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