GEOL 1170 Quiz 6

On 8 May 1902, a massive eruption of ________ killed 30,000 people in the town of St. Pierre.

Mont Pelée, Martinique,

A genuine success story of advance warning before a large eruption occurred in the Philippines in 1991 before the climactic eruption of ________.

Mt. Pinatubo

When magma crystallizes slowly, _____ are formed.

intrusive (plutonic) igneous rocks

Which type of volcano results from high viscosity, low volatiles, and small volume? (sorry - on an earlier version of this question there was a typo)

lava dome

What is a stratovolcano?

A steep-sided volcano composed of alternating layers of lava and pyroclastics

Which of the following plate boundaries hosts lots of volcanoes that erupt mainly basalt?

Divergent boundary

Mt. St. Helens killed a geologist studying the volcano because ____________.

a landslide produced a lateral blast of volcaniclastic debris that no one anticipated

Slow flowing, more viscous basaltic lava commonly has a rough, blocky texture called ________.

aa

Magma at oceanic spreading centers is low-temperature, high-viscosity, and granitic, with easy escape of gases, providing all the factors that promote the peaceful eruption of magma.

false

Several geologic phenomena are being studied as signs of an impending volcanic eruption. These include seismic waves, ________, and the release of gases.

ground deformation

Which type of volcanic rock below has the highest silica (SiO2) content?

rhyolite

Active volcanoes today in Oregon and Washington, including Mt. St. Helens, result from ________.

the subduction of the Juan de fuca plate beneath North America

The fossils seen at Ashfall, Nebraska, perished as result of an eruption of Yellowstone some 1500km (931mi) away.

true

The primary reason magma forms at subduction zones is that the subducting plate carries a cover of sediments, water, and hydrated minerals down with it, which lowers the temperature required for the adjacent overlying mantle lithospheric rock to melt.

true

A shield volcano has a greater ________.

width compared to its height