Quiz 6
This volcano erupted in 1883 in the Suna Strait between Sumatra and Java exploding with a loudness heard 3000 miles away then collapsing into its magma chamber making a caldera and setting off tsunami that killed at least 36000 people
Krakatua
the volcanic explosivity index VEI measures size of volcanic eruptions on scale of 0 to 8 between 1500 and 1981 one VEI 7 eruptions occurred this was
Tambora in 1815
Transform faults have lots of associated volcanism because the strike slip motion keep a lid on the hot asthenosphere below allowing it to melt
false
no magmas contain dissolved gases
false
the higher the viscosity of the magma, the more fluid is its behavior
false
the most peaceful eruptions are
icelandic type eruptions
the viscosity of magma is lowered by
increasing temperature, decreasing crystal content, decreasing SiO2 content
____ are steep sided symmetical volcanic peaks built of alternating layers of pyroclastic debris capped by high viscosity andestic to rhyolitic lava flows that solidity to form protective caps
stratovolcanoes
although there are 92 naturally occurring elements a mere eight make up more than 98 percent of the Earth's crust
true
the most famous of all volcanoes probably is vesuvius and and the most famous of its eruptions are those of 79 CE which buried the cities of
pompeii and herculaneum
Crater Lake, Oregan fills the caldera of ____ which collapsed about 7600 years ago
Mt Mazama
____ eruptions are the most violent types of explosive eruptions
Plinian type
the formation of a giant continental caldera includes all but which of the following
basaltic (P) eruption begin from circular fractures surrounding the bulge. (Correct: rising magma forms a low density cap rich in SiO2 and gases bulging the ground surface upward, magma pours out in high volume pyroclastic flows causing the ground surface to sink into a caldera, removal of magma decreases the pressure on the magma below the caldera causing new magma to bulge up the caldera floor
Mineral growth in magmas at the surface with temperature around 1000 to 12000C occurs in the following way
iron and magnesium will link up with aluminum and the silicon oxygen tetrahedron as a magma temperature decreases to sequentially form four distinct and discontinuous families of minerals, calcium will combine with aluminum and the silicion oxygen tetragedron to begin forming the plagiociase feldspar family a continuous and gradational series of minerals
Rock may melt by
lowering the pressure on it, raising its temperature, increasing its water content
silicon and oxygen link up to form the silicon oxygen
tetrahedron
the typical trend in the rising plume of subduction zone magma is to increase
the percentage of SiO2, the viscosity, the explosive potential of the magma by holding in the gases more tightly
what is the cause of volcanism at italy's vesuvius, stromboli, vulcano, and etna
the subduction of Mediterranean sea floor beneath Europe
spreading centers are an ideal location for volcanism because
they sit above the high temperature asthenosphere, the asthenosphere rock has low percentages of SiO2, the oceanic plates pull apart causing hot asthenosphere rock to rise and undergo decompression melting to form magma that continues to rise
beneath continents risking basaltic magmas are contaminated by sediments and continental crust rocks altering magma compositions the resultant andesitic to rhyolitic magmas have high content of SiO2 relatively low temperature and high viscosity which make it difficult for gases to escape cuasing explosive eruptions
true
