natural disasters test 2 chap 5-7

what are the three signs of an impending volcanic eruption

1. increased earthquake activity, as seismic waves are created as magma rises 2. swelling and sinking of the surface as magma moves up or withdraws 3. gas measurements of CO2 and SO2 as increasing SO2 means imminent eruption

our ability to forecast earthquakes on a _________ term timescale is fairly good, but we have no ability to predict earthquakes on a ______ term timescale

1. long 2. short

at what approximate depth is magma generated below subduction zones

100 km

volcanologists estimated that about _________ people have died by volcanic activity in the past 500 years

275,000

The number of states in the U.S. that have experienced a measurable earthquake is

50

more than 98% of the earth's crust is made up of only ___ elements

8

Over _________ of Earth's magma extruded through volcanism takes place at the oceanic spreading centers.

80%

two states where the majority of earthquake activity occurs

Alaska and california

a number of large cities lie within the new madrid seismic zone, including

St. Louis, Memphis, Nashville

Which of the following represents evidence for major fault movement on the Seattle Fault zone about 1,100 years ago?

The former shoreline at Restoration Point was uplifted 7 meters above the high-tide line in a single event. Numerous large landslides occurred at this time, including some that carried trees in growth position to the bottom of Lake Washington. Several tsunami deposits have been recognized in the sediment layers of the area. The same date appears in the ages of six major rock avalanches in the Olympic Mountains.

Volcanic eruptions with which of the following VEIs happen the most often?

VEI of 3

vesuvius, italy

VEI- 6. last major eruption 79 CE was detailed by a 17 year old pliny the younger. the well preserves remains of pompeii and herculaneum make this one of the most famous eruptions in history. it killed over 10,000 people many of whom refused to leave and were killed in the pyroclastic flows

st helens

VEI-5. in 1980 after 123 years it erupted and is still the deadliest and most economically destructive volcanic event in the history of the US.

krakatau, indonesia

VEI-6. in 1883 a series of vulcanian eruptions was followed by a plinian eruption that created a blast heard thousands of miles away. several huge deadly tsunami were created as parts of krakatau collapsed. anak krakatau broke the surface in 1927

pinatubo, indonesia

VEI-6. in 1991, after 500 years a cataclysmic piling eruption was accompanied by heavy pyroclastic flows. typhoon yunya with its torrential rain created a tremendous lahar. this was perhaps the best forecast eruption in history

thera (santorini), greece

VEI-6. last erupted in 1628 BCE and is believed to be responsible for the dramatic collapse of the productive minoan civilization on nearby crete. it may have been responsible for the disappearance of the island empire of atlantis as well as being a natural force behind the biblical plagues against egypt during the exodus.

tambora, indonesia

VEI-7. in 1815 the most violent and explosive piling eruption in the past 200 years. and perhaps the most deadly it affected worldwide climate, devastating crops, leading to famine and disease. attributed to the year without a summer in 1816

yellowstone

VEI-8. last erupted about 640,000 BCE. it is a continental hot spot capable of catastrophic caldera eruptions every 660,000 years or so

toba, indonesia

VEI-8. last resurgent caldera eruption about 72,000 BCE. accused of creating a volcanic winter and triggering of an ice age. it is thought to have reduced an entire world human population to 10,000 or fewer people creating a bottleneck in human evolution

andesitic magma

a coposite magma with in-between characteristics of basaltic to rhyolitic

estimating the number of people who have died from volcanic eruptions is difficult because

a lack of written historical records for some time intervals and parts of the world

what best describes a stratovolcano

a large volcano composed of alternating layers of pyroclastic fragments and solidified lava flows

what criteria does the USGS define as a significant earthquake

a magnitude 6.5 or greater or an earthquake that causes death or considerable damage

a failed rift can occur when

a rift fails to open up enough to form a spreading center

a scarp is

a steep slope created by the movements of faults

why would a new madrid earthquake today be more devastating than 1811-1812

a very large area will be subject to the shaking and that area is heaily populated. most of the buildings are not earthquake proofed and the wide extent and thickness of the soft sediment foundations will amplify seismic vibrations

a ______ basalt lava flow has a rubbly and jagged surface

aa

A caldera collapse occurs

after the magma chamber is mostly empty

fault lines in the new madrid seismic zone are being mapped, thanks in part to _____________ that are still occurring 200 years after the new madrid events in 1811 and 1812

aftershocks

which US state is the most active earthquake state? least active?

