GEOL exam 2
which of the following is NOT a typical problem of erosion by tsunamis?
erosion creates waterfalls in coastal river channels, making navigation by boats dangerous
if a volcanic eruption is predicted for your area, what is the best course of action?
evacuate
the primary human adjustment to volcanic activity is
evacuation
a river below flood stage can erode and transport more materials than the same river above flood stage true or false
false
because flash floods are of short duration, they are not hazardous true or false
false
caldera eruptions result in towering volcanic mountains true or false
false
human activities are making tsunamis more common and larger true or false
false
northern Cali., Oregon, and Washington state has one of the highest threats from tsunamis in the world true or false
false
people who live near a dam will never have to worry about flooding true or false
false
ships in the open ocean can detect the passage of a tsunami true or false
false
tectonic plates move around on an underground ocean of magma true or false
false
the area around Mt. St. Helen is now safe because the volcano is finished erupting and will stay dormant true or false
false
volcanoes associated with high viscosity magma are usually less dangerous than those with more freely flowing magma true or false
false
of the three classes of tephra- ash, lapilli and bombs- bombs pose the greatest danger true or false
false- ash does
units of discharge
feet cubed per second ft^3/sec
volcanoes are linked to other natural hazards such as (4)
fire, earthquakes, landslides, and climate change
the first step in floodplain regulation is (hint: mapping)
flood hazard mapping
primary effects of a tsunami are: (2)
flooding and erosion
the best solution to minimizing flood damage is
floodplain regulation
what is the stage of a river
height of water that is flowing
mafic rock crystallizes from (high/low) temp?
high
what type of magma is in a lava dome?
high viscosity (andesitic), low volatiles
in what environment would you find the most explosive volcanoes? (hint: ___________ on land)
hotspots on land
which homes built on the floodplain are most likely to sustain the greatest damage
houses within the 20 year floodplain
construction of a dam can significantly change the
hydrology and flood frequency and magnitude downstream
adequate preparation includes (tsunami)
improved perception of the hazard, development of ways to alert the public, preparation and implementation of a tsunami-readiness plan, and promotion of community awareness and education concerning the hazard
after a watershed is urbanized, flood discharges typically...
increase
land use changes, especially urbanization, have
increased flooding in small drainage basins by covering much of the ground with impervious surfaces, such as buildings, parking lots, and roads, thereby increasing the runoff of storm water
which of the following is NOT an effect that can be caused by tsunamis?
increased volcanic activity
urbanization increases flooding risk by decreasing what?
infiltration
flash floods in small drainage basins can be produced by
intense, brief rainfall over a small area
why do most of the world's explosive volcanoes occur along the Ring of Fire?
it's a great big subduction zone
as a tsunami wave approaches the coast, what increases?
it's amplitude
where can floods occur?
just about anywhere there is water, and much of the US faces the possibility of flooding
what effects might be seen in a volcanically active area even if a volcano does NOT actually erupt?
landslides and poisonous gases
what is the best reason why most lava flows aren't a threat to human life
lava flows usually don't flow very quickly, so people can outrun them
floods produce primary effects such as
loss of life and damage to structures by floodwaters
felsic rock crystallizes from (high/low) temp?
low
river flooding is the most universally experienced...
natural hazard
tsunamis are linked to other
natural hazards
which shorelines are at greatest risk for tsunamis? (near which kind of zones)
near subduction zones
flooding: the natural process of...
overbank flow
what is the greatest hazard to people in a flash flood?
people driving during the floods who get swept away in their cars
volcanic activity is directly related to
plate tectonics
property damage is much greater than in
preindustrial societies because floodplains in industrialized countries are often extensively developed
tsunamis can move...
sediments and nutrients inland with long-term ecosystem benefits
which region has the LEAST risk for tsunamis?
shorelines in the Atlantic ocean
the largest tsunamis generated by earthquakes are produced at:
subduction zones
andesitic magma is most commonly found at what type of plate tectonic setting?
subduction zones (convergent)
forecasts of eruptions have been
successful (particularly for Hawaiian volcanoes and Mount Pinatubo in the Philippines)
drainage basin/watershed
the region drained by a stream
urbanization has several impacts on the natural processes of flooding along a river. Building or paving over land creates an impervious or impermeable surface that increases...
the runoff directly into the river, thereby increasing the flooding
most volcanoes are located at plate boundaries, where magma is produced in the...
