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Exam 2 Geo
Earthquakes, Volcanos & Mass Movements
115
Geology
Undergraduate 2
10/04/2011

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Term
Creep
Definition
Slow, gradual movement along a fault
Term
Focus
Definition
the point of first break on a fault during an earthquake
Term
earthquakes orginate in the....
Definition
lithosphere
Term
Earthquake P Waves
Definition
are compressional waves
Term
Elastic Rebound Theory Explains
Definition
  • the generation of earthquakes along fault zones
  • the likely reoccurence of earthquakes along the same fault zone
  • the concept of seismic gap
Term
We Can Predict....
Definition
the regions where major earthquakes are likely to occur in the future
Term
In the US earthquake intensity is measured by...
Definition
Modified Mercalli Scale
Term
An earthquake with a magnitude of 5 on the Richter scale vs a magnitude of 7 releases how much more energy?
Definition
900 times more
Term
an earthquake with a magnitude of 5-6.9 would be described as
Definition
a moderate earthquake
Term
the problem of liquefaction could be somewhat reduced by...
Definition
installing efficient underground drainage systems
Term
Tsunamis
Definition
can travel at speeds of hundreds of miles per hour
Term
seismic gaps represent...
Definition
"locked" sections along otherwise active faults
Term
examples of earthquake pre-cursors....
Definition
  • increase then decrease in the electrical resisivity of rocks
  • changes in water levels of wells
  • anomalous animal behavior
Term
U.S. Geological Survey
Definition
US agency authorized to issue warnings of impending earthquakes and other geologic events
Term
Which nation currently DOES NOT have a government sponsored earthquake prediciton program?
Definition
Mexico
Term
South Carolina
Definition
a state at risk for a severly damaging earthquake
Term
The Phenomenon in which rocks snap back elastically to the prestress condition after an earthquake is called....
Definition
Elastic Rebound
Term
Epicenter
Definition
the point on the earth's surface directly above the focus of an earthquake
Term
seismic waves
Definition
energy released when an earthquake occurs that are divided into body wave and
surface wa
Term
S Waves
Definition
body waves that involve a side to side motion of molecules of the material in which they travel
Term
Intensity
Definition
a measure of the damaging effects of an earthquake on surface features and on humans
Term
precursor phenomena
Definition
events that precede an earthquake that can be used to predict its occurence
Term
fluid injection
Definition
a method of releasing built up strain along locked sections of faults by pumping fluid into fault zones
Term
deep focus earthquakes
Definition
are concentrated in subduction zones
Term
P Waves
Definition
first waves to be detected during an earthquake
Term
S waves
Definition
can not be detected all over the earth during an earthquake
Term
P waves
Definition
travel through matter, the matter is alternately compressed and expanded
Term
The further away a receiving seismograph is from the epicenter of an earthquake...
Definition
the greater the lag time between the arrival of P & S waves
Term
Calculation of the Richter magnitude of an earthquake is based on....
Definition
maximum amplitude of sesismic waves recorded on teh seismogram and adjusted for the distance of the seismograph from the epicenter.
Term
Earthquakes are...
Definition
NOT extremely rare events
Term
Modified Mercalli Scale
Definition
the intensity increases as the number gets higher
Term
Buildings on deep soil usually
Definition
suffer more than those built on bedrock
Term
During the 1906 San Fransisco earthquake
Definition
70% of the damage was due to fire rather than ground movement
Term
It is not possible to predict the....
Definition
timing and size of major earthquakes
Term
it is best to be ________ during an earthquake
Definition
indoors
Term
The 1989 Loma Prieta earthquake has...
Definition
increased the near-term liklihood of failure along the peninsular segment of the San Andreas fault
Term
Most earthquakes are a magnitude of
Definition
5 or less
Term
most magmas originate in the
Definition
upper mantle
Term
mafic (iron rich) lavas
Definition
are low in viscosity and flow easily
Term
most volcanic activity on land occurs
Definition
in association with subduction zones
Term
a well known volcano associated with a rift zone is ....
Definition
Kilimanjaro
Term
most volcanic rock is created at
Definition
seafloor spreading ridges
Term
The Columbbia Plateau is an example of ...
Definition
a fissure eruption
Term
The Hawaiian peak called Mauna Loa is an example of ...
Definition
a shield volcano
Term
Is not a type of pyroclastic material....
Definition
flowing lava
Term
Cinder Cones
Definition
volcanoes composed of pyroclastics
Term
Stratoyolcanoes
Definition
volcanoes of the Cascade Range
Term
the residents of Icelandic island of Heimaey stopped lava flow by....
Definition
cooling lava with water
Term
a pyroclastic outburst of a denser than air mixture of hot gases and fine ash is ...
Definition
a pyroclastic flow
Term
the catastrophe at Lake Nyos, Cameroon, Africa in 1986 was caused by....
Definition
the release of carbon dioxide
Term
volcanic erruptions may at least temporarily...
Definition
-contribute to the formation of acid rain