alaska is the most active florida is the least active

what are the likely sources of intraplate earthquakes

ancient (failed) rift valley faults

what kind of magma is found at spreading centers? subduction zones?

basaltic magma is found at spreading centers and hot spots rhyolitic magma is found at subduction zones

The 17 January 1994 Northridge earthquake in Los Angeles was generated on a _______ thrust fault

blind

describe a caldera. what is meant by a resurgent caldera?

caldera- high viscosity, high volatiles, very large volume. these eruptions are the largest of the violent, explosive behaviors. resurgent caldera- after a giant continental caldera has gone through its eruptive sequence, magma returns causing a raised central area in the caldera

the first great shakeout event was held in ___________ to help prepare residents for the next large earthquake

california

In August 1986, a gigantic volume of __________ belched forth from Lake Nyos in Cameroon and swept down the adjacent valleys asphyxiating 1,700 people.

carbon dioxide

which gas was ultimately responsible for the deaths of thousands of villages near lake nyos

carbon dioxide

The Toba eruption 74,000 years ago may have

caused a great reduction in the worldwide human population

another name for a stratovolcano

composite volcano

__________ melting occurs when a rock melts due to a lowering of pressure.

decompression

what causes most rock to melt during the eruption sequence

decompression melting: most rock that melts to form magma is because of decreasing pressure on it, not by adding more heat

when a rupture moves along a fault, it tends to send more energy in the direction it is moving. this phenomenon is called

directivity

within a normal fault, one rock moves ______________ another

down and away from

Prehistoric earthquakes may be interpreted using faulted pond sediments. The amount of offset of sediment layers from one earthquake is proportional to the

earthquake magnitude

pillow lava

ellipsodial masses formed in water

When rock heats and liquefies into magma its volume

expands, and neighboring brittle rock must fracture and move out of the way

a _________ rift forms when the rifting process stops before separating a continent

failed

Thrust faults that do not reach the surface are called dark thrusts.

false

what kind of eruption was the 1783 lakh eruption, which produced the most lava by volume of any volcano in recorded history

fissure eruption

what is the worst case scenario for volcanic effects on climate

flood basalt volcanism, linked directly to mass extinctions

describe a flood basalt. what are these eruptions linked to in the past

flood basalt- low viscosity, low volatiles, very large volume. the largest volcanic eruptions on earth. emit tons of dcimate-modifying volatiles (CO2 and SO2) and have been linked to mass extinction

vast outpourings of basaltic lava from fissures that cover very large areas of the earth's surface are called

flood basalts

the less viscous a fluid, the more __________ it is

fluid

in what ways do lava domes present hazards?

gravity-driven landslides can be generated from the steep sloped of lava domes lava domes can plug a volcanic vent, allowing pressure to build, which leads to a violent eruption

Mt. Rainier, Washington, is number one on the danger list of many U.S. volcanologists because of its

great height, extensive glacial cap, frequent earthquakes, active hot water spring system (which have weakened the mountain internally)

The Great Basin region between the eastern Sierra Nevada in California and the Wasatch Mountains in Utah ______________________ in response to plate-tectonic forces.

has expanded in an east-west direction

distinguish between hawaiian and icelandic types

hawaiian type- usually preceded by a series of earthquakes, can erupt with "curtains of fire" (lava fountains) and rivers of very hot basaltic lava icelandic type- basaltic lava pours out in linear vents or long fractures, creating a long "curtain of fire", known as the most peaceful eruptions on earth

earthquake lake formed as a result of the ________ earthquake

hebgen lake

what caused the widespread failure of structures in the 1994 north ridge earthquake

high ground acceleration, both horizontally and vertically, caused intense shaking

pyroclastic flow

high speed, very hot, gas charged potentially deadly emission from an explosive eruption

what can change the viscosity of magma? what are volatiles?

