Chapter 6 Quiz

The volcanic explosivity index (VEI) measures size of volcanic eruptions on a sclae of 0 to 8. Between 1500 and 1980, one VEI 7 eruption occured. This was ____.

Tambora in 1815

Although there are 92 naturally occurring elements, a mere eight make up more than 9 percent of Earth's crust.

True

At oceanic spreading centers, magmas are rhyolitic in composition.

False

Eruptions in Hawaii are always peaceful.

False

Over ____ of Earth's magma extruded through volcanism takes place at the oceanic spreading centers.

80%

The formation of a giant continental caldera include all but which of the following?

Basaltic eruptions begin forming circular fractures surrounding the bulge.

Crater Lake, Oregon, fills the caldera of ____ which collapsed about 7,6000 years ago.

Mt. Mazama

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

The number of active "hot spot" on Earth over the last 10 million years active is ____.

more than 100

If basaltic lava reaches the sea or a lake, it cools rapidly into ____ lava.

pillow

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

tetrahedron

A shield volcano has a great ____.

width compared to its height