GLY - 1030 Test 2, FAT STUDY GUIDE

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A well-formed conical volcano located above an active subduction zone that has not erupted in 12,000 years is __________.

dormant, likely to erupt in future

When a number of earthquakes along in the same general area over the course of a few months or years, the event is referred to as a(n) __________ .

earthquake cluster

Earthquake epicenters east of the Rocky Mountains are in random locations and do not cluster in certain areas.

false

At oceanic spreading centers, magmas are rhyolitic in composition.

false, basaltic

The higher the viscosity of magma, the more fluid is its behavior.

false, lower viscosity = more fluid

The ongoing collision between Asia and the subcontinent of India is resulting in __________.

great earthquakes over a gigantic area

In San Francisco's Marina district in 1989, some fill underwent permanent deformation and settling, and some formed slurries as underground water and loose sediment flowed like a fluid in a process known as _

liquefaction

three types of folds

monocline, anticline, syncline

creep (aseismic slip)

movement along faults occurs gradually and relatively slowly and smoothly; fault displacement without significant earthquake activity

The dominant type of faulting in the Great Basin region is ______________.

normal faulting

confining stress

object is pushed down by the weight of all the material above it; since it cannot move, it cannot deform

fold

occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation if more stress is applied the rocks can fracture or undergo more folding

syncline

opposite of a fold that bends downward

Most Icelandic eruptions are __________.

peaceful fissure explosions

faults

planar breaks in rock; there is displacement of one side relative to the other

Order the following volcano types from most explosive at the top to least explosive (most peaceful) at the bottom.

plinian,vulcanian,strombolian, hawaain, icelandic P-V-S-H-I

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

pyroclastic flows

earthquake

represent a release of built-up stress in the lithosphere

difference between a reverse fault and a thrust fault

reverse fault has a steeper dip- more than 30°

felsic magma (volcano type etc.)

rhyolite or andesite volcanic glass -light color - low iron content/ high silicon content - viscous - violent eruptions (distinctive) - violent explosions - produces lava, cinders & ash, steam - mainly produces cinders & ash - large volcano - steep sided composite cone (stratovolcano) - lava dome (lava like toothpaste) - continental crust - process of caldera formation - violent explosion and collapse

The New Madrid earthquakes are apparently related to an old buried ____________.

rift zone

elastic rebound

rocks snap back elastically to their previous dimensions after the sudden displacement and associated stress release

tension (stress)

rocks that are pulled apart under tension and can lengthen or break apart; major type of stress at divergent plate boundaries

where reverse and thrust faults form

sections of the crust undergoing compression; CONVERGENT PLATE BOUNDARIES are zones of major reverse and thrust faults

The seismic-gap method of earthquake forecasting works by identifying __________.

segments along a fault that not moved for the longest amount of time

mesosphere

"middle sphere"; solid again due to high pressure

lithosphere

"rock sphere" made up of relatively cold, brittle, solid rock and is broken into Earth's plates; outermost layer

asthenosphere

"weak sphere"; zone of heat softened rock that acts like a grease layer for the plates

Human activities worsening erosion

- former farmlands turning into desserts - mining causing erosion - Agriculture - Lumbering - recreational vehicles

explosive eruptions are how much more powerful than an atomic bomb

10,000 times

year Mount St. Helens erupted

1980

high speeds of tephra

450 mph (700km/h)

# of earthquakes large enough to be noticed annually vs # causing significant damage

50,000 and 100

earthquake in China's Sichuan

7.9 magnitude; 80,000 fatalities; result of a collection of 320 million tons of water over a well-known fault line

Laterite

A red, highly leached soil type developed in tropical climates with high temp and heavy rainfall and also rich in oxides of iron and aluminum.

Lithosphere

A rigid layer made up of the uppermost part of the mantle and the crust. 75-125 km deep

Richter scale

A scale that rates an earthquake's magnitude based on the size of its seismic waves. Each step up is a 10-fold increase in wave height and a 30-fold increase in amount of energy released.

P waves

A type of seismic wave that compresses and expands the ground.

S waves

A type of seismic wave that moves the ground up and down or side to side

A horizon (topsoil)

Frequently the top layer of soil, characterized by mixing of organic material and mineral material

What affects level of violence of an eruption?

Gas content- the more gas in magma the more explosive the gas expands Viscosity of magma- thickness of magma

Soil loss in the U.S

Georgia, 4.5 tons per acre.

