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Terms in this set (100)
When is a large event such as an earthquake not a disaster?
when it happens in an area without any people
What is a reason people live in geologically dangerous areas?
for the view
land is fertile, productive for farming
the land is cheap
When an insurance company decides on the cost of an insurance policy for a natural hazard, the two primary deciding factors are the probability of the occurrence of an event and the cost of the probable loss from the event.
Which is NOT a way that government policy mitigates natural hazards?
organizing central emergency management agencies to bring order to chaotic relief efforts
The costs of catastrophic events continue to increase primarily because:
more people are moving into more hazardous areas.
Who is most commonly to blame when people incur a significant loss from a natural disaster?
the people themselves for choosing to live there
Natural disasters generally involve which of the following?
events that involve overlapping natural causes
Which of the following is an example of a counterproductive governmental policy to mitigate natural disasters?
Congress funds the Army Corps of Engineers to replenish sand on beaches without addressing the reason for the beach erosion
What is the most deadly hazard in the United States?
heat and drought
If the recurrence interval for a stream flood has been established at 50 years and the stream flooded five years ago, what is the probability of the stream flooding this year?
1 in 50
If the Atlantic Ocean floor is getting wider, why is the Earth not becoming larger?
Old ocean floor sinks at subduction zones (trenches).
Which of the following is true?
Rift zones are areas where oceanic crust is formed.
Which of the following is true concerning Earth's lithosphere?
It is the stiff, rigid outer layer of Earth.
Which of the following is true concerning Earth's asthenosphere?
Compared to the lithosphere, the asthenosphere is weak, hot, and occurs farther from Earth's surface.
The Mid-Atlantic Ridge represents which type of plate boundary?
rift or spreading boundary
Which type of plate boundary lies below the Cascade Mountain Range in North America?
The San Andreas Fault represents which type of plate boundary?
Volcanoes occur most often along divergent plate boundaries on the ocean floor.
Relative to the Mid-Atlantic Ridge, where is the oldest crust located beneath the Atlantic Ocean?
At the edge of the oceanic crust where it begins to subside under the continental crust.
Why does oceanic lithosphere almost always sink beneath continental lithosphere at convergent zones?
The oceanic lithosphere is denser and heavier than continental lithosphere.
How much greater is the amplitude of a Richter magnitude 6 earthquake compared to a magnitude 4 earthquake?
What is the approximate highest frequency of vibration (of back and forth shaking) in earthquakes?
20-30 cycles per second
Which type of soil would NOT be subject to liquefaction during an earthquake?
dry soils with little to no water
What type of fault occurs along a divergence boundary where the relatively higher rocks near the fault occur below the plane of the fault?
What type of fault occurs where the elevation on each side of the fault is the same and the rock on either side of the fault slips laterally past one another?
What type of fault occurs along a convergent boundary where the rocks on the higher-elevation side of the fault occur above the plane of the fault?
Prior to an earthquake, rocks across a fault are stressed and bent elastically. During the earthquake, the rocks fracture, and the rocks on either side of the fault return to their original shape but offset across the fault. What is the name of this theory for how earthquakes occur?
elastic rebound theory
The Cascadia fault along the west coast of North America is an example of what type of fault or boundary?
onvergent subduction boundary
Order seismic waves from the fastest to the slowest. In other words, order the earthquake waves according to which wave arrives at a location first, second, and last.
P waves, S waves, surface waves
Which seismic wave has the greatest amplitude?
The epicenter of an earthquake describes the location where a fault first slipped and can occur at any depth, while the focus of an earthquake describes the location on Earth's surface above the epicenter.
Which factors directly affect the size of an earthquake?
offset, rupture length, and type of fault
The largest magnitude earthquake on record occurred in _______ (magnitude 9.5) in association with a _______ boundary.
What characteristic of earthquakes does a seismograph measure?
Which of the following is true concerning the Mercalli Intensity Scale?
This scale is based on how much people feel shaking and on damage.
With increasing magnitude on the Richter scale from 1 to 10, the violence of shaking, time of shaking, and area experiencing shaking continually increase.
The moment magnitude is a measure of what characteristic of earthquakes?
the energy released
A Richter magnitude 4 earthquake releases how much more energy than a magnitude 3 earthquake?
Which of the following scenarios would cause the largest amplitude shaking and the longest time of shaking at a location 50 km from the epicenter of an earthquake?
A fault 5 km below ground slips 2.5 m
The 1994 earthquake in Northridge, CA, occurred on along the _______ fault and raised the city of Northridge by _______.
Pico thrust, 20 cm
Why do parking garages often fail and fall during an earthquake?
Horizontal support beams shake off their vertical columns because they are often not well braced.
Buildings sway back and forth in an earthquake. A 20-story building oscillates how often?
once per 5 seconds
What commonly causes severe damage in single-story frame (wood construction) houses in an earthquake?
They shake off their foundations.
Which is a major fault that often shows a progressive migration along its length with time?
the North Anatolian Fault in Turkey
Areas of cities that are subjected to significant natural hazards such as earthquakes should be used for which of the following?
parks and natural areas
What is a seismic gap?
part of a fault that has not had recent earthquakes, even though adjacent parts of the fault have had earthquakes
The Iquique, Chile earthquake (magnitude 8.2) on 1 April 2014 was associated with only 6 deaths, while the magnitude 7 Port-au-Prince, Haiti earthquake on 12 Jan. 2010 killed ~159,000. What was the primary reason why there were so many more fatalities with the Haiti earthquake despite its weaker magnitude earthquake?
