Geology
A _____ plate boundary is where plates are moving away from each other.
divergent
Most of the evidence for magnetic reversals comes from lava flows on the continents.
true
Seismic waves travel faster in oceanic crust than in continental crust.
true
Submarine canyons are erosional features.
true
Terrigineous sediment is sediment derived from the land.
true
The Moho separates the crust from the mantle.
true
The San Andreas Fault is a transform fault.
true
The Vine-Matthews hypothesis provided a means to measure the rate of sea-floor spreading.
true
The boundary between the core and the mantle is marked by great changes in ____.
Seismic velocity, density, and temperature are all correct.
A tsunami has a small wave height, travels rapidly, and is not noticed by people in boats.
True
Convergent boundaries, due to their geometry, are the sites of the largest earthquakes on Earth.
True
Deeply buried rock that is hot and under pressure can deform like taffy or putty.
True
Earth's lithosphere is made up of the uppermost part of the mantle and crust.
True
Geology uses the scientific method to explain natural aspects of the Earth.
True
Rocks brought to the earth's surface by internal processes are worn down, and eroded by surficial processes.
True
A deviation from average reading is called a(n) ____.
anomaly
Many guyots and seamounts are aligned in chains (for example the Hawaiian Islands and Emperor seamounts) that form major _____.
aseismic ridges
The ____ is a low velocity seismic zone.
asthenosphere
The ____ is soft and therefore flows more readily than the underlying mantle.
asthenosphere
_____ parallel the shore, but are separated from it by wide, deep lagoons.
barrier reefs
The _____ crust of the sea floor is covered in many places with layers of sediment.
basalt
The P-wave shadow zone can be explained by the refraction of P-waves at the ___.
core mantle boundary
The concept of isostatic adjustment implies that all mountains extend to the same depth in the mantle.
false
The deepest places on Earth, more than 11 km below sea level, are the abyssal plains.
false
Wegener reassembled the modern continents to form the giant super continent of Gondwanaland.
false
Abyssal fans are made up of _____ sediment that has moved down submarine canyons
land derived
One widely accepted hypothesis is that the Earth's magnetic field is created by electric currents within the ______.
liquid outer core
Oceanic trenches are marked by _______.
low heat flow
The downward plunge of cold rock at convergent boundaries accounts for the existence of _____.
oceanic trenches
The asthenosphere is a mantle zone of low seismic wave velocity that behaves in a ductile manner.
true
A cavity or body of low-density material causes a _____ pull on a gravity meter relative to average crust.
weaker
Most geologists think that the flat summits of seamounts ___.
were eroded flat by wave action
The North American plate is moving ____.
west
Sea-floor spreading implies that sea-floor rocks should be ______________.
youngest on the crest of mid ocean ridges
Water depth increases over a continental shelf to the outer edge depth of _____ to ____ meters.
100/200
The magnetic poles are displaced about ______ degrees from the geographic poles.
11.5
A gravity reading lower than the normal regional gravity indicates that a region is ____.
being held down
The crust and upper mantle form the ____.
lithosphere
Measured rates of sea-floor spreading range from ______ cm/year.
1 to 24
Seismic surveys of the sea have shown the oceanic crust to be divided into _______ major layers.
3
The best geologic data currently available indicates that Earth is approximately ___ years old.
4,550,000,000
Fossil evidence indicates that complex life forms, capable of generating easily fossilized hard parts like shells or bones, have existed in abundance on Earth since approximately ___ years ago.
544 million
Oceans cover _____ percent of the Earth's surface.
70
In the early 1900s the German meteorologist _____ made a strong case for continental drift.
Alfred Wegener
____ volcanoes can be found along subducting plate boundaries.
Andesitic
Because _____ can be accurately calculated, the size and shape of the core can be determined.
P wave paths
Divergent plate boundaries can occur where spreading occurs under a continent, for example ___.
the red sea
Hot mantle rock rising slowly by convection under parts of the ocean explains ____.
the unexpectedly high heat flow under the oceans
A _____ is a scientific concept that has been tested and is in all likelihood true.
theory
A _____, by scientists definition, is something that has been overwhelmingly verified.
theory
Continental crust is ___ relative to oceanic crust.
thicker
Oceanic crust is _____ continental crust.
thinner than
These plate boundaries are marked by shallow-focus earthquakes in a narrow zone for a single fault or in a broad zone for a group of parallel faults.
transform
Turbidity currents flow down the continental slope until they come to rest on ___.
the abyssal plain
While the reserves of petroleum hydrocarbons within the United States are limited, other geologic resources (iron, aluminum, copper, and tin) are available in great abundance.