higher temp lowers magmas viscosity. increased silica and increased amounts of mineral crystals in the magma increases its viscosity. volatiles are dissolved gases in the magma, such as H2O, CO2, SO2

what explains the peaceful nature of eruptions at spreading centers?

highly fluid magma low silica content of the magma high temperature of the magma low volatile content of the magma

primary lahars were generates during the nevado del ruiz eruption in 1985 when

hoy pyroclastic debris began melting the volcanos ice cap

The most peaceful eruptions are __________ eruptions.

icelandic type

"the big one" that everyone expects for los angeles

if the san andreas moved in a magnitude 8 at the same time as the thrust faults move in a 7, it would be as if the 1857, 1971, and 1994 earthquakes all occurred simultaneously

lake nyos

in 1986 CO2 gas bubbled out of the volcano into lake nyos and swept down the nearby valleys overwhelming four villages. nearly every living thing except plants were asphyxiated

nyiragongo, zaire

in 2002 a sudden lava flow raced down the mountain right through the city of goma. the low viscosity lava (low silica content) reached speeds of 40-60 mph.

what are three ways in which rock may melt?

increasing temperature, addition of water, lowering pressure

The viscosity of magma is lowered by

increasing temperature, decreasing crystal content, decreasing suffer dioxide content

famine is one example of how volcanoes can have an _________ effect on humans, by lowering agricultural production and killing livestock that humans depend upon for survival

indirect

basaltic magma

is of high temp, low silica (SiO2) content, low in dissolved H2O, resulting in low viscosity, associated with peaceful eruptions

rhyolitic magma

is of lower temp, higher silica content, high in dissolved H2O, resulting in high viscosity, associated with explosixe eruptions

As minerals form in magma kept at a constant temperature, what happens to the viscosity of that magma?

it increases

the 1991 mount pinatubo eruption featured massive ______ that were produced when typhoon bunya passed over the volcano, dumping heavy rainfall

lahars

when very high viscosity lava piles up over a volcanic vent, it typically forms a

lava dome

describe a lava dome and its role in a major eruption sequence

lava dome- high viscosity, low volatiles, small volume. magma cools quickly, producing a hardened dome or plug in as little as a few hours and can grow over decades. very common on top of stratovolcanoes

one of the most dangerous phases of a volcanic eruption occurs when

less energy is fed into the eruption column, causing it to collapse, and sending pyroclastic flows down the flanks of the volcano

The presence of water ________ the melting point of rock.

lowers

what is the role of water concentration in a volcanic eruption

magma with low concentrations will not be explosive, whereas magma with high concentrations can be explosive

quasi-periodic fault movement

major movements occur at approximately the same time intervals

why is volcanism not generally associated with transform faults?

mantle material is neither rising nor sinking at transform boundaries, the plates are simply sliding past each other

sector collapse

massive slope failure along the flanks of a volcano due to fracture of rotten rock

describe a stratovolcano. distinguish bewteen vulcanian and plinian types

med/high viscosity, med/high volatiles, large volume. steep-sided, symmetrical volcanic peaks. vulcanian to piling eruptions of andesitic to rhyolitic magma. has a protective cap between eruptions. the vulcanian eruption clears the throat of the volcano by alternating between ejecting lava and pyroclastic material. the plinian eruption throat is now clear have incredible vertical columns of pyroclastic debris including tons of pumice up to 30 miles into the atmosphere

the spectacular spine that formed on _________ in the caribean, prior to its deadly 1902 eruption, is an example of a lava dome

mont pelee

pyroclastic surge

more dilute, less dense, fast moving flow, larger fraction of steam

The number of active "hot spots" on Earth over the last 10 million years active is

more than 100

in eastern north america, large earthquakes

mostly occur at the sites of failed rifts, lack significant recent faulting, are associated with low-strain regions

pyroclastic flow

movement is largely controlled by topography, larger fraction of pyroclastic material can move at speeds that exceed 100 m/sec. is a mixture of magma, volcanic ash and gas, and air. can reach temp of 350 C

Earthquakes in Hawaii are mostly related to

movement of volcanic magma beneath the ground

clustered fault movement

movements occur in succession for seven years and then do not occur again for decades or centuries

