Earth Science Ch. 6-9
The atmospheric pressure at sea level is approximately
1 kilobar
If pure olivine melts at 1,890°C and pure pyroxene melts at 1,390°C, and peridotite is a mixture of the two, which of the following is a likely melting temperature for peridotite
1,270° C
Figure 6.9 depicts solid Earth cut in half to show its internal structure with the thickness of the lithosphere exaggerated for clarity. How much is this exaggeration, approximately?
100X
The mantle makes up _____________ percent of Earth's volume
80
Rock deforms ___________ under small amounts of stress and returns to its original shape and size when the stress is removed
Elastically
Continental rifting occurs when two continental plates converge
False
Earthquakes at divergent plate boundaries are deeper and stronger than earthquakes that form at convergent plate boundaries
False
Magma in the asthenosphere is primarily granite
False
Nitrogen molecules released during volcanic eruptions can reflect sunlight in the upper atmosphere and cause radiational cooling on Earth's surface
False
Oceanic crust is thicker than continental crust
False
Oceanic crust subduction into the mantle is the reason Manhattan Island is now nine meters farther from London that it was in 1776.
False
Slippage at the New Madrid fault zone caused the 1906 San Francisco earthquake.
False
The Indian subcontinent was originally part of ____ 200 million years ago
Gondwana
Consider the discussion of how earthquake frequency and intensity are related as stresses build and are released along active fault zones. Which statement best describes the mechanism by which 'aftershocks' occur?
Elastic rebound of strain built up in areas adjacent to a zone ruptured during an earthquake
____ explosions occur in regions in which the groundwater has been heated past the boiling point.
Hydrothermal
The underthrusting of ____ beneath Tibet caused the rise of the Himalayas
India
Some scientists suggest that future plate motions will rearrange the current configuration of continents, and form the next supercontinent near the present-day ____________
North pole
Which of the following is the name of the first super continent?
Nuna / Columbia
The seafloor and oceanic crust at the Mid-Atlantic Ridge becomes ________ with increasing distance from the ridge axis
Older
Earth's magnetic polarity reversals are caused by the magnetic field generated within the ____.
Outer core
Sound is which type of wave?
P waves
A rock that has deformed _______ under stress keeps its new shape when the stress is released.
Plastically
How is the continental crust above a subduction zone thickened?
Plutons and volcanic rock are added
Surfing takes place on which type of waves?
Rayleigh waves
Considering that the Hudson Bay region remains depressed from the weight of continental ice sheets from the last ice age, what can be said about the nature of the isostatic rebound?
Rebound takes place over the time span of thousands of years.
Magnetic orientation in rocks that is opposite to the current orientation of Earth's magnetic field is called ________________ magnetic polarity
Reversed
The amplitude of a wave form on a seismograph with vertically oriented drum measures what, exactly?
Rise and fall of the ground in a time scale of minutes
Earth's deepest borehole is located in northern ____ and extends to a depth of 12 kilometers.
Russia
Folds, reverse faults, and thrust faults are common the Appalachian Mountains whereas strike-slip faults are common to the ________ because they formed in a transform plate boundary
San Gabriel Mountains
Why would we expect to find relatively young volcanic rocks in the Himalayas when there are no volcanoes, extinct or otherwise, to be found
Subduction of oceanic crust occurred just before the Asia and India collided.
What is the relation between earthquakes and tsunamis pertaining to the San Andreas Fault in California?
The San Andreas is a transform fault and will not produce tsunamis regardless of magnitude.
Which event would register the highest on the Mercalli scale?
The atomic bomb that was dropped on the city of Hiroshima
Why is the damage much greater for earthquakes of comparable magnitude in Haiti or Pakistan than in Japan?
The building codes in Haiti and Pakistan are not effective or enforced.
Objections to Wegner's theory of continental drift included the problem of how friction could be overcome given the sheer weight of the continents. This problem was solved decades after Wegner died with what insight?
The continents glide over a layer that deforms plastically even though only a tiny fraction of it is molten.
Why does a strike-slip fault not have a footwall
The fault plane is vertical
Zircon grains from Australian sandstone give radiometric dates of 4.4 billion years, although the sandstone was deposited more recently. What can we infer from this
The first continental crust on Earth formed 4.4 billion years ago and was granitic in nature.
