Exam 6: Volcanic Eruptions: Plate Tectonics and Magmas

The three Vs of volcanology are __________________.

The most peaceful eruptions are _____________.

The most abundant dissolved gas in magmas is water.

Magma rising in a subduction zone tends to get more "contaminated" with high-silica minerals than does magma rising in a spreading ridge.

The presence of water ________ the melting point of rock.

No magmas contain dissolved gases.

The process of mineral formation in a cooling magma is called crystallization.

If the magma cools and solidifies below the surface,it crystallizes as volcanic rocks.

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

If the magma reaches the surface,it forms volcanic rocks,named for Vulcan,the Roman god of fire.

Basaltic magmas have low contents of SiO₂,low temperature,low viscosity,and allow easy escape of gases,producing peaceful eruptions.

Hawaiian volcanoes produce andesitic lava.

About 80 percent of the magma reaching the Earth's surface is basaltic,with only about 10 percent andesitic and 10 percent rhyolitic.

On 20 February 1943,a new volcano,a scoria cone,was born when an eruption rose up through a farm field near a village in Mexico.The volcano is ________________.

__________ eruptions are the most violent types of explosive eruptions.

A mantle hot spot has generated a long-lived plume beneath Yellowstone National Park,and the North American continent is drifting ___________ above it about 2 to 4 cm/yr.

When gas escapes quickly and violently from lava it may produce a frothy glass full of holes left by former gas bubbles;this porous material,known as pumice,contains so many holes it can float on water.

Because vulcanologists are aware of the potential hazards,no vulcanologist has ever been killed studying a volcano.

Silicon and oxygen link up to form the silicon-oxygen ______________.

The Volcanic Explosivity Index (VEI)ranges from 0 to 10.