Buildings were more poorly constructed in Haiti.
What feature is sometimes used to prevent a building from shaking too much during an earthquake?
base isolation using thick rubber pads
______ is/are NOT effective in earthquake prediction.
Changes in tide heights
What is the likely reason that government agencies might fail to act on an earthquake prediction?
Emergency measures and evacuation are costly and may be irresponsible if the prediction is inaccurate.
The most significant information for forecasting high earthquake probability is that a segment of the fault _______.
has had very few significant earthquakes in the recorded past
The best known successful prediction of an earthquake was in ______.
Haicheng, China (1976)
The Loma Prieta earthquake in 1989 occurred on which fault?
improves forecasting of earthquakes by extending knowledge before written records
Which of the following is true about the recurrence interval?
It is used to assess the average amount of time between major earthquakes in a single area.
Which of these states is LEAST at risk for earthquake hazards?
Which countries are at the highest risk for major earthquakes?
those in southern Europe
The frequency-magnitude relationship predicts that any 100 km segment of the San Andreas Fault should experience an earthquake magnitude of 6 on average (enough to cause property damage) every _____ years.
The faults around Los Angeles County at the present time ______.
are likely to rupture, since they have more energy stored in slippage than has been released in earthquakes
In an earthquake, what are you most likely to be injured from?
objects falling on you
A basalt magma typically erupts in what form?
A big bulge sometimes slowly grows on the flank of an active Cascades volcano. Why?
Rising magma is pushing it up
If you see a large, steep-sided volcano in the distance (e.g., High Cascades), what type of volcano is it and what is the rock composition?
a stratovolcano made of andesite lava flows and ash
What two main factors result in more violent eruptions?
more water and higher viscosity of the magma
Which of the following statements about volatiles is true?
Water content determines the violence of a volcanic eruption.
Eruptions dominated by basalt compositions are found where?
along divergent boundaries at mid-oceanic ridges
Highly explosive magmas are controlled by which of the following?
high silica content and high water
Which combination of factors can cause solid rock to melt into magma?
increase water content and increase temperature
How is a caldera different from a crater?
A caldera is formed by sinking land after an eruption, while a crater forms as ash is blasted out
What type of volcano typically forms over a subduction zone?
a composite volcano
Which of the following statements about basalt is NOT true?
Basaltic magmas have the highest volatile content.
What are the two most abundant gases in magmas?
water vapor and carbon dioxide
When comparing the characteristics of common magmas or lavas, ______.
rhyolite has the highest viscosity
Which type(s) of magma result in erupted material that is mostly in the form of ash?
What characteristic of a subduction zone is most influential in generating magma and/or a volcano?
high water content in the rock of the subducting slab
The ropy, basalt-rich, and steam-charged lava flows found in volcanoes like Kilauea are called ______ lava.
Why are pyroclastic flows dangerous?
They move very fast and extend over a long distance.
A resurgent dome ______.
forms inside of a continental caldera
Rift zones where a volcano spreads in different wedge-shaped sections are characteristic of which type of volcano?
What is the name of the volcano that erupted in 1620 BC and destroyed the town of Akrotiri, possibly the source of the Atlantis legend?
A big bulge sometimes slowly grows on the flank of an active Cascades volcano. Why?
Rising magma is pushing it up.
Which of these is NOT a Cascade volcano of western North America?
What is the best way to avoid a mudflow?
Climb up the valley wall.
Following the May 1980 eruption of Mount St. Helens, Washington, thousands of trees lay on the ground, all parallel to one another. Why?
A lateral blast at the beginning of the eruption blew them all down.
If an ash flow approaches you from across a kilometer-wide lake, are you likely to be safe or not? Explain why.
Not safe. Ash flows can cross much wider bodies of water.
In contrast to an old ash-flow deposit, an old ash-fall tuff does NOT include which of the following?
differences in thickness based on valleys and hills
Volcanic mudflows are caused when which of the following combine?
ash and water
What is tuff?
ash after deposition forms a rock
The first tiltmeters were simple levels made with water tubes __________ long.
Three Sisters are located just west of which city?
Lava flows _______.
move slowly enough that they are usually a threat only to property
Which of the following is TRUE concerning pyroclastic flows?
These flows can reach temperatures so hot that they glow.
Which of the following conditions increases the danger of volcanic ash the MOST?
The volcano creates rain, making building collapse far more likely.
What is the PRIMARY reason that volcanic ash poses a hazard to aircraft?
Ash melts when sucked into jet engines, coating parts of the engine, and causing it to fail.
Which of the following is TRUE concerning the loss of property and life due to volcanoes?
They depend on the products produced by the eruption and the population density near the volcano.
Which odorless, invisible gas can be the MOST dangerous gas emitted by a volcano (i.e., can directly cause the most fatalities)?
What are harmonic tremors?
weak earthquakes that precede an eruption
Attempts to slow or divert lava flows have only been partially successful. But, which of the following techniques has shown the MOST promise or been the most effective in controlling lava flows?
using water to harden the edges of the flow
Which Italian city is dangerously located between two recently active volcanoes?
Why is the threat of volcanic disaster from volcanoes in the Cascades less than that from Mt. Vesuvius?
Proper land-use planning has designated the areas around the Cascades as national parks.
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