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