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Environmental Geology (Ch. 5, 6, & 8)

Terms in this set (112)

How are the magnitude and frequency of natural hazard events typically related?
Inversely related
How does a catastrophe differ from a disaster?
Damages from a catastrophe are of such a magnitude to require a long recovery period
Why is history important in understanding natural hazards?
most natural hazards are repetitive events
Why are precursor events important?
precursor events provide warning that a hazardous process is becoming active
Why are hazard warnings sometimes problematic?
Warnings are occasionally inaccurate
To what does the concept of acceptable risk refer?
the risk that society or individuals are willing to endure
How is the risk of a particular event defined?
risk is the probability of occurrence of an event multiplied by its consequences
What is the difference between reactive response and anticipatory response?
A reactive response has to do with recovery, while an anticipatory response has to do with preparedness
Why is land use planning typically more effective than artificial control of natural hazards?
most hazardous natural processes are not amenable to artificial control
Why might global climate change impact the magnitude and frequency of hazardous events
many hazardous natural events are controlled in part by the amount of water in the system
Why might global warming increase the magnitude and/or frequency of weather-related hazards?
warmer ocean waters will channel more energy into the atmosphere
Why does population increase affect the number of catastrophic events?
greater numbers of people occupy marginal lands in the path of hazardous processes
Which of the following did not claim more than 250,000 lives?
Hurricane Katrina
What Columbian volcano provided lessons concerning the dissemination of scientific predictions of natural hazards
Nevado del Ruiz
Frequency
the recurrence interval of an event
Catastrophe
disaster from which recovery is long and involved
Benefits of volcanism
enrichment of soils/creation of new land
Acceptable risk
the potential for disaster that a society or individual is willing to endure
Hurricane Mitch was magnified by...?
deforestation
Magnitude
the amount of energy released by an event
How does earthquake magnitude differ from intensity?
magnitude reflects energy release while intensity reflects the amount of shaking
On what basis are mercalli intensity values assigned to loactions?
qualitative perceptions of and structural repsonse to the shaking
The new madrid earthquakes were different from most CA earthquakes because
the new madrid earthquakes were centered in a plate interior
A strike slip fault has what type of motion
horizontal
active fault
a fault that has experienced movement during holocene time
surface waves are produced by
p- and s-waves reaching the surface
why are nearby earthquakes often described as "jolting" while distant earthquakes are described as "rolling"
because high frequency waves are attenuated as they move away from the epicenter
During the strain accumulation phase of the earthquake cycle
rocks are deformed elastically
how can injection of liquid wastes cause earthquakes
it increases fluid pressure and reduces friction
tsunamis are generated by
vertical displacement of ocean water
ground rupture occurs during an earthquake as
a near-surface fault breaks the surface
Why did the tanshan earthquake in china deal a blow to the chinese earthquake prediction program
it occurred without foreshocks and was not predicted unlike one the previous year
Why might the emission of radon gas be useful in prediction earthquakes
fracturing of the rocks allows radon to move more readily
Why have the 20th century earthquakes in turkey suggested that some earthquakes beget subsequent earthquakes
earthquakes have occured in a pattern from east to west
the major goal of the US earthquake hazard reduction program is to
reduce earthquake hazards through understanding of risks and prediction of hazards
Most large earthquakes in the US are interplate earthquakes
TRUE
Buried faults are typically associated with folds in sedimentary rocks
TRUE
P-waves travel faster than surface waves
TRUE
depth of focus is an important factor in determining the intensity
TRUE
Tsunamis can cause damage thousands of miles from their source
TRUE
Richter magnitude
is determined from the amplitude of waves recorded on seismograms
new madrid and charleston earthquakes were....
intraplate earthquakes
Thrust fault
type of reverse fault with a gentle angle of dip
Inactive fault
has not experienced movement in the last 2 million years
Elastic rebound
the process that releases elastic strain during and after an earthquake
Liquefaction
the transformation of saturated sediments from the solid to the liquid form
China issued...
the first successful short-term earthquake prediction in 1975
Seismic Gap
an area along an active fault zone that is likely to produce large earthquakes, but has not done so recently
Earthquake from 2010 that killed hundreds of thousands of people
Haiti
Paleoseismology
the study of past earthquake history from trenches along faults
Why are most active volcanoes associated with plate tectonic boundaries?
Spreading or sinking plates interact at plate boundaries with other materials to produce magma.
Viscosity of a magma is controlled by
temperature and silicon content of the magma
The shape of shield volcanoes is a function of
lava viscosity
Why do composite volcanoes consist of alternating lava and pyroclastic layers?
Composite cones are created by a mixture of explosive activity and lava flows
Mid-ocean ridge volcanism produces what type of volcanic rock?
basalt
Composite cones typically are associated with what type of plate tectonic feature?
subduction zone
What is the principal difference between craters and calderas?
Calderas are much larger depressions created by collapse of the upper portions of the volcano
Why were the citizens of Heimaey, Iceland, successful in stopping the lava flow that threatened their harbor?
They had a ready supply of water with which to chill the lava.
What is one reason that ash fall is such a significant hazard
The weight of the ash can cause structural damage to buildings
A lahar is produced when
ash and other pyroclastic ejecta become saturated with water
Hundreds of residents near a dormant volcano at Lake Nyos died when
a dense cloud of volcanic gas was released
The number of fatalities from the Mt. Pinatubo eruption was relatively low because
the eruption was predicted successfully, and the area was evacuated
Seismic activity serves as a tool of volcanic forecasting because
moving magma causes earthquakes
Why is the geologic history of a volcano important in hazard prediction?
The geologic history reveals the frequency and style of eruptions.
Why is topographic monitoring sometimes useful in forecasting a volcanic eruption?
A volcano sometimes swells as lava moves into the edifice.
Viscosity
a primary control on the nature of volcanic activity.
Composite volcanoes are typically associated with subduction zones.
TRUE
The 1991 eruption of Mt. Pinatubo cooled the Earth's climate the following year.
TRUE
The citizens of Heimaey, Iceland, succeeded in stopping a lava flow from blocking their harbor.
TRUE
Mt. Unzen
in 1991 killed several tens of people with pyroclastic flows.
Shield volcanoes typically consist of the rock type ________.
basalt
Volcanic domes typically consist of the rock type ________
rhyolite
Cinder cones
small volcanoes formed from tephra accumulation near a volcanic vent
Ash flows or Pyroclastic flows
dangerous, hot masses of ash and gas that travel down the flanks of a volcano.
Sulfur Dioxide
a volcanic gas associated with acid rain and vog
the eruption of st. helens began with a massive
landslide
Lahars
volcanic mudflows
At Lake Nyos
a dense cloud of gas was released from a volcanic crater, flowing down the volcano and killing hundreds of people.
Ash fall
a tremendous quantity of rock fragments, natural glass fragments, and gas is blown high into the air by explosions from the volcano
caldera eruption
relatively infrequent large volcanic eruption that is associated with a catastrophic explosion that may produce a very large volcanic crater 20 or more km in diameter
lateral blast
explosions of gas/ash from the side of a volcano that destroy part of the mountain
lava
magma that has emerged from a volcano onto earth's surface
magma
molten rock
shield volcanoes
the largest volcanoes, shaped like an arch or shield, characterized by generally non-explosive eruptions which result from relatively low silica content of the magma
volatiles
chemical compounds that evaporate easily and exist in a gaseous state at earth's surface
volcanic dome
viscous magma with a relatively high silica contect
List the major types of volcano and the type of magma associated with each
shield volcano - basalt

