Which magma is most likely to quench (congeal) to a natural glass?
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Magma
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________ is the name given to molten rock below the Earth's surface.
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quiet outpourings of fluid lavas
answer
Which of the following characterizes a typical eruption of Kilauea Volcano in Hawaii?
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Composite
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What type of volcano is Mount St. Helens?
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A massive landslide
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Which of these most directly triggered the main eruption?
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Moving magma had over-steepened the mountain slopes.
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There had been many earthquakes in the area prior to this eruption. Why did this last earthquake trigger a massive landslide?
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If the northern slopes had been less steep initially (same height), the eruption would likely have happened later.
If the volcano had been significantly shorter initially (same steepness), the eruption would likely have happened sooner.
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If previous eruptions had left Mount St. Helens with a different shape, what differences might have influenced the timing of the eruption?
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2.8 cubic kilometers of rock
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How much material was removed from the volcano?
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Water
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________ is a major dissolved volatile constituent in both magmas and volcanic gases.
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none of the above
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Why would a plume of solid silicate rock rising slowly from deep in the mantle begin melting as it neared the base of the lithosphere?
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Intrusion of basaltic magma causes deep crustal rocks to melt, producing andesitic or rhyolitic magmas.
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Pockets of magmas can be formed by the melting of deep continental crust heated by the intrusion of other magmas. Which of the following correctly describes this process?
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submarine; basaltic lava flows
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Which kind of volcanism is typical of mid-oceanic ridge systems?
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the circum-Pacific area
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Which region has the greatest concentration of currently active volcanoes?
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they lie on a spreading center where two plates are moving apart
answer
The Icelandic volcanoes are related to plate tectonics because ________.
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related to plate subduction
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Which one of the following best describes volcanism in the Cascade Range, northwestern United States?
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the volcanoes of Hawaii and Quaternary activity in Yellowstone National Park
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Which of the following is associated with deep mantle hot spots?
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convergent plate boundary volcanism
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What type of volcanism is associated with the zone of active volcanoes called the Ring of Fire?
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composite
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Which kind of volcano is closely associated with convergent plate boundaries and subduction zones?
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Intraplate volcanism occurs both on continental and oceanic landmasses.
Intraplate volcanism usually erupts basaltic lava.
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Which of these are true about intraplate volcanism?
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True
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The viscosities of magmas increase with increasing percentages of silica.
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Magmas are mainly liquid and contain dissolved fluids such as water; most are less dense than the adjacent solid rock.
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Why do magmas rise toward Earth's surface?
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False
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Most basaltic magmas are believed to form by partial melting of granite in the lower crust and upper mantle.
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True
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Dissolved gases may comprise up to a few percent by weight of a magma.
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False
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Basaltic lavas are generally hotter and more viscous than andesite lavas.
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because potential eruptions are highly explosive and less predictable
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Why does a volcano fed by highly viscous magma pose the greatest threat to life and property?
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volcanism
answer
What geologic process is related to caldera formation?
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Calderas form when the summit of a volcano collapses.
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How do calderas form?
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Oregon
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Where is Crater Lake?
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The eruption was so large that the magma chamber under Crater Lake partially emptied, causing the volcano to become unstable and collapse.
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In addition to rock deposits, what evidence do we have that the eruption that preceded the formation of Crater Lake was very large?
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The volcano is still active, and a new volcanic peak has formed.
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Why does Crater Lake have an island in it?
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They are old dikes radiating from the main neck of the volcano.
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How did the ridges around Shiprock form?
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The rocks in Shiprock formed when magma solidified in the neck of an old volcano.
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They are old dikes radiating from the main neck of the volcano.
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All of the lava and pyroclastic material and some of the volcanic neck were eroded.
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How did erosion affect Shiprock?
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An igneous rock associated with continental volcanic activity
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The composition of the rocks that make up Shiprock would most likely be similar to which of the following rocks?
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crater
answer
A relatively small, summit depression on a volcano, marking a former eruptive vent, is a(n) ________.
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A nueé ardente
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________ destroyed the city of St. Pierre, Martinique in 1902.
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Sulfur dioxide and other erupted gases formed aerosols in the stratosphere.
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The 1991 Pinatubo eruption in the Philippines caused brilliantly colored sunrises and sunsets to be seen for the next few years. What caused this phenomenon?
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pyroclastic flows
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Which volcanic hazard is considered to be the most destructive?
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They erupt silica-rich lavas that cool to andesite or rhyolite.
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Which of the following statements is true of composite volcanoes?
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ground deformation on the top or side of a volcano
changes in earthquake patterns near the volcano
changes in gas composition
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Which of the following indicates the possibility of an imminent eruption? Choose all that apply.
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They form over short periods of time, often after a single eruption event.
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Which of the following statements describes a cinder cone volcano?
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shield
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A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows.
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pahoehoe flow
answer
Which of the following is a product of a shield volcanic eruption?
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False
answer
In general, cinder cones are much larger than shield volcanoes.
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volcanic gases
answer
What type of material is emitted through a fumarole?
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crater
answer
A ________ is formed on the volcano summit by explosive eruptions and is composed of accumulated volcanic debris.
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caldera
answer
Depletion of the upper part of a magma chamber during a volcanic eruption can result in gravitational collapse of the volcanic summit to form a ________.
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vent
parasitic cone
answer
A ________ is an opening where volcanic materials erupt at the Earth's surface, and can form on the flanks of a larger volcano in the case of a ________.
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conduit
answer
The pipelike feature through which magma travels upward from an underground magma chamber is called a ________.
question
magma chamber
answer
A ________ results when magma collects or ponds due to its density being higher than that of overlaying materials.
Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface?
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as erupted magma blobs that partly congeal before falling to the ground
answer
Volcanic bombs originate ________.
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Water and carbon dioxide
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________ are usually the most abundant gases emitted during basaltic volcanism.
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aa
answer
Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble?
question
Tambora, Indonesia, 1815
answer
Which was the most powerful, explosive volcanic eruption of historic time?
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block lava
answer
Which of the following is typically associated with rhyolitic magma?
question
True
answer
Ash and lapilli are different sized pyroclastic particles.
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the picture with basalt on the left
answer
pictures brah
question
Flood basalts are layers of solidified, low viscosity lava that flowed out across the Earth's surface.
The basalt layers likely indicate repeated eruptions of multiple lava flows that decrease in age as you move up the layers to the top of the basalt plateau.
answer
Select the correct statements below regarding these igneous rock types and the Columbia River Basalt Plateau.
question
A large mantle plume begins to rise from deep within the Earth.
The mantle plume head undergoes decompression melting, generating a large volume of magma.
Magma finds its way to the surface via fissures, causing an initial massive extrusion of flood basalts.
The eruptions begin to wane as the plume head is emptied.
answer
Use your knowledge about how basalt provinces form to place the following events in sequence from oldest to youngest.
question
Pyroclastic Ash Flow
Aa Lava Flow
Pahoehoe Lava Flow
Bombs
answer
more pictures brah
question
an explosive stratovolcano
answer
Mount St. Helens is ________.
question
volcanism caused by convergent oceanic-oceanic boundaries
volcanism caused by convergent oceanic-continental boundaries
answer
What type of volcanism characterizes the ring of fire?
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divergent oceanic-oceanic
answer
What type of boundary is present along the eastern boundary of the North American plate?
question
oceanic hot spot
answer
At what tectonic setting is Hawaii located?
question
decompression melting
answer
What drives melting at divergent boundaries?
question
transform boundary
answer
Which of the following tectonic settings does NOT produce volcanism?
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