Chapter 4,5,6,7 Natural Disasters
Three basic classes of collisions are
Continental plate versus mantle plate
__________ melting occurs when a rock melts due to a lowering of pressure.
Decompression
At oceanic spreading centers, magmas are rhyolitic in composition.
False
Earthquake epicenters east of the Rocky Mountains are in random locations and do not cluster in certain areas.
False
Spreading ridges produce the largest number of great earthquakes.
False
The biggest disasters occur when great earthquakes occur at great depths.
False
The higher the viscosity of magma, the more fluid is its behavior.
False
The primary cause of deaths in earthquakes in modern times is people being swallowed alive by the ground, rather than by building collapse.
False
The most peaceful eruptions are __________ eruptions.
Icelandic type
Several recent earthquakes in Washington's Puget Sound region were caused by movement of the subducting ______________ Plate.
Juan de Fuca
__________ eruptions are the most violent types of explosive eruptions.
Plinian-type
Spreading centers have relatively peaceful eruptions of magma because the __________.
SiO2-poor magma is at high temperatures.
__________ are steep-sided, symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.
Stratovolcanoes
Magma at great depth does not contain gas bubbles because the high pressure at depth keeps gas dissolved in solution.
True
The basaltic magmas that erupt on the ocean floor have a low SiO2 content, high temperature, and allow gas to escape easily, all resulting in non-explosive eruptions.
True
_________ eruptions are common first phases in the eruptions of volcanoes as they "clear their throats" before emitting larger eruptions.
Vulcanian-type
In the 1989 Loma Prieta quake, the Marina District building collapses were extensive, and numerous destructive fires broke out, due to all but which one of the following?
Widespread looting and arson
A caldera collapse occurs ________________.
after the magma chamber is mostly empty
Pyroclastic debris is __________.
chucks of magma and rocks blown into the air by gas in a volcanic eruption
A well-formed conical volcano located above an active subduction zone that has not erupted in 12,000 years is __________.
dormant, but will likely erupt again at some point
When a number of earthquakes along in the same general area over the course of a few months or years, the event is referred to as an
earthquake cluster
The ongoing collision between Asia and the subcontinent of India is resulting in
great earthquakes over a gigantic area
Shallow subduction zone earthquakes occur
in the upper portion of the down-going plate, at the bend in the subducting plate, and in the overriding plate
Which of the following can help make rocks melt beneath Earth's surface?
increasing temperature and decreasing pressure
Constraining bends in large strike-slip faults commonly "lock up"; thus, movements there tend to be
infrequent and large
In San Francisco's Marina district in 1989, some fill underwent permanent deformation and settling, and some formed slurries as underground water and loose sediment flowed like a fluid in a process known as
liquefaction
Rock may melt by _______________.
lowering the pressure on it, raising its temperature, and increasing its water content
The presence of water ________ the melting point of rock.
lowers
Lava Flows
molten rock moving downslope
Earthquakes in Hawaii are mostly related to ________________.
movement of volcanic magma beneath the ground
Lahars
muddy water-laden rush of material downslope
The dominant type of faulting in the Great Basin region is ______________.
normal faulting
The typical trend in a rising plume of subduction-zone magma is to increase the ____________.
percentage of SiO2, viscosity, and explosive potential of the magma by holding in the gases more tightly
pyroclastic flow
rapid rush of gases and materials downslope
The New Madrid earthquakes are apparently related to an old buried ____________.
rift zone
The seismic-gap method of earthquake forecasting works by identifying
segments along a fault that not moved for the longest amount of time
What is the cause of volcanism at Italy's Vesuvius, Stromboli, Vulcano, and Etna?
the subduction of Mediterranean seafloor beneath Europe
The three 'Vs' of volcanology are __________________.
viscosity, volatiles, and volume
Liquefaction occurs when seismic waves cause
water to be injected into sediment causing the grains to lose cohesion and behave like a fluid
In magma, __________ is the most abundant dissolved gas.
water vapor (H2O)
The greatest earthquakes in the world occur
where plates collide with each other
A shield volcano has a great ___________.
width compared to its height
