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48 Cards in this Set

  • Front
  • Back
Mid-ocean ridges account for ______ of the total volume of volcanic activity on Earth.
about 75% more
The composition of the lava erupted at mid-ocean ridges is:
The ocean crust has a layered structure which, from bottom to top, is
gabbro, dykes, lava flows
Melting of the mantle under mid-ocean ridges occurs because:
mantle rock is rising and undergoes decompression melting.
During circulation of ocean water through the ocean crust close to mid-ocean ridges:
the water becomes very hot.
B) the water becomes very mineralized

both a and b
The ecosystems that exist around hydrothermal vents/black smokers are sustained by energy from:
Mid-ocean ridges account for ___________ of the total energy released by earthquakes on Earth
less than five percent
Mid-ocean ridge earthquakes are:
shallow focus and mostly minor (magnitude 4 and smaller).
Which is the most common type of volcano found around the "Ring of Fire"?
The source of the magma generated (i.e., what melts) in subduction zones is:
peridotite of the mantle wedge
Compared to continental volcanic arcs, in oceanic volcanic arcs there is erupted a:
greater proportion of basalt and a lesser proportion of rhyolite.
The difference between the compositional spectrum of oceanic arc and continental arc lavas (previous question) is because:
B) there is a greater amount of crystal fractionation of rising magma in the continental arc setting.
C) there is interaction of rising magma with the continental crust in the continental arc setting
Both B and C
The eruption of which Indonesian volcano in 1883 produced a tsunami that killed some 36,000 people?
The 1902 eruption of Mt. Pelée produced a pyroclastic flow that killed some 30,000 people. Where is Mt. Pelée located?
The 1985 eruption of which volcano in Colombia produced lahars that killed over 20,000 people.
Nevado del Ruiz
In the 1980 eruption of Mt. St. Helens
A) the first visible sign of activity was small ash and steam (phreatic) eruptions.
B) there was about two months between the initial activity and the major, climactic eruption.
C) the major eruption produced air-fall deposits, pyroclastic flows, and lahars.
D) smaller eruptions continued for a few years after the major eruption.
E) all of A) to D).
The major eruption of Mt. St. Helens on 18 May, 1980, was triggered by:
a moderate earthquake (~M5) under Mt. St. Helens
Mt. St. Helens reawakened in late 2004 and continues to erupt. The eruptive activity has comprised
eruption of a lava dome with occasional phreatic explosions.
How many times had Pinatubo erupted in the 2,000 years prior to the 1991 eruption
four or five
This first sign of activity at Mt. Pinatubo in April, 1991 was:
The 1991 Pinatubo eruption was the:
second largest in last 100 years
The 1991 eruption of Mt. Pinatubo injected large amounts of ash and sulphur dioxide high into the atmosphere. Over the few years after the eruption this gas and ash:
caused a significant but small (<1°C) drop in global surface temperature.
Montserrat is part of the ___________ island arc
Lesser Antilles
The continuing (1995 to present) Montserrat eruption was triggered by:
intrusion of basalt magma into the magma chamber.
The lava being erupted in the continuing Montserrat eruption is:
andesite with about 60% SiO2 and 5% H2O.
The continuing Montserrat eruption has produced
air-fall, lahars, and pyroclastic flows.
Of the total energy released globally by earthquakes, what percentage is released by subduction zone earthquakes?
98 percent
Earthquakes in subduction zones occur to as deep as 700 km, but no deeper. This is because:
the subducting plate remains intact and does go deeper than 700 km in the mantle, but has released all of its stored stress by 700 km depth.
The largest magnitude subduction zone earthquakes are of:
shallow focus and occur on the boundary between the subducting and over-riding plates where there is compression.
On the Cascadia subduction zone
the recurrence interval for great, ~M9 earthquakes is about 500 years
The M7.8 Tangshan, China, earthquake in 1976 was predicted, people in the area were evacuated before the earthquake because of the prediction, and hundreds of thousands of lives were saved.
In the 1995, Kobe, Japan, earthquake
B) extensive destruction resulted from liquefaction and fires.
C) the adverse impact on the Japanese economy ran to tens of billions of dollars.
D) both B) and C).
The 26 December, 2004, Great Sumatra earthquake
) occurred on a segment of the subduction zone that had very few earthquakes in the previous 40 years.
and had a rupture length of over 1000km
Both A and C
The tsunami generated by the 26 December, 2004, Great Sumatra earthquake was recorded in the Atlantic and Pacific Oceans.
The devastating M7.6 Pakistan earthquake on 8 October, 2005, was of:
shallow focal depth and on a plate boundary thrust fault.
On transform faults that join together mid-ocean ridge segments, the actual sense of motion is the same as the apparent (from offset of the ridge segments) sense of motion.
The San Andreas transform system:
started to develop about 25 million years ago when the East Pacific Rise began to be subducted, and has since progressively increased in length.
At the "big bend" in the San Andreas fault (to the east and north of L.A.) there is:
transpression, and therefore a component of thrust faulting.
This California earthquake is significant because it triggered a large earthquake on a nearby fault.
1992 Landers
The 1994 Northridge earthquake occurred on a:
blind-thrust fault
The 1906 San Francisco earthquake
A) was of magnitude 7.9.
made almost 250,000 people homeless
Both A and C
The devastation of San Francisco in 1906 mostly was the result of collapse of buildings due to ground shaking and to a lesser extent from fires.
The speed and effectiveness of the federal government response to the 1906 San Francisco earthquake disaster and the 2005 hurricane Katrina disaster was:
much better in 1906 than in 2005
The 1906 San Francisco earthquake was the first major earthquake disaster to which the overwhelming response was a rational one that sought to understand the natural (rather than supernatural) cause of the earthquake.
There was a very large eruption in central New Mexico just over 1 million years ago that formed a large caldera called:
Valles Caldera
The cinder (scoria) cone that popped up in a Mexican corn field in 1943 is:
The earthquake hazard to San Francisco and the Bay area is from:
A) the Calaveras fault.
B) the Hayward fault.
C) the San Andreas fault.

E) All of A to C