Ch. 7 - HW (volcano case histories)

The energy behind the 1902 pyroclastic flow that destroyed St. Pierre came from _________________.

-the blast of the volcano -gas escaping from pieces of airborne pyroclastic material, creating a "popcorn" effect -gravity *All of these choices are correct.

Airline traffic was disrupted for 6 months during the 2010 eruption of Eyajafajallajokull in southern Iceland.

false

On 8 May 1902, a massive eruption of __________ killed 30,000 people in the town of St. Pierre.

Mont Pelée, Martinique,

Nuee ardente (French for glowing cloud) is another term used to describe a lava flow.

false

The vulcanian eruption of Eyajafjallajokull in southern Iceland in 2010 resulted from __________.

glacial meltwater pouring into the magma chamber

Lassen Peak is an unusually large, SiO2-rich, lava dome.

true

Pyroclastic flows can travel across bodies of water.

true

The eruption of Nevado del Ruiz in Columbia in 1985 dropped hot pyroclastic debris onto glaciers, resulting in lahars.

true

The fossils seen at Ashfall, Nebraska, perished as result of an eruption of Yellowstone some 1500km (931mi) away.

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

Violent causes of death from volcanic eruptions include _______________.

-lahars -tsunami -poison gases -pyroclastic flows *All of these choices are correct.

In 1985, __________ produced a minor eruption that melted part of a glacier near its summit, sending a lahar down its slopes and killing at least 22,000 people.

Nevado Del Ruiz, Colombia,

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

Most Icelandic eruptions are __________.

peaceful fissure eruptions

The two most active Cascade Range volcanoes over the past 4,000 years are _______________.

Mt. St. Helens and Mt. Shasta

Volcanic eruptions with which of the following VEIs happen the most often?

VEI of 3

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

the subduction of the Juan de Fuca Plate beneath North America

Mt. Rainier, Washington, is number one on the danger list of many U.S. volcanologists because of its __________.

All of these choices are correct.

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.

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

CO2

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

During the summer of 1783, the greatest lava eruption of historic times poured forth at _________, accompanied by the release of an enormous volume of gases that enshrouded much of northern Europe in a "dry fog" or blue haze rich in SO 2 (one of the visible components of today's urban smog).

Laki, Iceland

In the United States, there was great concern in the early 1980s when earthquakes were frequent, including harmonic tremor, and four magnitude 6 earthquakes caused damage near __________.

Long Valley Caldera in California

A genuine success story of advance warning before a large eruption occurred in the Philippines in 1991 before the climactic eruption of _________________.

Mt. Pinatubo

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

VEI of 8

Viscous magmas are stored as a mostly solid, crystalline mush. It can be activated by which of the following?

an injection of new, hot magma and fracturing by fault movements that connect to isolated magma bodies and reduce the pressure

Seafloor spreading generates __________ magma.

basaltic

In August 1986, a gigantic volume of __________ belched forth from Lake Nyos in Cameroon and swept down the adjacent valleys asphyxiating 1,700 people.

carbon dioxide

The Toba eruption 74,000 years ago may have __________.

caused a great reduction in the worldwide human population

All volcanic activity in a failed rift ceases once the rifting fails.

false

At Lake Nyos in 1986, a gas cloud wiped out all nearby plant and animal life.

false

Several geologic phenomena are being studied as signs of an impending volcanic eruption. These include seismic waves, ______________, and the release of gases.

ground deformation

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

The Mt. Pinatubo endangered people, animals, and property when its 1991 eruption resulted in __________.

lahars and pyroclastic flows

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

pyroclastic flows

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

true

In Icelandic-type eruptions, low-viscosity, low-volatile content lava erupts peacefully.

true

People living below Mt. Shasta should be concerned because of lahars and the tendency they have to flow down valleys.

true

The plate-tectonic process responsible for volcanoes in the Pacific Northwest region of North America is identical to the cause of the region's great earthquakes—subduction of the Juan de Fuca Plate.

true

The radiocarbon process of documenting major eruption dates for volcanoes in the past 50,000 years or so is the same as that used to work out dates of major prehistoric earthquakes.

true