Terracing of slopes

Good for catching water and slowing it down. (Machu Pichu)

Mitigation

Limiting the effect

fastest and first detected waves of an earthquake

P-waves

which wave type is faster- S-waves or P-waves?

P-waves

Two broad types of soils:

Pedalfer- Aluminum and Iron in soils of the Eastern states. Pedocal- Calcium in the soils of the Western states.

Biological weathering

Physical or chemical weathering caused by plants or animals. Ex. A tree growing into a rock

Epicenter

Point on Earth's surface directly above an earthquake's focus

most common magnitude scale for earthquakes

Richter magnitude scale

ocean-continent

Rising magma can form continental volcanic arcs (Andes Mountains)

shear waves

S-waves; material is moved by flexing or deforming in a sideways fashion

Where desertification is a problem today?

Sahara desert and sahel region Africa

what earthquakes result from

a sudden release of energy in the lithosphere that creates seismic waves

outer core

completely molten, S-waves cannot travel through it & instead they create a shadow zone

composite volcanoes

composed of felsic and intermediate rock; steep slopes; constructed layer by layer; dome shape; violent & explosive

composite volcano construction

constructed layer by layer from lava and ash solidifying upon the other

reason why explosive eruptions occur

cooler, more viscous magmas reach the surface; dissolved gases cannot escape as easily, so pressure may build up until gas explosions blast rock and lava fragments into the air.

Sulfur mixing with water

creates sulfuric acid, explosive

active volcano

currently erupting or showing signs

Humus

dark organic matter that forms in soil when a dead plant or animal decays.

rock melts by

decrease pressure, increase temp, adding water

travel time for seismic waves is affected by...

density of rock

seismograph

detects ground movement and can be Records arrival of different seismic waves

right-lateral strike slip fault

dextral

effects on humans from continued exposure to hydrogen sulfide gas

dizziness, headaches, and more

composite volcano shape

dome

impact of large explosions on the atmosphere

drop in surface temperatures & depletion of the ozone layer

1815 Tambora "Year without a summer"

due to effect from an earthquake, global cooling effects.

volcanic history

encompasses the last eruption and time span between their previous ones

point that suffers the most damage from an earthquake

epicenter

Rill erosion

erosion by running water in small channels on the side of a slope. 25 cm or less

super volcanoes

extremely rare; result of a very large magma chamber; create a caldera; change life on earth- reduce sunlight; likely caused mass extinctions

Spreading ridges produce the largest number of great earthquakes.

false

The biggest disasters occur when great earthquakes occur at great depths.

false

The primary cause of deaths in earthquakes in modern times is people being swallowed alive by the ground, rather than by building collapse.

false

composite volcano composition

felsic and intermediate rock (intermediate between felsic and mafic composition)

type of magma that erupts explosively

felsic magma

Wind fences

fences that help wind speeds slow down.

Loam

fertile soil composed of sand, silt, and clay, also containing humus.

predicting volcanic eruptions: gas emissions

gas emissions are monitored because typically this occurs prior to an eruption; sulfur dioxide, carbon dioxide, water vapor, hydrochloric acid gases are monitored

Several geologic phenomena are being studied as signs of an impending volcanic eruption. These include seismic waves, ______________, and the release of gases.

ground deformation

predicting volcanoes

ground deformation,seismic waves, gas measurements

Dust Bowl of the 1930s

heavy winds carried top soil away, buried homes, and destroyed harvests. Over a million farmers were driven off their land in Western Oklahoma.

felsic magma

high in silica and contain quartz and feldspar (silicate material); more viscous than mafic magma; deeper in crust so it will cool and form igneous rock (ex: granite); gas can get stuck in the magma and build up pressure

Rhyolitic

high silica composition, high viscosity, high gas content (high viscosity)

basis for volcanic predictions

history, earthquakes, slope deformation, and gas emissions

angle of inclination of the dip of a fault plane is measured in respect to

horizontal

compressibility

how steadily the material is like to compress; more compressible relates to faster waves

origin of an earthquake

hypocenter

extinct volcano

inactive and will probably never erupt again

dormant volcano

inactive but has erupted recently

subduction zone fault

inclined fault, inclined faulting

Constraining bends in large strike-slip faults commonly "lock up"; thus, movements there tend to be __________.

infrequent and large

function of distance to the epicenter

interval of time between first arrivals of P-waves and S-waves

Chemical Weathering

involves the breakdown of minerals by chemical reaction with water, with other chemicals dissolved in water, or with gases in the air. Chemical changes the composition.