A genuine success story of advance warning before a large eruption occurred in the Philippines in 1991 before the climactic eruption of

mt. pinatubo

random fault movement

no definable pattern and inherently unpredictable

name the non explosive, somewhat explosive, and explosive volcanoes

non-explosive: icelandic, hawaiian somewhat: strombolian explosive: vulcanian and plinian

The dominant type of faulting in the Great Basin region is

normal faulting

southern california experiences many earthquakes because

northward movement along the san andreas fault creates many thrust faults

earthquakes as large as magnitude 5 have been produced in Nevada as a result of the underground testing of _____________ weapons

nuclear

in addition to the presence of soft sediments, the next earthquake to strike seattle could cause extensive destruction due to the presence of

numerous bridges and unreinforced masonry buildings

the majority of earthquake hazards in the US are connected to

ongoing subduction along the west coast of north america

where is most of the volcanism on earth located

over 90% of volcanism is at the edges of tectonic plates

the release of carbon dioxide from lake nyos mirrors an earlier event at lake monoun in 1984. it is thought that this earlier event was probably due to

overturning of lake water layers during the rainy season

what are the two most abundant elements in earths crust

oxygen (45%) silicon (27%)

the two more abundant elects in the earth's crust are

oxygen and silicon

what are the two primary building blocks of knowledge for understanding volcanic eruptions

properties of magma and plate tectonics

during the 1980 mount st helens eruption, a _________ was generated by a direct blast traveling more than 150 m/sec and annihilating everything in its path

pyrocalstic flow

Dome collapse, overspilling crater rim, direct blast and eruption column collapse are all ways to generate

pyroclastic flows

why is a pyroclastic flow so deadly? what is, and what causes, a lahar?

pyroclastic flows travel at high speed over 100 mph are gas charged and super hot over 100 F and will cause instant death if caught in one. lahar- a volcanic mudflow, caused when heavy rain falls on thick piles of pyroclastic debris

fault movement timing groups fall into one of three classifications:

random, clustered, and quasi-periodic movements

the great basin region is subject to many earthquakes because of

regional extension in the basin and range province

what strange event took place in four villages near lake nyos, cameroon, on august 21, 1986

residents were asphyxiated from a gaseous cloud, causing about 1700 deaths

a new mass of rising magma that bows up the caldera floor following a caldera eruption is called a

resurgent dome

The New Madrid earthquakes are apparently related to an old buried

rift zone

more than 80% of the earthquakes in the central US occur along ancient

rifts

more than 1,000 km long and composed of interconnected, asymmetrical fault block valleys, the _____________ rift is one of the major continental rifts in the world

rio grande

aa lava

rough, blocky-looking surface

describe scoria (cinder) cones. what is a strombolian type

scoria cone- low/med viscosity, med/high volatiles, small volume. are conical hills of low height. strombolian type eruptions of basaltic to andesitic magma. can erupt from hours to several years, but once it ceases, it does not erupt again

Which of the following are being studied to help forecast volcanic eruptions?

seismic waves, ground deformation, gas measurements

annualized earthquake loses are calculated from a number of factors including

shaking potential, building types, population size

describe a shield volcano

shield volcano- low viscosity, low volatiles, large volume. basaltic lava that forms a volcano is much wider than it is tall. down for peaceful eruptions

for people living near an active volcano, what must they consider

since a volcano may be active for millions of years, but centuries may pass between individual eruptions, the time scale of an active volcano must be considered by people living nearby

a high viscosity rhyolite magma with low water content will produce a

slow moving lava flow

what best describes the appearance of the surface of a pahoehoe basalt flow

smooth and ropy

pahoehoe lava

smooth, ropy-looking surface

where are the peaceful volcanoes found? explosive?

spreading center are peaceful subduction zones are explosive and dangerous

more than 80% of earth's magma is erupted at

spreading centers

what explains why spreading centers are the ideal locations for volcanism?

spreading centers lie above the high-temp asthenosphere the upward motion for the asthenosphere below spreading centers causes a decrease in pressure