-decrease average global temperature

-increase the rate of ozone depletion
Term
Changes in barometric pressure
Definition
are not precursors to volcanoes
Term
seismic activity, deformation of a volcanoes surface & changes in the mix of gases emitted from a volcano
Definition
ARE precursors to a volcano
Term
Volcanologists
Definition
can anticipate the likelihood of an explosive eruption
Term
concerning responses to eruption predictions the safest course it to...
Definition
undertake precautionary evacuations
Term
subduction is the underlying cause of ...
Definition
volcanoes of the Cascade Range & Pacific Northwest
Term
Rhyolite
Definition
volcanic, fine grained compositional equivalent of granite
Term
Ring of Fire
Definition
a collection of volcanoes rimming the Pacific ocean
Term
Mount St. Helens has fored a crater known as...
Definition
an andesitic dome
Term
Pyroclastics
Definition
bits of violently erupted volcanic material
Term
Stratovolcanoes are also known as
Definition
composite volcanoes
Term
lahar
Definition
a mudflow of meltwater and volcanic ash produced by a volcanic eruption
Term
During the 1902 eruption of Mont Pelee, the town of St. Pierre on the Caribbean Island of Martinique was destroyed by
Definition
pyroclastic flow
Term
Pyroclastic flow =
Definition
huees ardentes
Term
during the A.D. 79 eruption of Mount Vesuvius many were killed by
Definition
toxic or volcanic gases
Term
if a volcano is very unlikely to erupt it is called-
Definition
extinct
Term
Caldera
Definition
an enlarged volcanic summit crater formed either by an explosion or the collapse of a volcano
Term
The eruption of Mt. St. Helens in 1980 made many Americans realize...
Definition
that they lived in areas threatened by volcanoes
Term
most volcanoes are located over...
Definition
subduction zones
Term
The most energetic pyroclastic eruptions are more typical of volcanoes with...
Definition
viscous lavas, because thicker lava tends to trap more gases
Term
an example of phreatic eruption-
Definition
the violent eruption of the Indonesian island of Krakatoa in 1883
Term
volcanic eruptions that spew sulfur-rich gas may enhance the effects of -
Definition
acid rain
Term
animals can
Definition
"foresee" volcanic events
Term
silica rich magmas are
Definition
more viscous, thicker and flow sluggishly
Term
lava flows can be harzardous however; they are ...
Definition
predictable since their flow paths can be anticipated
Term
there are an estimated ____ to ____ ACTIVE volcanoes in the world
Definition
300- 500
Term
Mount Pinatubo exhibited several precursors prior to its 1991 eruption including...
Definition
-increased seismic activity

-a bulge on the volcanoes surface

-emissions of ash

-sudden drop in gas output
Term
Mass movements occur when-
Definition
the shearing stress on the material exceeds its frictional resistance (or shear strength)
Term
All else being equal, a slope steepness increases, the shearing stress of a material
Definition
steadily increases
Term
The rockslide that buried Goldan, Switzerland in 1806 was caused by...
Definition
the steepness of slopes due to tectonic movements
Term
North Dakota
Definition
has a low overall landslide potential
Term
a pile of concrete blocks has
Definition
a greater angle of repose than a pile of marbles or a pile of apples
Term
a reduction in pore pressure
Definition
is the least likely to cause mass movement on a steep slope
Term
quick clays
Definition
consist of very fine particles held together by salty pore water
Term
The Vaiont Reservoir disaster was caused by
Definition
a landslide
Term
soil creep is often triggered by...
Definition
frost heaving
Term
frost heaving
Definition
results from ice forming beneath the surface of soil during freezing conditions in the atmosphere.
Term
the rate of motion of a landslide is commonly related to-
Definition
the proportion of moisture within the material
Term
scarp formation is often associated with
Definition
slumps
Term
snow avalanches, debris avalanches and volcanic lahars are examples of ---
Definition
flows
Term
a flow involving a wide variety of materials is called
Definition
a debris avalanche
Term
reducing the risk of landslide on an unstable steep slope can be accomplished by---
Definition
reduction in slope angle

placement of additional supporting material at the base of the slope

reduction of slope load by the removal of material high on the slope
Term
signs of creep include:
Definition
curved or tilted tree trunks
cracks in the ground surface parallel to the slope

slanted utility poles
Term
Landslide
Definition
general term for rapid mass movement
Term
Angle of Repose
Definition
maximum slope angle at which a given dry, unconsolidated material is stable
Term
Frost Hearing
Definition
is the expansion of wet soil as it freezes and ice expands
Term
Rock Flour
Definition
fine grained sediment of pulverized rock produced by glacial erosion
Term
Creep
Definition
extremly slow mass-wasting event
Term
Fall
Definition
a free-falling action in which the moving material is not always in contact with the ground underneath
Term
Talus
Definition
accumulated debris that result from rockfalls or rockslides
Term
Slide
Definition
a mass-wasting event in which a relatively cohesive unit of rock or soil moves downsloope along a well defined surface or plane
Term
Soil Slump
Definition
a slide that typically exhibits a rotational movement of soil as it moves downslope
Term
Flow
Definition
mass-wasting event in which materials move in a chaotic, incoherent fashion
Term
The most rapid mass movements are normally-
Definition
rockfalls, avalanches & mudflows
Term
landslides are often triggered by heavy rain or
Definition
earthquakes
Term
the force behind mass movements is
Definition
gravity
Term
Portuguese Bend in Los Angeles County, CA. is an example of
Definition
a slide area activated by humans
Term
artifical reservoirs can cause landslides by
Definition
increasing pore pressures in rocks along the sides of the reservoirs
Term
the most rapid mass movements can travel at speeds of
Definition
hundreds of kilometers per hour
Term
the most successful retaining walls are-
Definition
low and thick
Term
aerial photography can be used to identify
Definition
inconspicuous mass movements
Term
angle of repose is less for
Definition
smooth rounded particles
Term
creep
Definition
rarely threatens lives
Term
a snow avalanche is a type of
Definition
flow
Term
moisture reduction techniques work best where
Definition
rocks or soils are relatively permeable
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