak material, rotation of material on a curved plane, often characterize by a curved scarp above the slide |
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Describe the characteristics of a translational slide |
slow to fast, usually strong material moving on planes of weakness, cohesive motion on a flat surface |
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describe the characteristics of flows |
very slow to very fast, soil mud or wet debris, water usually an important factor, fluid or plastic flow material |
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Which forces are involved in the stability of slopes |
gravity and shear force (motion from side to side, component of force parallel to the slope), friction, cohesion (how the materials hold together) |
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What is shear strength |
slopes ability to resist shearing motion |
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When does failure occur? |
when shear strength is less than shear stress |
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How do you calculate factor of safety (Fs) |
Fs=shear strength/shear stress Fs less than one =failure |
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What is the Factor of safety at the angle of repose? |
exactly 1 |
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What are some external causes of landslides? |
slope angle, undercutting overloading, vegetation (roots can bind loose material, removing them can make slopes unstable), climate: high temp and rainfall (weathered rocks, looser soil) |
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What are some internal causes of slides? |
water content (can help or hinder cohesion but also weathers materials), weak material (eg. volcanic rock or quick clay), bad geological structures |
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Define a trigger. list 5 for landslides |
A force or event that disrupts the equilibrium of a slope and intiates mass movement eg. earthquakes, snow melt, heavy rainfall, rain or snow, loud noises, vehicles, eruptions, excavation, skiing, jumping up and down |
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Describe the oso landslide |
march 22 2014, 45 days of heavy rain (cause), collapse of layers of glacial sediment (cause), trigger unknown but not earthquake, fast moving wall of mud, caused tsunami, 43 fatalities |
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what are the 3 paths to mitigate landslides |
avoidance, prevention, protection |
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what is the main problem with avoiding landslides |
too expensive |