Mercalli Intensity Scale

is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake.

Flood basalts

is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava Ex. Deccan Plateau, India (64 million years ago) Siberian flood basalts (250 million years ago) Breakup of continents (Pangea) (Extinction)

explosive eruptions

large and can cause severe devastation; the result of built up pressure of gases, for when the magma breaks the seal it creates an enormous explosion of tephra

L waves (surface waves)

last wave to arrive, slowest, up and down motion, causes the most damage

Regolith

layer of loose, ground-up rock on the lunar surface.

minimum tillage or no-till agriculture

limits the amount that we disturb the soil.

Leaching

loss of soluble substances is washed off the top layer of soil by rain. They are then redeposited at a lower level.

presence of water

lowers melting point

core

made of metal, specifically Fe & Ni; density of 10-13 g/cm^3 & a thickness of ~22,000 mi.

mantle

made of ultramafic rock, has a density of 4.5 g/cm^3 & thickness of ~ 1800 mi.

magma type in effusive eruptions

mafic

shield volcano composititon

mafic basaltic lavas flow relatively easily when erupted

shield volcanoes

mafic basaltic lavas flow relatively easily; broad and gently sloping; flat and low in comparison to diameter

igneous rocks include

mafic magma and felsic magma

magma in effusive eruptions

mafic magma pushes towards the lithosphere surface through FISSURES and erupts through a vent

predicting volcanic eruptions: earthquakes

magma movement causes the ground to shake and the size & number earthquakes to increase prior to eruption; earthquakes are heavily monitored to help determine if a volcano might erupt

tephra(?) composition

magma, rock, ash

human action that has induced the greatest number of earthquakes worldwide

mining- because moving Earth's material can result in instability of the area surrounding and cause collapses that can trigger seismic activities.

violence of cinder cone volcano eruptions

minor explosive volcano

cinder cone volcanoes

minor explosive volcano; most common volcano; smaller than composite volcanoes w/ steep sides; batches of lava shot in air as pyroclastic; pyroclastic fall close to vent and create cone shape; often located near larger volcanoes

icelandic

most peaceful eruptions

Earthquakes in Hawaii are mostly related to ________________.

movement of volcanic magma beneath the ground

thrust fault

near - horizontal fault, horizontal faulting. occurs as a result of compression in; continental collision zones, and inside plates near subduction zones and curved transform faults.

normal fault

near - vertical fault, vertical faulting. occurs on top of oceanic ridges and on rifting continents above them. results from stretching of crust

mafic magma

not viscous- flows readily to the surface; low in silica and have a higher concentration of magnesium and iron rich minerals and are darker in color

Tundra soil

nutrient poor, thin soil, cold and dry air

shadow zone

An area on Earth's surface where no direct seismic waves from a particular earthquake can be detected.

liquefaction

occurs when water-saturated, unconsolidated sediments, usually silt or sand, become fluid-like from shaking. The shaking breaks the cohesion between grains of sediment, creating a slurry of particles suspended in water. Buildings settle or tilt in the liquified sediment, which looks like quicksand in movies.

crust

oceanic crust is made of basaltic rock, has a density of 3.0 g/cm^3 and thickness of ~5 mi. continental crust us made of granite rock, has a density of 2.7 g/cm^3 and thickness of ~30 mi.

caldera

often created by super volcanoes, a large volcanic crater

common location of cinder cone volcanoes

often located near larger volcanoes

mediums through which S-waves travel

only through solids

hypocenter

origin of an earthquake; point on the fault where the fracture originates at; position where the energy that is stored is being first released

Earth's interior

outer/inner core, mantle, crust

C horizon

partially altered parent material

Contour plowing

plowing along the contours of the land in order to minimize soil erosion.

