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A high-pressure, fast-moving mixture of pyroclastic debris including fragments and gas typically ejected skyward from a volcanic vent is called A. a lahar |
B. an eruptive cloud or column. |
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A lahar is A. a glowing cloud of pyroclastic fragments and hot gas |
D. a volcanic mud flow that resembles fluid concrete |
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A moving, glowing cloud of hot gases and volcanic pieces A. was named with a Hawaiian term because it is so common there |
B. is called a pyroclastic flow or nuée ardente |
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Identify the FALSE statement. Lava of low viscosity A. can flow farther than intermediate- or high-viscosity lava |
C. is most often a "cool" temperature lava |
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Identify the FALSE statement. Plate tectonics theory explains why volcanic activity occurs where it does. For example A. active volcanoes in East Africa, such as Kilimanjaro, are the result of rifting (divergence) in continental crust |
C. the volcanoes of Iceland owe their existence to the mantle plume underlying the convergent plate boundary on which they sit |
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Identify the FALSE statement. Rhyolite lava A. has more silica than basalt lava does |
C. may be squeezed upward and out of the vent to create a lava fountain |
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Identify the FALSE statement. The eruption of Mt. Tambora, Indonesia, in 1815 A. is the only documented example of possible eruption-triggered coolness |
A. is the only documented example of possible eruption-triggered coolness |
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Identify the FALSE statement. Volcanic gases A. are more abundant in felsic lavas than mafic lavas |
B. are not harmful because most are less dense than air |
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In the 1980s, over 1700 people and thousands of heads of cattle from a village surrounding Lake Nyos, a volcanic lake in Cameroon, died unexpectedly after the lake overturned. They were not scalded, they were not poisoned, and the area did not smell bad. What volcanic gas killed the villagers and their cattle, and snuffed out their cooking fires? A. water vapor |
C. carbon dioxide |
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Lahars, composed of ash, debris, and water |
D. have often resulted in damage and death to humans and their property |
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Lava is A. always produced during any volcanic activity |
B. molten rock that cools and hardens on Earth’s surface |
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Mt. St. Helens erupted explosively in 1980. Geologists find evidence of many eruptions of Mt. St. Helens, dating back 37,000 years. The mountain is huge and is composed of layers of lava and pyroclastics. Which of the following is therefore most likely TRUE? A. When lava flows from Mt. St. Helens, it will be basalt |
C. Mt. St. Helens is a stratovolcano (or composite volcano). |
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Mt. Vesuvius erupted in a very violent explosion in 79 C.E. and buried the residents of Pompeii in ash. On the basis of this information, which of the following would you LEAST expect to find at Vesuvius? A. basaltic lava |
A. basaltic lava |
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The presence of pillow lava is evidence of what volcanic circumstance? A. a submarine volcano |
A. a submarine volcano |
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These volcanic products cover 70% of Earth’s surface. A. mid-ocean ridge volcanism |
A. mid-ocean ridge volcanism |
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This stratovolcano recently erupted in the United States. Although it warned of its impending eruption, it still killed people, partly because it first blew sideways and produced a monstrous landslide. The volcano is A. Surtsey |
B. Mt. St. Helens |
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Which of the following does NOT describe a structural feature of a volcano? A. vent |
B. vesicle |
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Which of the following explosive eruptions was enhanced by seawater flooding the magma chamber? A. Mt. St. Helens, Washington, 1980 |
D. Krakatau, Indonesia, 1883 |
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Which of the following is NOT a form of lava? A. a’a’ |
D. lapilli |
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Which of the following is NOT considered a warning sign of imminent eruption? A. earthquake activity |
C. a period of quiescence in the volcano’s activity |
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Which of the following volcanic areas is NOT part of the Ring of Fire? A. Iceland |
A. Iceland |
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