In 1980, ____ was the first Cascade Range volcano to erupt since Mt. Lassen, California, in 1915-16
Mt. St. Helens
Volcanic bombs originate _____
as erupted magma blobs that partly congeal before falling to the ground
Which natural phenomenon occurs for many years after major explosive volcanic eruptions such as Tambora and Pinatubo?
brilliantly colored sunrises and sunsets
What fate befell the ʹLost City of Atlantisʹ mentioned in Platoʹs writings?
it disappeared as part of caldera collapse following a major, explosive, volcanic eruption
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?
sulfur dioxide and other erupted gases formed aerosols in the stratosphere
Which of the following is associated with deep mantle hot spots?
the volcanoes of Hawaii and Quaternary activity in Yellowstone National Park
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?
temperatures remain high as lowered pressures decrease melting temperatures
Which of the following best describes seamounts and islands of the deep ocean basins?
piles of basaltic lava flows built up from the ocean floor by multiple, summit and flank
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?
intrusion of basaltic magma causes deep crustal rocks to melt, producing andesitic or rhyolitic magmas
Which of the following phenomena accompanied the year without a summer (1816) in parts of North America and northern Europe?
snow falls and frosts in New England during July and August
________ are usually the most abundant gases emitted during basaltic volcanism.
Water and carbon dioxide
Which statement about the May, 1980, eruption of Mount St. Helens is false?
during the eruptive period, the mountain peak was substantially built up by new lava flows
and pyroclastic debris
________ tend to increase the explosive potential of a magma body beneath a volcano.
High viscosity and dissolved gas
Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble?
Which one of the following statements concerning volcanic blocks and bombs is true?
bombs are ejected as magma lumps; blocks are ejected as solid fragments
Which one of the following statements concerning cinder cones is false?
the cinders and other pyroclastic particles are consolidated into welded tuff
Which kind of eruptive activity is most likely to be highly explosive?
eruptions of big, continental margin, composite cones or stratovolcanoes
Which one of the following statements is not true?
when magma reaches the surface, its dissolved gas content increases
the 1943 eruption of Paricutin in Mexico was characterized by ____.
cinder cone building and basaltic lava
The average composition of rocks comprising a large composite cone or stratovolcano is similar to a (an) ________ magma.
A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows.
Which of the following best describes Shiprock, a famous volcanic feature in New Mexico?
the eroded remains of a volcanic pipe and radiating dikes
The recent (geologically) volcanic activity in Yellowstone National Park is ________.
related to intraplate, hot spot volcanoes
The icelandic volcanoes are related to plate tectonics because ______.
they lie on a spreading center where two plates are moving apart
Which one of the following best describes volcanism in the Cascade Range, northwestern U. S.?
related to plate subduction
Which of the following statements best describes the big Hawaiian volcanoes?
are situated in the interior of a large, Pacific plate above a hot spot deep in the mantle
At low pressures and in the absence of water, rhyolites and granites begin to melt at about ________.
800 degrees C
What volcanic events formed Crater Lake, OR? When did they take place?
caldera collapse followed major ash and pyroclastic-flow eruptions; 6000 years ago
Which one of the following shows the correct order (left to right) of decreasing magma viscosity?
rhyolite, andesite, basalt
Why do magmas rise toward earth's surface?
magmas are mainly liquid and contain dissolved fluids such as water; most are less dense than the adjacent solid rock
A ___ is a near surface, intrusive, igneous rock body that results from local inflation of a horizontal sill?
Which of the following best describes the bedrock in the Sierra Nevada Mountains in California?