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