Geologists use a travel-time curve to calculate the distance between the earthquake epicenter and the earthquake focus
True
In liquefaction, the soil loses its shear strength and becomes a slurry
True
It is sometimes possible to predict a large earthquake a few seconds before a building begins to shake and topple
True
Long term predictions of when earthquakes will occur are fairly accurate
True
The Mid-Oceanic Ridge is elevated above surrounding seafloor because it is made of hotter and less dense lithosphere than oceanic crust farther away from the divergent boundary
True
The deeper you go into the Earth, the greater the concentration of iron is present in the rock
True
The eruption of Mount Pinatubo in the Philippines produced such great ash and sulfur clouds that Earth's surface temperatures were cooler for the following two years
True
The seafloor spreading hypothesis was put forth after oceanographers detected changes in the magnetic polarity of newly formed oceanic crust near the Mid-Atlantic Ridge
True
A tuff that forms during an eruption by fallout of particles from the atmosphere is called a(n) ________
air-fall tuff
The physical form of a composite volcano is best described as having ________
alternate layers of flows and pyroclastics
Oceanic crust is composed primarily of
basalt
Which crustal rock type is newly forming at the East African Rift zone?
basalt
A body of intrusive igneous rock exposed across more than 100 square kilometers of Earth's surface is called a ________
batholith
The Himalayas were formed ____
by the convergence of two continental plates
A(n) ____ is a crater formed by the collapse of a magma chamber
caldera
After gas-charged magma erupts, the roof of a magma chamber can ________
collapse
Regularly spaced cracks that commonly develop in lava flows, grow downward starting from the surface, and typically form five- or six-sided columns are called ________
columnar joints
Which kind of volcanic feature indicates that a variety of magma compositions are being produced?
composite cone
Underthrusting occurs as a result of ________
continent-continent crust collision
The Indian continent would not subduct into the mantle below the Asian continent because the ________
continental crust is too buoyant
The primary process by which volcanoes influence climate change involves the ________
conversion of sulfur dioxide (SO2) to sulfuric acid (H2SO4)
The rising of the Himalayas coincided with global ________
cooling
The Mohorovicic discontinuity was identified through the passage of seismic waves between the ____ and the ____.
crust; mantle
A circular or elliptical anticline structure is called a ____
dome
Folds are categorized on the basis of their axial surface and ________
facing direction
A thrust fault is a reverse fault that is nearly vertical
false
Basaltic magma has longer chains of silicate tetrahedra than granitic magma
false
Island arcs are formed at spreading centers along the Mid-Oceanic Ridge
false
Magma forms abundantly at transform boundaries
false
The rising of the Himalayas coincided with global warming
false
Volcanic eruptions covering large geographic areas that can cause great environmental damage while not being explosive are called ________
flood basalts
A shield volcano is produced by ____
fluid basaltic magma that builds a gently sloping mountain
A sedimentary basin between a trench and an island arc is called a ____
forearc basin
The convergent down-warping of the crust can often produce a ________
foreland basin
What process prevents tectonic plates from slipping past one another
friction
A wedge-shaped block of rock that drops downward between a pair of normal faults is a(n) ____
graben
A volcano in continental crust would be expected to ________
have a granitic composition
A syncline ____
is the portion of a fold that arches/dips downward
Convergence is common in the Pacific Ocean and as such, we can expect that there is an abundance of ________ there
island arcs
The concept that suggests the asthenosphere flows laterally away from a region to make space for a heavy lithospheric mass is known as ___________
isostasy
Oceanic crust (basalt) has ________
less magnesium and iron and more silica relative to mantle rock
The collision of the Indian and Asian continents caused melting of the ________
middle crust
Rocks, such as shale, limestone, and marble, tend to deform in a(n) ____ manner
plastic
Melting caused by decreased pressure is called ____ melting
pressure-release
The downslope sliding of the lithosphere away from a spreading center is called a ________
ridge push
Earthquakes do not occur when rocks deform plastically
True
Deep-seated earthquakes are more likely to occur at which of the following?
Benioff zones
What criterion distinguishes the mantle from the crust?
Composition- The mantle is peridotite in composition.
Given that plate tectonics has been active on Earth for at least 2 billion years, which of the following statements is most likely to be true?
Continental crust is older than oceanic crust.
The entire mantle-lithosphere system circulates in great ____________ cells.
Convection
Which conclusion may be reached if a magnetic field is detected around a rocky planet or moon?
It has a metallic liquid outer core and a metallic solid inner core.
Which of the following is true about the epicenter of an earthquake?
It is the location on the surface directly above the focus where the greatest amount of energy is released during an earthquake.
