GLY101 CH 7

During the 1990s, hundreds of trees were killed at Mammoth Mountain, California, by the diffuse emission of _________ gas.

CO2

Most of the people killed by the Mount St. Helens eruption of 1980 __________.

had gone around barriers meant to keep people out of 'harms' way

Dome collapse, overspilling crater rim, direct blast and eruption column collapse are all ways to generate __________.

pyroclastic flows

Violent causes of death from volcanic eruptions include _______________.

pyroclastic flows tsunami lahars poison gases

Most Icelandic eruptions are __________.

peaceful fissure eruptions

What was the origin of the gas that killed 1,700 people in Cameroon in 1996?

It leaked upward from basaltic magma underlying a lake

In 1883, __________ exploded and the resulting tsunami killed 36,000 people on Java and Sumatra.

Krakatau

Seafloor spreading generates __________ magma

basaltic

Why are low-latitudes the most dangerous latitudes to have a large volcanic eruption occur?

Ash and gases from low-latitude eruptions are spread around Earth to the greatest degree

Magma at 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

Pyroclastic flows cannot travel down all sides of a volcano simultaneously.

False

At Mt. St. Helens, about 60 people were killed in 1980, primarily by pyroclastic flows and effects related to lateral blast.

True

Pyroclastic flows can travel across bodies of water.

True

The most dangerous volcanoes tend to be in the same general plate-tectonic settings as the largest earthquakes in the world.

True

Volcanic eruptions can result in the formation of tsunamis.

True

What is the volcanic explosivity index (VEI) of a Yellowstone super-eruption?

VEI of 8

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

the subduction of the Juan de Fuca Plate beneath North America