spreading or sinking of lithospheric plates
downstream floods in major rivers are produced by
storms of long duration over a large area that saturate the soil, increasing runoff from thousands of tributary basins
a tsunami is produced by
the sudden vertical displacement of ocean water
whether a river is eroding or depositing is directly related to...
the velocity of flow
discharge refers to
the volume of water moving past a particular location in a river per unit of time
why do cinder cone volcanoes have steep slopes?
they are made from pyroclastic materials that pile up near where they were erupted
which natural hazard is NOT caused by volcanoes?
tornadoes
at what tectonic plate settings are volcanoes typically NOT found?
transform fault
Rivers normally stay in a state of dynamic equilibrium between their flow velocity, their gradient, and their cross-sectional area. true or false
true
a river in flood stage can erode and transport more sediment than the same river in normal flow true or false
true
all areas of the US have some risk of flooding true or false
true
channelization is one of the more drastic solutions to flooding because it can cause the draining of wetlands, which can have a negative impact on the wildlife true or false
true
composite volcanoes can have a long dormant period in which people may forget that they were ever once active volcanoes true or false
true
heat from volcanic areas can be used to generate electrical power true or false
true
if a basaltic lava flow were coming toward you, you could probably outrun it true or false
true
if the discharge of a river is constant and the river channel suddenly narrows or is restricted, then the velocity of the river will increase true or false
true
meandering rivers migrate over time across their floodplain and actually create their floodplains by eroding and depositing sediment over time true or false
true
occurrences of tsunamis are not influenced by human activites, but we can take actions to reduce their potential impacts true or false
true
the bed load of a stream involves the largest grains in the stream true or false
true
there is always a lag time between the time of peak precipitation and the time of peak discharge of a stream true or false
true
water returning to the ocean following tsunami inundation can cause as much damage as the run-up of the incoming water true or false
true
lava flows do not represent a serious hazard for loss of life true or false
true -because they can often be avoided; but loss of property and land can result from lava flows
lava it's _________ and ___________ are important in determining the eruptive style of the different types of volcanoes
viscosity volatile content
pyroclastic hazards include
volcanic ash falls, which may cover large areas that can destroy some structures and ruin the agricultural land, but the loss of life is less common -when these travel at very high velocities, and are extremely hot, they can destroy and kill everything in its path
where does tephra come from?
volcanic rock and lava blasted into the air or carried by gases
a "runup map" shows where
water rose during a specific tsunami event or series of events
what is avulsion
when a river shifts its position after a flood
is it possible to predict the arrival time of a tsunami in distant areas after a major earthquake?
yes
in the past50 years, have there been any deaths attributed to a volcanic eruption?
yes, thousands of people have died as a result of an eruption
which of the following describes the tsunami in Lituya Bay, Alaska in 1958?
M 7.7 earthquake triggered a massive landslide, which fell into the water and caused water to surge over 500 m above the normal water level
magma comes from melting of the...
asthenosphere
which magma has the lowest amount of silica and therefore the lowest viscosity?
basaltic
list magma types in order of increasing viscosity (least viscous first)
basaltic, andesitic, rhyolitic
what would increase during a flood, discharge or velocity?
both discharge and velocity will increase because there is more water flowing and it is flowing faster
flooding magnitude and frequency are difficult to predict on many streams because of
changes in land use and limited historical records
low viscosity (basaltic) and high volatiles are associated with what kind of volcano?
cinder cone volcanoes
secondary effects of volcanic activity include
debris flows and mudflows, -these flows can devastate an area many kilometers from the volcano
strategies are available to minimize the tsunami hazard including: (7)
-detection and warning -structural control -construction of tsunami run-up maps -land-use practices -probability analysis -education -achieving tsunami-ready status *** detection and warning system is most important
what is the difference between a crater and caldera? (What are they formed from?)
-calderas are formed from explosions -craters are formed from inward collapse of volcano tops
large calderas
-created by infrequent, huge, violent eruptions -explosive beginning; often resurge and may present a volcanic hazard for a million years or longer
rivers carry chemicals in their ______________ loads and sediment in their __________ loads
-dissolved loads -suspended and bed loads
channelization: goals are: (3)
-engineering technique: straightening, deepening, widening, cleaning, or lining existing stream channels -goals: controlling floods or improving drainage and modifying a natural stream channel
what distinguishes flash floods from downstream floods? (hint: where do they occur?)