P wave

primary waves- COMPRESSION waves (much quicker); body wave

reason why cinder cone volcanoes are cone-shaped

pyroclastic fall close to the vent creating a cone-shaped volcano

Gully erosion

removal of layers of soil along drainage lines creating channels.

what the speed of P-waves is determined by

rigidity: more rigid = faster the wave travels compressibility: more compressible = faster waves density: more dense = slower waves

what the speed of S-waves is determined by

rigidity: more rigid = faster the wave travels density: more dense = slower waves

compression waves- ways in which material (rocks) compress

same direction that the wave is traveling

S wave

secondary waves- SHEAR waves but pass only through solid rock (not magma)

tsunami

seismic sea waves; when an undersea or near-shore earthquake occurs, sudden movement of the sea floor may set up waves traveling away from that spot, like ripples in a pond caused by a dropped pebble

earthquake intensity of IV

shaking: light description: Felt indoors by many, outdoors by a few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

earthquake intensity of V

shaking: moderate description: Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clock may stop.

earthquake intensity of I

shaking: not felt description: Not felt except by a few under especially favorable conditions

Three basic classes of collisions include all but which of the following?

Continental plate versus mantle plate

3 different types of boundaries

Convergent- plates coming together Divergent- plates moving away Transform- plates moving sideways

earthquake intensity of VIII

shaking: severe description: Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.

earthquake intensity of VI

shaking: strong description: Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

earthquake intensity of VII

shaking: very strong description: Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

earthquake intensity of IX

shaking: violent description: Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

earthquake intensity of II

shaking: weak description: Felt by only a few persons at rest, especially on upper floors of buildings

earthquake intensity of III

shaking: weak description: Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people don't recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated

Tsunamis

shockwave on the bottom of the sea floor.

left-lateral strike slip fault

sinistral

shape and size of cinder cone volcanoes

smaller than composite volcanoes and have steep sides

release of volcanic gas into the atmosphere

soil, volcanic vents, etc.

inner core

solid again due to high pressure

mediums through which P-waves travel

solids, liquids, gases

compression (stress)

squeezes rocks together, causing rocks to fold or fracture (break); most common at convergent plate boundaries

composite volcano slope

steep slopes as the result of viscous lava not being able to travel far before solidifying

what is determined by the chemical composition (volcanoes)

style of eruption, type of volcanic cone, composition of rocks formed

What is the cause of volcanism at Italy's Vesuvius, Stromboli, Vulcano, and Etna?

subduction of Mediterranean plate beneath europe

volcanic gases that pose the greatest potential hazard (ppl, animals, agriculture, property)

sulfur dioxide, carbon dioxide, hydrogen fluoride

gases monitored to predict volcanic eruptions

sulfur dioxide, carbon dioxide, water vapor, hydrochloric acid gases

transform fault

tectonic plates sliding past one another (ex. San Andreas fault).

density

the amount of mass per volume; the more dense the material, the slower the waves

how super volcanoes change life on earth

the ash can block sunlight, reducing photosynthesis and dropping global temperatures

fault strike

the direction of the line of intersection between the fault plane and the surface of the Earth

normal fault

the hanging wall has moved down relative to the footwall

reverse/thrust fault

the hanging wall has moved up relative to the footwall

silica and viscosity

the larger the concentration of silicate, the more viscous (resistant to flow) the lava is

Moment magnitude (Mw)

the most accurate measure of a large and distant earthquake's intensity and energy release; the scale most used by seismologists in reporting worldwide earthquakes.

Mechanical Weathering

the physical breakup of rocks without changes in the rocks composition.

Sheet erosion

the process by which water flows over a layer of soil and removes the topsoil

Seismogram

the record of an earthquake's seismic waves produced by a seismograph

fracture

the rock breaks

elastic deformation

the rock returns to its original shape when the stress is removed

Athenosphere

the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

O horizon

the uppermost horizon of soil. It is primarily made up of organic material, including waste from organisms, the bodies of decomposing organisms, and live organisms.

Soil erosion

the wearing away and removal of rock and soil particles from exposed surfaces by the two major agents; wind and water.

79 AD — eruption of Vesuvius

towns of Pompeii and Herculaneum

where strike-slip faults form

transform faults

surface wave

travels along the surface; larger ground displacement than body waves; results in more earthquake damage

body wave

travels through the interior of the earth

Orogenic belt

Felsic magma Violent eruption Strong shallow-deep quake

Colliding continents

Felsic magma Violent eruption Strong shallow-med quake

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

true

Magma at great depth does not contain gas bubbles because the high pressure at depth keeps gas dissolved in solution.

