mastering in geology part 2 part 2
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.
Which kind of eruptive activity is most likely to be highly explosive?
Eruptions of big, continental margin, composite cones or stratovolcanoes.
________ tend to increase the explosive potential of a magma body beneath a volcano
High viscosity and dissolved gas
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.
What is the largest, known volcano in the Solar System?
Olympus Mons, Mars
Basalt is the most common magma erupted along oceanic rift systems.
True
________ are usually the most abundant gases emitted during basaltic volcanism.
Water and carbon dioxide
The Columbia Plateau in Washington and Oregon is ________.
a flood basalt plateau
Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble?
aa
Mount St. Helens is ________.
an explosive stratovolcano
The average composition of rocks comprising a large composite cone or stratovolcano is similar to a (an) ________ magma.
andesite
Which of the following statements best describes the big Hawaiian volcanoes?
are situated in the interior of a Pacific plate above a hot spot deep in the mantle
Kilauea and Mauna Loa are ________.
basaltic shield volcanoes
small basaltic cones built during one, short, eruptive episode
cinder cones
Aa flows are generally thinner and have smoother surfaces than pahoehoe flows.
false
In general, cinder cones are much larger than shield volcanoes
false
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 eruptions
The recent (geologically) volcanic activity in Yellowstone National Park is ________.
related to intraplate, hot spot volcanism
Which one of the following best describes volcanism in the Cascade Range, northwestern United States?
related to plate subduction
Which one of the following shows the correct order (left to right) of decreasing magma viscosity?
rhyloite, andesite, and basalt
A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows.
shield
the big volcanoes of Hawaii
shield volcanoes
massive, gently sloping volcanoes built of successive, basaltic lava flows
shielded volcano
large, fairly steep-sided cones composed of lavas and pyroclastic layers
strato volcano
the volcanoes of southwestern Alaska and the Aleutian Islands
stratovolcano
Which region has the greatest concentration of currently active volcanoes?
the circum-Pacific area
The Icelandic volcanoes are related to plate tectonics because ________.
they lie on a spreading center where two plates are moving apart
Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be covered by flood basalts.
true
Vents that emit only heated volcanic gases and water are called fumaroles.
true