composite volcano - andesite

volcanic domes - rhyolite

cinder cones - basalt
List the major types of volcano and their eruption style. Why do they erupt the way they do?
shield volcano - erupts quietly, producing lava flows

composite volcano - erupts both quietly and explosively, producing lava flows and pyroclastic deposits

volcanic domes - explosive

cinder cones - mildly explosive

**eruptive style is governed largely by viscosity and gas content
What is the relationship between plate tectonics and volcanoes?
most volcanoes are associated with plate tectonic boundaries, particularly divergent margins and subduction zones, hot spot volcanoes form in plate interiors
List the primary and secondary effects of volcanic eruptions.
primary effects: lava flows, pyroclastic activity, and gas release

secondary effects: lahars, floods, fires, global cooling
What are the major gases emitted in a volcanic eruption
CO2, CO, water vapor, sulfur dioxide, hydrogen sulfide
Earthquake
when stress on the rocks exceeds their strength, the rocks rupture, forming a fault and producing an earthquake
Earthquake cycle
the earthquake cycle proposes that there is a drop in elastic strain after an earthquake and there is a re-accumulation of strain before the next event
epicenter
the location on the surface of EARth about the focus
Fault
a fracture or fracture system along which rocks have been displaced
fault zone
a group of related faults roughly parallel to each other in map view
focus
the point at depth where the rocks ruptured to produce the earthquake
moment magnitude
a measure of the energy released by the earthquake, and is based upon important physical characteristics, including the seismic moment, the area that ruptured along a fault plane during an earthquake, the amount of movement or fault slip during an earthquake, and the rigidity of the rocks
P wave
faster than s waves and can travel through solid, liquid, and gaseous materials

compressional (pushing and pulling rock particles)
shake map
a map which shows the extent of potential damaging shaking following an earthquake
surface wave
when seismic waves reach the surface, complex surface waves are produced
s wave
can only travel through solid materials

shear waves (up and down and side-to-side motion perpendicular to the direction of wave travel)
Major types of faults
strike slip (left lateral/right lateral)

dip slip (normal, reverse, and thrust)
What is the difference between an anticline and a syncline?
anticline - fold upward

syncline - fold downward
tectonic creep
the movement, usually relatively constant, of 2 fault blocks along a fault without felt earthquakes
material amplification
the increase of wave amplitude by unconsolidated sediments
How has human activity caused earthquakes?
construction of dams/reservoirs, injection of liquid wastes, and creation of nuclear explosions
Forecast
unlike a prediction a forecast has ranges of certainty
magnitude-frequency concept
there is generally an inverse relationship between the magnitude of an event and its frequency
natural disaster
when 10 or more people are killed, 100 more people are affected, a declaration of emergency is issues, and a request is made for international assistance
prediction
involves specifying the date, time and size of the event
What is some of the methods of predicting where a disaster is likely to occur?
Some methods include identifying the location where a hazardous event will likely occur, determining the probability that an event of a given magnitude will occur, and observing precursor events.
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