truth

Divergent Margins

two plates move away from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below

location of the majority of magma

upper mantle (depth 50-250 km); bc temp is high enough and pressure is low enough to melt rocks

shield volcano shape

very flat and low in comparison to its diameter and has a large coverage

Super Eruptions

very rare, massive volcanic eruptions that eject so much dust into the atmosphere it causes extreme cooling around the globe. Ex. Toba- created Lake Toba, one of the greatest volcanic eruptions 74 million years ago

violence of composite volcanoes

violent and explosive

three v's

viscosity, volatiles, and volume

Lahar

volcanic mudflow

Which state listed below is most likely to have a magnitude 9 or larger earthquake in the next several hundred years?

washington

Liquefaction occurs when seismic waves cause __________.

water to be injected into sediment causing the grains to lose cohesion and behave like a fluid

in magma _____ is the highest dissolved gas

water vapor

seismic waves

waves of energy

shear (stress)

when forces are parallel but moving in opposite directions, the stress; most common stress at transform plate boundaries

fault

when rocks on either side of a fracture move; sudden movement along the fault can cause rocks to slip and break, and this release of energy causes earthquakes

ocean-ocean

which boundary forms islands, archipelagos and no volcanoes. Ex. Japan, Indonesia

A shield volcano has a great ___________.

width compared to height

Convergent Margins

areas on Earth where two or more lithospheric plates collide.

super volcanoes and extinction

assumed that super volcanic eruption caused some mass extinctions

Carbonate

based on carbon and oxygen. (limestone) Breaks down by humidity and rainfall.

Silicate

based on silicon and oxygen. (Quartz) Breaks down by hydrolysis.

pyroclastic in cinder cone volcanoes

batches of lava shot into the air as pyroclastic; sizes of pyroclastic range from ash (very fine) cinders, bombs, or blocks (very coarse); pyroclastic fall close to the vent creating a cone-shaped volcano

reason why super volcanoes are extremely rare

because they are of such high magnitudes

D horizon

bedrock

Freeze-thaw

breaks down rock when water gets into rock joints or cracks and then freezes and expands, breaking the rock

shield volcano slope

broad and gently sloping

predicting volcanic eruptions

can be difficult and unreliable

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

fire (earthquakes)

caused by broken gas lines and infrastructures

Island volcanic arc

chain of volcanic islands

Fluorosis

changes in acid content in soil making farm land not farmable. Ex. 1783 Iceland live stock died, 1/4 of people died

Pyroclastic debris is __________.

chucks of magma and rocks blown into the air by gas in a volcanic eruption

most common volcano

cinder cone

secondary effects of volcanic activity

climate and atmospheric chemistry

example of shield volcano

Hawaiian Islands

continent-continent

Himalayas, alps

Basaltic

Igneous rock composed mostly of dark colored, dense, minerals containing compounds of iron and magnesium. (Low viscosity)

Armero- Nevado del Ruiz

In 1985, became active with fumaroles. Killed 25,000 people

Lake Nyos and Lake Monoun

In Cameroon Africa CO2 built up in bottom, released and killed villages

Spreading ridge

Mafic magma Quiet eruption Moderate, shallow quake

Krakatau 1883

Massive volcanic eruption that caused a tsunami.

example of composite volcano

Mount St. Helens

Silting of rivers

Sediment is piling up in rivers, causing them to dry up.

transported soil

Soil that has been moved away from its parent material by water, wind, or a glacier.

residual soil

Soil that remains above its parent rock

Expansive soils

Soils that tend to increase or decrease in volume with water content. Problems- Breaks up foundation Location- Gulf Coast Potential Solutions- wet the clay, treat it with chemicals.

pyroclastic flow

The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption. Fast moving cloud of ash and dust.

zone of accumulation

The part of a glacial system where snow and ice are accumulating faster than they are melting away.

Focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake

Crop rotation

The practice of rotating use of different fields from crop to crop each year, to avoid exhausting the soil.

Liquefaction

The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud

Reforestation

The restoration (replanting) of a forest that had been reduced by fire or cutting

precursor events

With respect to natural hazards, refers to physical, chemical, or biological events that occur before an event such as a flood, earthquake, or volcanic eruption

Seismograph

a device that writes down (records) the movements of the earth Ex. During an earthquake

Wind breaks

a line of tree's help break the wind.

volcanoes

a location which allows molten rock and gas to escape from a magma chamber

rigidity

a material's strength to resist being bent; more rigid = faster the wave travels

caliche

a mineral deposit of gravel, sand, and nitrates, found especially in dry areas of South America. Calcite deposit. (Limestone)

Permafrost

a permanently frozen layer of soil beneath the surface of the ground. Problems- road damage Solutions-

