volcanoes
Over ________ of Earth's magma extruded through volcanism takes place at the oceanic spreading centers.
80%
Over ________ of volcanism is associated with the edges of tectonic plates.
90%
800-1,000 C, medium gray
andesitic
1,000-1,300 C, black to dark gray
basaltic
high viscosity, high volatiles, very large volume
calderas
pyroclastic debris is
chucks of magma and rocks blown into the air by gas in a volcanic eruption
why does the magma from some volcanoes flow smoothly and relatively peacefully, while the magma from other volcanoes blasts forth violently and deals death over wide areas?
differences in the chemical and mineral makeup of magmas, variations in the temperature, water and gas content, viscosity of magmas, and different geographic positions with respect to hot spots and edges of tectonic plates
low viscosity, low volatiles, very large volume
flood basalts
more vicious
increase SiO2 content, increase mineral crystal content
less vicious
increase temperature
this volcano erupted in 1883 in the Sunda Strait between Sumatra and Java, exploding with a loudness heard 3,000 miles away then collapsing into its magma chamber, making a caldera and setting off a tsunami that killed at least 36000 people
krakatoa
high viscosity, low volatiles, small volume
lava domes
lava flow
molten rock moving downslope
crater lake, oregon, fills the caldera of _______, which collapsed about 7600 years ago
mt mazama
lahars
muddy water-laden rush of material downslope
on 20 february 1943, a new volcano named ___________, a scoria cone, was born when an eruption rose up through a farm field near a village in mexico
paricutin
pyroclastic flow
rapid rush of gases and materials downslpoe
600-900 C, light colored
rhyolitic
low/medium viscosity, medium/ high volatiles, small volume
scoria cones
low viscosity, low volatiles, large volume
shield volcano
a mantle hotspot has generated a long live plume beneath yellowstone national park, and the north america continent is moving ________ above it about 2 to 4 cm/yr
southwestward
_______ are steep-sided, symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps
stratovolcano
medium/high viscosity, medium /high volatiles, large volume
stratovolcanoes
some of earths most beautiful moments are _________, including Mt Kilimanjaro in Tanzania, Mt Shasta in California, Mt Rainier in washington, and mt fuji in japan
stratovolcanoes
The volcanic explosivity index (VEI) measures size of volcanic eruptions on a scale of 0 to 8. between 1500 and 1980, one VEI 7 eruption occurred. this was _____________
tambora in 1815
what is the cause of volcanism at italys vesuvius, stromboli, vulcano and etna?
the subduction of Mediterranean seafloor beneath europe
a caldera collapse occurs
after the magma chamber is mostly empty
in magma, _____________ is the most abundant dissolved gas
water vapor (H2O)
a shield volcano has great _______________
width compared to its height