__________ are steep-sided, symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.

stratovolcanoes

what is the most active volcano on earth and where is it located

stromboli, italy

what style of eruption is typically associated with scoria cones

strombolian

although still debated, it is speculated that the 2008 sichuan earthquake was caused by ______ near the longmenshan fault

the creation of the zipping reservoir

why does short-tern earthquake prediction currently appear impossible?

the detailed behavior of fault movements appears to be too unpredictable

radiocarbon dating is useful for events that have occurred only within the past 50,000 years because

the half life of carbon-14 is short

the greatest lava eruption in the historic record is

the laki fissure event in 1783

what tectonic features are most likely reactivating these old faults

the opening of the atlantic ocean basin pushes north america to the west-southwest thereby compressin the weakness of the ancient rift valley faults, creating earthquakes

continued human development near mount shasta could prove disastrous because

the rock record shows previous eruptions of mount shasta were much larger than those of mount st. helens. several town are already located within the danger zone for pyroclastic flows. nearby towns are located in valleys, which are more susceptible to lahar flows

why is a large earthquake more destructive in the eastern US than a similar one out west

the rocks in the eastern US are older, more solid rocks which would extend the damage area, as compared to the younger, more shattered rocks our west

paleoseismology

the study of ancient rock and sediment deposits for signs of earthquakes

neotectonics

the study of tectonic activity in recent geological time

what happens to volatiles in a magma as it rises toward the surface

the volatiles come out of solution and from bubbles

a ________ fault is a type of reverse fault that is inclined at a shallow angle

thrust

the _______ eruption on the island of sumatra 74,000 years ago nearly drove humans to extinction

toba

which plate tectonic settings are not associated with volcanic activity?

transform faults, continental collision zones

In Icelandic-type eruptions, low-viscosity, low-volatile content lava erupts peacefully.

true

In historic time, Nevada has averaged one earthquake with a magnitude in the 6s per decade and one with a magnitude in the 7s every 27 years.

true

The most dangerous volcanoes tend to be in the same general plate-tectonic settings as the largest earthquakes in the world.

true

Water circulating at thousands of feet below the surface can be heated to temperatures far above 100°C (212°F) without boiling because the pressure of the overlying groundwater body is so great.

true

magma at great depths does not contain gas bubbles

true, the high pressure at depth keeps volatiles dissolved in the magma

the potential hazards of volcanic eruptions are extensive and include

tsunamis, lava flows, lahars, poison gas

what is an ultra plinian eruption

ultra plinian eruptions produce huge volumes of magma over short periods of time with extra high ash columns and widespread sheets of outward flowing ash and pumice. can catastrophically change global climate for the worse. ex: yellowstone and toba, indonesia

in 2009 a group of scientists and engineers in italy were charged with manslaughter in connection with a 6.3 M earthquake that killed 309 people in the city of L'Aquila. the group was put on trial because they

underrepresented the risk of a big earthquake, giving city residents a false sense of security

The three 'Vs' of volcanology are

viscosity- controls whether magma flows away or piles up volatiles- controls the explosively of an eruption volume- controls the intensity of an eruption

what are the three V's of volcanology

viscosity- how easily doesnthe magma flow volatiles- how much dissolved gas, does it bubble out harmlessly or blast out explosively volume- the greater the volume, the more intense the eruption

what is the VEI and what factors are included

volcanic explosivity index. includes volume of material erupted, how high the eruption reached, and how long the eruptive blast lasted. the vei ranged from 0 (peaceful) to 8 (catastrophic)

as a result of the 1783 lake fissure event in iceland,

volcanic gasses killed more than half of the country livestock. the growth of important agriculture plants was slowed. a famine killed 10,000 people.

_________ eruptions are common first phases in the eruptions of volcanoes as they "clear their throats" before emitting larger eruptions.

vulcanian type

sector collapses occur when

water forcefully expands in a volcano due to contact with magma an earthquake occurs magma injection inflates a volcano

Today, North America has several small- to medium-sized plates subducting beneath its

western margin

what are thrust faults and blind faults

when compressional forces push one rock mass up and over another in a reverse fault movement, this causes shredding and slicing creating a maze of thrust faults. when thrust faults do not reach up to the ground surface, they are called blind thrusts