Potassium feldspar and apatite (a phosphate mineral) are minerals that are endemic to granite, and no potassium- or phosphorous-bearing minerals are compatible with basaltic compositions. Given that both potassium and phosphorous are fundamentally necessary nutrients for life-as-we-know-it, which statement must be true?
Life-as-we-know-it is only sustainable on planets where tectonic cycling regenerates melts of granitic composition and resupplies the surface with potassium and phosphorous.
Given the explanation for why S waves do not travel through liquid, which of the following statement is likely to be true?
Love waves also do not travel through liquids.
The planet Mars is considered to be tectonically 'dead'. Why?
Mars lacks mantle convection.
How are the epicenters of earthquakes determined?
The interval between arrival times of P and S waves converges to a unique geographic point among three or more seismograph readings at different locations.
'Geostrophism' was the name given to the dominant explanation in Wegner's time for how continents and oceans formed. 'Geostrophism' suggested that continents did not drift, but that ocean basins and continent highlands were downward and upward movements of a single continuous but dynamic crust. In this way, mountains became oceans and oceans became mountains. Which piece of evidence used by Wegner for continental drift is incompatible with the idea of 'geostrophism'?
The lateral drift of continents
What happens when a new mountain range is eroded with water and ice?
The mountains isostatically adjust upward.
Assume that oceanic crust is of uniform basaltic composition. What factor, if any, determines which plate will subduct where two plates carrying oceanic crust converge?
The older plate will subduct
If an avocado can be used as a model for the internal structure of the Earth, what part of that internal structure cannot represented by the avocado?
The outer core
What part of an analog (i.e., not digital) seismograph stays stationary during an earthquake?
The weighted pen
Assuming that the rate of spreading away from a spreading center is consistent globally, where in the world would you expect to find the oldest oceanic crust?
The western Pacific, north of Papua, New Guinea
Assuming that the rate of spreading away from a spreading center is consistent globally, where in the world would you expect to find the thickest oceanic crust?
The western Pacific, north of Papua, New Guinea
Where are large and deep-seated earthquakes most common in the world?
They are concentrated around subduction zones such as around the Pacific and the Indonesian island of Sumatra.
Hot spots migrate on the surface of the crust over time. Why?
They are linked to deep mantle plumes that are decoupled from lithospheric plate movements.
Rocks will deform depending on composition, temperature, pressure, and ________
Time
A tsunami, produced by an undersea earthquake, may travel at 750 kilometers per hour
True
Continental crust does not normally sink into the mantle because continental crust is of lower density than mantle material.
True
Partial melting is the process in which a ________
silicate rock only partly melts and forms magma that is more silica rich than the original rock.
Water typically escapes from granite magmas as they rise through the crust. A fortunate result of this hot water loss into the surrounding rock is that we find ________ .
sinter deposits
Basaltic magma commonly remains liquid and rises to the surface to erupt from a volcano or flow onto the seafloor at the Mid-Oceanic Ridge. In contrast, granitic magma usually ________ .
solidifies within the crust
Magma with a high water content has a greater tendency to ____ in the crust as compared with magma with a lower water content
solidify
Nearly all of Earth's oceanic crust is created by ____
spreading centers
Mount Vesuvius is an example of a ____ volcano that is a steep-sided volcano formed by an alternating series of lava flows and pyroclastic deposits and marked by repeated eruption
stratovolcano/ composite
The Ring of Fire, a zone of concentrated volcanic activity encircling the Pacific Ocean basin, is located adjacent to ____
subduction zones
A slip is ____
the distance that rocks on opposite sides of a fault have moved
A handful of modeling clay held in both hands can be stretched out (plastic behavior) or snapped in half (brittle behavior). Which of the following factors is the most critical in determining this outcome?
the rate at which the strain is applied
Grabens form between two normal faults when ________
the rock has been pulled apart
Mount Pinatubo in the Philippines produced the greatest ash and sulfur clouds in the latter half of the 20th century. Satellite measurements show that the ________
total solar radiation reaching Earth's surface declined by 2 to 4 percent after the Pinatubo eruptions
A subduction complex contains slices of continental crust scraped from the top of a subducting plate
true
The Appalachian Mountains in the United States were formed by collision between ____
two continents
A subduction complex grows through the process of ________
underthrusting
Subduction of oceanic crust at a continental margin creates ____
underthrusting
S, or shear, waves _____________
vibrate perpendicular to the direction they travel