B horizon

a soil horizon; B receives the minerals and organic materials that are leached out of the A horizon.

effusive eruptions

a type of eruption in which lava steadily flows; gentler lava flow in comparison to explosive; form lava flows and lava domes; MAFIC magma

effusive eruption

a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground

super volcanoes are the result of...

a very large magma chamber and erupts in one catastrophic eruption

lahars

a volcanic ash and water mudflow

predicting volcanic eruptions: slope deformation

a volcano's slope can be deformed because of magma and gas build up; it can be subtle, and measured by a tiltmeter; ground swelling can occur and can result in rock faults and landslides (occurred prior to Mt. St. Helens eruption)

result of sulfur dioxide

acid rain and air pollution

where earthquakes occur

along faults

Seismic gaps

an area along a fault where relatively few earthquakes have occurred recently but where strong earthquakes have occurred in the past

explosive eruption

an eruption that is thick and sticky, has a high gas content and is high in silica. High viscosity leads to a buildup of gases because of gas bubbles having a hard time from escaping the magma it builds a bigger pressure.

What was the origin of the gas that killed 1,700 people in Cameroon in 1996?

It leaked upward from basaltic magma underlying a lake.

Several recent earthquakes in Washington's Puget Sound region were caused by movement of the subducting ______________ Plate.

Juan de Fuca

Mantle hot spot

Magic magma Quiet eruption Mild shallow quake

In 1985, __________ produced a minor eruption that melted part of a glacier near its summit, sending a lahar down its slopes and killing at least 22,000 people.

Nevado Del Ruiz, Colombia,

Subduction trench

No magma No eruption Strong shallow quake

Transform fault

No magma No eruption Strong shallow quake

Spreading centers have relatively peaceful eruptions of magma because the __________.

SiO2-poor magma is at high temperatures.

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

Vulcanian-type

In the 1989 Loma Prieta quake, the Marina District building collapses were extensive, and numerous destructive fires broke out, due to all but which one of the following?

Widespread looting and arson

stratvolcanoes

__________ 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.

Plinian

__________ eruptions are the most violent types of explosive eruptions.

decompression`

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

strike-slip fault

a dip-slip fault in which the dip of the fault plane is horizontal

anticline

a fold that arches upward and the rocks around surrounding it dip away from the center of the fold; CENTER rocks signify the oldest rocks with the newest rocks laying on top

epicenter

actual point on the earth's surface directly above the focus

Which of the following can help make rocks melt beneath Earth's surface?

adding volatiles, increasing temp, decreasing pressure

A caldera collapse occurs ________________.

after magma chamber almost empty

The typical trend in a rising plume of subduction-zone magma is to increase the ____________.

all of the above

focus

also called hypocenter; actual site of the first movement along a fault

Which of the following states has the highest earthquake risk?

arkansas

mafic magma (volcano type etc

basalt - dark color - high iron content/ low silicon content - low viscosity - quiet explosions/ fountaining - from central vent gradual - large volcano - shield volcano/ flat volcano/ lava plateau - small volcano - cinder cone + flat lava flow - oceanic crust - process of caldera formation - collapse of the summit after being undermined by a flank eruption

Seafloor spreading generates __________ magma

basaltic

Rank the following plate tectonic boundaries from most explosive volcanic activity to least explosive volcanic activity.

subduction,spreading, transform

plastic deformation

the rock does not return to its original shape when the stress is removed (reshaping the rock)

hanging wall

the rocks above a fault; the upper or overlaying block along the fault plane

footwall

the rocks beneath a fault

Active volcanoes today in Oregon and Washington, including Mt. St. Helens, result from _________________.

the subduction of the Juan de Fuca Plate beneath North America

The basaltic magmas that erupt on the ocean floor have a low SiO2 content, high temperature, and allow gas to escape easily, all resulting in non-explosive eruptions.

true

The eruption of Nevado del Ruiz in Columbia in 1985 dropped hot pyroclastic debris onto glaciers, resulting in lahars.

true

monocline

type of fold- a simple bend in the rock layers so that they are horizontal; a STEP-LIKE in rock strata consisting of a zone of steeper dip with an otherwise horizontal or gently-dipping sequence

transform fault

vertical fault, horizontal faulting. occurs between sections of oceanic ridges

The greatest earthquakes in the world occur _____________.

where plates collide with each other


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