GLY - 1030 Test 2, FAT STUDY GUIDE
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