-flash floods occur in the upper part of the drainage basin -downstream floods occur in the lower part of a drainage basin
magma is found where? lava is found where?
-inside of the Earth -outside of the Earth
shield volcanoes size? where are they common? characterized by...?
-largest volcanoes -common at mid-ocean ridges (Iceland) and over mid-plate hot spots (Hawaiian Islands) -characterized by relatively nonexplosive lava flows of basalt
stratovolcanoes
-most explosive volcanic eruptions -occur above subduction zones, particularly around the Pacific Rim -composed primarily of silica-rich lavas, such as andesite, and pyroclastic deposits
we can detect distant tsunamis in _____________ and accurately estimate their time to within a ______________
-open ocean -few minutes
why don't boats in the open ocean notice a tsunami approaching? tsunamis are too ________________ in the open ocean and the distance between _________ is too large for boats to notice their passing
-small in amplitude -crests
volcanic domes (aka lava domes)
-smaller than stratovolcanoes but develop similarly above subduction zones and are composed of viscous magma -can be explosive or non-explosive
______________ form a basic transport system of the rock cycle and are a ________________ agent in shaping the landscape
-streams and rivers -primary erosion
although flooding causes many deaths and much damage, it does provide natural service functions such as: (3)
-the production of fertile lands -benefits to aquatic ecosystems -maintenance of ample (plentiful) sediment supplies to naturally subsiding deltas such as the Mississippi
if someone bought a house just inside the 100-year flood plain, what is the chance that they will experience a flood this year?
1 in 100, or 1%
a watershed (or drainage basin) is: (2) bounded by... an area that...
1. a drainage divide 2. drains into a specific river
secondary effects of a tsunami include: (3)
1. a potential for water pollution 2. fires in urban areas 3. disease to people surviving the event
what are three ways you can melt a rock to make magma?
1. adding heat to increase the rock's temperature 2. adding water to lower the rock's melting temperature 3. decreasing the pressure on a rock
3 ways to melt the asthenosphere are by
1. decompression (decrease in pressure) 2. addition of volatiles 3. addition of heat
what are the signs that provide evidence that a volcanic eruption is about to happen (4)
1. earthquakes, especially swarms of earthquakes under the volcano, that change in depth and become shallower 2. changes in the tilt or shape of the ground on the flank of a volcano 3. an increase in the concentration of volcanic gases near the Earth's surface 4. an increase in ground temperature near a volcano
volcanoes provide (5)
1. fertile soils 2. a source of power 3. mineral resources 4. recreational opportunities 5. newly created land
the best adjustments to the flood hazard include (3)
1. flood insurance 2. flood proofing 3. floodplain regulation
in which two environments are shield volcanoes found?
1. hotspots in the ocean 2. divergent plate boundaries
primary effects of volcanic activity include (3)
1. lava flows 2. pyroclastic hazards 3. (occasionally) the emission of poisonous gases
natural service function of tsunamis (2)
1. provides a large volume of sediment that contributes to the general development of the landscape 2. they can also move nutrients inland with long-term ecosystem benefits -- the movement of seawater on land brings many chemicals from the ocean which may have long-term effects on ecosystems that may be deprived of nutrients
what issues might make wetlands redevelopment problematic? (3)
1. re-developing wetlands requires that people change how they're using their land 2. wetlands along the same river can be controlled by different state or national governments 3. species that help sustain healthy wetlands may no longer be able to live in seriously eroded or polluted land
what forms a floodplain? (2)
1. sediment deposited by lateral migration of meanders in a stream 2. the periodic overflow of the stream banks during a flood
tsunami effects are tightly linked to the earthquakes that cause them, thus, their effects are often combined with: (3)
1. the ground shaking 2. fires 3. subsidence (gradual caving/sinking of an area of land) associated with the earthquakes
secondary effects of floods include (4)
1. water pollution 2. disease 3. displacement of people 4. fire
what region has the LEAST risk from tsunamis?
Atlantic coast of the US
which of the following signs should NOT cause a person to leave a coastal area due to the threat of a tsunami?
Change in wind direction, from blowing offshore to blowing onshore
which of the following describes the tsunami in Japan in 2011?
M 9 earthquake triggered a 10 m tsunami (up to 40 m high in certain locations), which caused the meltdown of 3 nuclear reactors and killed more than 20,000 people in a country that has many high seawalls that were built to protect it from tsunamis
which of the following best describes the tsunami in Indonesia in 2004?
