EOSC 114 Final Exam Prep Objectives
Questions and Answers Detailed Answers
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what are the 3 regions of earthquakes in a subduction zone?
(Cascadia is a subduction zone)
(i) megathrust locked zone - brittle enough for the rupture to start,
possible hypocentre location
(ii) transition zone - too ductile for hypocentre, but fault could
rupture this deep once it has started
(iii) trench - location of plate boundary on the surface and the
tsunami starting location
describe characteristics of mafic magma (viscosity, silica
content, and temperature)
low viscosity, low silica, hot temperature
describe characteristics of felsic magma (viscosity, silica
content, and temperature)
high viscosity, high silica, cool temperature
viscosity and gas content are related to what?
explosivity
mafic explosions
low gas content and fluid, quiet, effusive eruptions, gas escapes
felsic explosions
high gas content and gooey, explosive, gas kept under increasing
pressure
icelandic eruption type
basalt, low volatile content, low viscosity, VEI (0-1), fissure
eruptions, low-volatile lava flows create wide volcanic plateaus of
nearly horizontal volcanic rock levels
hawaiian eruption type
, basalt, low volatile content, low viscosity, VEI (0-1), after initial
venting of gas, great quantities of basaltic lava spill out of fissures
and flow down mountain slopes
strombolian eruption type
basalt & andesite, medium volatile content, low and medium
viscosity, VEI (1-2), not strong enough to break cones, gas
pressure builds quickly beneath the crust, and eruptions occur as
distinct and separate bursts
vulcanian eruption type
basalt & andesite & rhyolite, medium-high volatile content,
medium-high viscosity, VEI (2-4). Eruptions alternate between
thick, highly viscous lava and masses of pyroclastic material
plinian eruption type
andesite & rhyolite, high volatile content, high viscosity, VEI (3-8),
incredible gas-powered vertical eruption columns, final phase in a
major eruptive sequence
volcanic rocks - basalt
dark colour, 45-55% SiO2 content, low viscosity magma, peaceful
eruption
volcanic rocks - andesite
medium colour, 55-65% SiO2 content
volcanic rocks - rhyolite
light colour, 65-75% SiO2 content, high viscosity magma,
explosive eruption
what do explosive eruptions require?
high silica content, cooler magma temps, and higher viscosity
define aa lava
a lava flow with a rough, blocky surface; slower-flowing, more
viscous
define pahoehoe lava
a lava flow with a smooth, ropy surface; highly liquid
cinder cones
mafic, explosive, layers of pyroclastic ejecta, frequent eruptions
Questions and Answers Detailed Answers
Latest Top Rated A+
what are the 3 regions of earthquakes in a subduction zone?
(Cascadia is a subduction zone)
(i) megathrust locked zone - brittle enough for the rupture to start,
possible hypocentre location
(ii) transition zone - too ductile for hypocentre, but fault could
rupture this deep once it has started
(iii) trench - location of plate boundary on the surface and the
tsunami starting location
describe characteristics of mafic magma (viscosity, silica
content, and temperature)
low viscosity, low silica, hot temperature
describe characteristics of felsic magma (viscosity, silica
content, and temperature)
high viscosity, high silica, cool temperature
viscosity and gas content are related to what?
explosivity
mafic explosions
low gas content and fluid, quiet, effusive eruptions, gas escapes
felsic explosions
high gas content and gooey, explosive, gas kept under increasing
pressure
icelandic eruption type
basalt, low volatile content, low viscosity, VEI (0-1), fissure
eruptions, low-volatile lava flows create wide volcanic plateaus of
nearly horizontal volcanic rock levels
hawaiian eruption type
, basalt, low volatile content, low viscosity, VEI (0-1), after initial
venting of gas, great quantities of basaltic lava spill out of fissures
and flow down mountain slopes
strombolian eruption type
basalt & andesite, medium volatile content, low and medium
viscosity, VEI (1-2), not strong enough to break cones, gas
pressure builds quickly beneath the crust, and eruptions occur as
distinct and separate bursts
vulcanian eruption type
basalt & andesite & rhyolite, medium-high volatile content,
medium-high viscosity, VEI (2-4). Eruptions alternate between
thick, highly viscous lava and masses of pyroclastic material
plinian eruption type
andesite & rhyolite, high volatile content, high viscosity, VEI (3-8),
incredible gas-powered vertical eruption columns, final phase in a
major eruptive sequence
volcanic rocks - basalt
dark colour, 45-55% SiO2 content, low viscosity magma, peaceful
eruption
volcanic rocks - andesite
medium colour, 55-65% SiO2 content
volcanic rocks - rhyolite
light colour, 65-75% SiO2 content, high viscosity magma,
explosive eruption
what do explosive eruptions require?
high silica content, cooler magma temps, and higher viscosity
define aa lava
a lava flow with a rough, blocky surface; slower-flowing, more
viscous
define pahoehoe lava
a lava flow with a smooth, ropy surface; highly liquid
cinder cones
mafic, explosive, layers of pyroclastic ejecta, frequent eruptions
