Most of the Earth's explosive volcanoes are located in a zone that encircles the Pacific Ocean called the Ring of Fire. The types of volcanoes that commonly form in this zone are called _____________ that form by the melting of asthenosphere and lithosphere rocks during _____________.
|A)||cinder cones, subduction|
|B)||shield volcanoes, subduction|
|E)||stratovolcanoes, formation of hot spots|
Melting of the mantle forms the most common type of magma that is extruded onto the Earth's surface because ______________.
|A)||this type of magma forms at high temperatures which allow it to rise to the surface before crystallizing completely to become solid rock|
|B)||this type of magma has low percentages of SiO2 so it has low viscosity which allows it to move more easily to the surface|
|C)||this type of magma is generally extruded in rift zones where there are fractures that provide avenues for flow|
|D)||all of the above|
|E)||none of the above|
Subduction zones are characterized by _______________.
|A)||andesitic to rhyolitic volcanic rocks|
|B)||steep-sided volcanoes composed of alternating pyroclastic debris and lava flows|
|C)||pyroclastic flows and calderas|
|D)||answers A, B, and C|
|E)||answers A and C|
At which location would you expect relatively peaceful volcanic eruptions?
|A)||Mt. Shasta in California|
|C)||Mt. Pinatubo in the Philippines|
|D)||Paricutin in Mexico|
|E)||Yellowstone in Wyoming|
Floods associated with melting of glaciers during a volcanic eruption are referred to as ____________.
Gases that are commonly emitted during volcanic eruptions include all of the following except _______________.
What was the gas that caused widespread death of people and animals near Lake Nyos in 1986?
During 1986 Lake Nyos eruption the most dangerous areas to be in were _________ because the gas was _________.
|A)||on top of hills, less dense than air|
|B)||on top of hills, flammable|
|E)||valleys, more dense than air|
The violent flank eruption of Mount St. Helens in 1980 was set off by _______________.
|A)||an earthquake that caused collapse of part of the mountain thus rapidly releasing pressure|
|B)||interaction of hot magma with cold water|
|D)||a fault that ripped the mountain apart|
|E)||none of the above|
Melting of thick caps of snow on volcanoes, such as Mount St. Helens, can generate which of the following hazards?
When magma is too viscous to flow it can form a sticky blob that blocks the conduit of a volcano and forms a steep-sided feature known as a _______________.
If you were in an airplane flying over a subduction zone what would you expect to observe on the continent adjacent to the zone?
|A)||A long, narrow sea within a rift zone.|
|B)||A plain of lava flows.|
|C)||A chain of steep-sided volcanoes subparallel to the subduction zone.|
|D)||A series of broad, shield-shaped volcanoes subparallel to the subduction zone.|
|E)||A single, large cinder cone.|
In 1902, the town of St. Pierre near Mt. Pelee was destroyed and its population of 28,000 killed because of _________________.
|A)||a gaseous flow of incandescent volcanic ash and dust|
|B)||a fast-moving basaltic lava flow that engulfed the town|
|C)||a rain of volcanic bombs|
|D)||an earthquake generated by the eruption|
|E)||none of these|
What causes a pyroclastic flow to move at high velocities?
|A)||Gravitational collapse of an eruption cloud.|
|B)||Energy from the eruption.|
|C)||Internal turbulence that keeps particles in the air.|
|D)||Release of gas from magma particles and heating of surrounding air creating a "popcorn" effect|
|E)||all of the above|
Why are pyroclastic flows one of the most dangerous types of hazard associated with volcanic eruptions?
|A)||They can form with little or no warning and move at extremely high velocities.|
|B)||They can cover large areas with a dense cloud of ash and dust that can asphyxiate an entire city.|
|C)||The temperature of the cloud can be several hundred degrees Centigrade causing fires.|
|D)||answers A and B only|
|E)||answers A, B, and C|
Lahars created on stratovolcanoes have high destructive energy because _______________.
|A)||they move at velocities of 200-300 miles per hour|
|B)||they flow on top of a cushion of hot gases and heated air|
|C)||they are dense mass of water and rock that flows down steep slopes over thousands of feet of elevation|
|D)||they gain energy as powerful eruptions eject material out of the vent|
|E)||they form when an entire volcano collapses|
Which continental hot spot in the United States has posed the greatest threat in historic times?
|B)||Long Valley caldera|
Lahars can form by all of the following except ________________.
|A)||melting of a snow cap on a volcano|
|B)||flow of lava into the ocean|
|C)||flow of pyroclastic material into a river|
|D)||heavy rainfall during eruption of pyroclastic material|
|E)||collapse of a crater lake or dam|
A pyroclastic flow can best be described as _________________.
|A)||a flow of gas and hot ash|
|B)||a flow of hot gas|
|C)||a flow of mud and pyroclastic material|
|D)||a flow of hot lava|
|E)||a rain of volcanic fragments|
Which of the following hazards to humans are related to volcanic eruptions?
|A)||Burial by volcanic-generated mudflows.|
|B)||Asphyxiation from volcanic gases.|
|D)||Being struck by pyroclastic debris.|
|E)||all of the above|
The two most frequent causes of death from volcanic eruptions are
|A)||lava flows and suffocation from volcanic gases.|
|B)||famine and jokulhaups.|
|C)||pyroclastic flows and tsunami.|
|D)||pyroclastic fall (bombs) and lahars.|
|E)||debris avalanches and earthquakes.|