M 9 earthquake triggered a 10 m tsunami, which was the deadliest tsunami ever, killing more than 200,000 people in several countries
does human activity affect the wave amplitude of an oncoming tsunami?
No, human activity does not increase or decrease the amplitude
regions of N. America at risk from volcanoes include:
Northwestern coast of Cali., western coasts of Oregon and Washington, and parts of British Columbia and Alaska, Long Valley and the Yellowstone National Park area
discharge equation
Q = VA V: water velocity A: width x stage
2/3's of the world's volcanoes are associated with the sinking of lithospheric plates along the
Ring of Fire surrounding most of the Pacific Ocean
what would the longitudinal profile of a river flowing from a gentle valley into an ocean look like?
a gently downward sloping line
a tsunami refers to
a large, fast, earthquake-generated water wave
tsunamis come in
a series of waves -the second or third wave may be even larger than the first wave
which of the following describes the tsunami at Krakatoa in 1883?
a volcanic explosion caused part of the volcano to collapse into the ocean, producing a 35 m tsunami that killed 36,000 people
of the ways mantle rock can melt to form magma, what is most commonly found at hotspots?
adding heat to increase the rock's temperature
what process produces the andesitic/rhyolitic magma seen at subduction zone volcanoes?
addition of water and volatiles to the hot rock of the mantle
how are fires started after a tsunami?
after gas lines break and catch on fire
what magma will explode when it reaches the Earth's surface
an andesitic magma with gas
where would you expect the least amount of flooding due to a rainstorm?
an area that consists of forest, grasslands, and no human development
what process is responsible for all the basaltic magma at the ridges?
decrease in pressure on the hot rock of the mantle as it upwells toward a gap in the Earth's surface
channelization has often caused environmental...
degradation ex: increased water temps, no shading, no cover for fish life, reduced leaf material input, etc.
structural control is a strategy to mitigate the effects of a tsunami by
designing buildings near the shoreline with the goal of improving their ability to withstand tsunami damage
loss of life from flooding is relatively low in
developed countries where adequate monitoring and warning systems are established
when seafloor earthquakes occur, what may be produced?
distant and local tsunamis
what is the difference between a distant tsunami and local tsunami?
distant tsunamis move farther from their source before they hit land
floodplain regulation is critical because
engineered structures tend to encourage further development of floodplains by producing a false sense of security
what are volatiles?
gases trapped in magma
the major source of large damaging tsunamis has been: these tsunamis have formed where:
giant earthquakes associated with the major subduction zones on Earth geologic faulting ruptures the seafloor and displaces the overlying water
what is the difference between magma and lava?
magma is found below the Earth's surface, lava is found on the Earth's surface
lava is...
magma that has been extruded from a volcano
what is NOT a benefit of volcanoes to the Earth and its inhabitants?
many of the world's major oil fields are in volcanic rock
why are so many volcanoes found on the Ring of Fire around the margin of the Pacific Ocean?
many subduction zones occur there
if levees are built along a river to protect a town such as St. Louis, then...
narrowing in the width of the channel between the levees can cause the floodwater to back up, and increase the level of flooding upstream
in which "reservoir" of the Earth's hydrological cycle is most of the world's water?
oceans
in a meandering stream, water velocity is fastest where?
on the outside of a bend
effects of a tsunami are both:
primary and secondary
which of the following is NOT a way to minimize the hazard from tsunamis?
prohibit hydraulic fracturing for natural gas
what volcanic hazard is responsible for the greatest number of deaths?
pyroclastic flows
what volcanic hazard is responsible for the most deaths
pyroclastic flows
what is not an example of a base level for a river
rapids
sufficient monitoring of seismic activity, and changes in the land surface, combined with knowledge of the recent geologic history of volcanoes may eventually result in
reliable forecasting of volcanic activity
which magma would have the highest silica content?
rhyolitic
define "discharge" __________ times ____________
river cross-sectional area times river velocity
define "stage"
river height
what physiographic features are associated with the highest level of hazard from lahars?
river valleys
which rivers have the highest gradient?
rivers near their headwaters
what component of the hillslope hydrological cycle, if reduced, can help reduce flooding?
surface runoff
what load would make a river appear murky or dirty
suspended load
in which cycle do rivers NOT play an important role
tectonic cycle
channel pattern
the configuration (arrangement in a particular form) of the stream channel
why don't earthquakes on transform faults trigger tsunamis?
the earthquakes don't vertically displace the water in the ocean