False
Plate motion can be measured directly using ____.
GPS
Pangea initially separated into two parts, the southern part is called ____.
Gondwanaland
The Earth can be considered as interrelated systems or spheres.
True
The Earth is about 4.6 billion years old.
True
The North American Plate is all on one plate.
True
The mantle is the most voluminous of Earth's three major concentric zones.
True
Understanding geology can help us lessen or prevent damage to the environment.
True
We depend on geologists for the raw materials we need for survival
True
A ______ is a huge ocean wave usually caused by a displacement of the sea floor and commonly associated with massive earthquakes.
Tsunami
One kind of convergent plate boundary is ____.
continent-continent convergence
The two major types of crust are oceanic crust and __.
continental crust
____ is the idea that continents move freely over Earth's surface, changing their positions relative to one another.
continental drift
The ____ is a shallow submarine platform at the edge of a continent.
continental shelf
The continental shelf is part of the ____.
continents
_____ currents are bottom currents that flows parallel to the slopes of the continental margin.
contour
A ______ is a bottom flowing current that flows parallel to the slopes of the continental margins.
contour current
Hess's original hypothesis was that sea-floor spreading is driven by deep mantle ____.
convection
_____ is a circulation pattern in which low-density material rises and high-density material sinks.
convection
A _______ boundary occurs where plates move towards one another.
convergent
This type of plate boundary the two plates can consist of ocean-ocean, ocean-continent, or continent-continent crust.
convergent
Young mountain belts with their associated igneous intrusions, metamorphism, and fold-thrust belts form at _______.
convergent boundaries
Iron-nickel meteorites are an important source of information regarding the composition of Earth's ______.
core
Listed from Earth's center outward, the three concentric zones of Earth are the __.
core, mantle, crust
The _______ collectively make up the lithosphere.
crust and the uppermost part of the mantle
The rise of the crust after removal of ice is called ____.
crustal rebound
As lava cools below the _____ point, a record of the Earth's magnetic field is permanently trapped in the rock.
curie
The ____ is the transition zone at the core-mantle boundary.
d layer
Heat flow ______ the crest of the mid-oceanic ridges.
decreases away from
The _____ of old seafloor takes place at convergent boundaries.
destruction
The Rift Valley in East Africa is an example of a _____.
diverging plate boundary
In a passive continental margin, there is a lack of _______.
earthquakes , volcanos, and young mountain belts
A basic tool for indirectly studying the sea floor is the ____, which measures water depth.
echo sounder
Recently, geologists have been analyzing ____ generated by tidal friction, ocean waves, and storms to gain an even more detailed image of the crust and upper mantle.
energy waves
_______ takes place where moving water, ice, and wind loosen and remove material on the continents.
erosion
Most seamounts are ______.
extinct volcanoes
A region held down out of isostatic equilibrium produces a negative gravity anomaly.
false
A tectonic plate is always made up of a combination of continental and oceanic crust.
false
All rocks and sediments of the sea floor are more than 3 billion years old.
false
All transform faults connect two ridge segments.
false
An oceanic trench is a deep narrow rift parallel to the crest of a mid-oceanic ridge.
false
Continental drift is the hypothesis that the sea floor forms at the crest of the mid-oceanic ridge, then moves horizontally away from the ridge crest.
false
Continental slopes are often marked by lines of hot springs that precipitate metals.
false
Generally, seismic wave velocity decreases with depth.
false
Geologists think that the asthenosphere is molten.
false
Guyots and seamounts are scattered randomly on the sea floor.
false
Lithosphere is remarkably constant in thickness across ocean basins.
false
Most seamounts are active volcanoes.
false
Ophiolitic sediment is composed of wind-blown dust and microscopic skeletons that settle slowly to the sea floor.
false
Passive margins are found on the edges of most of the landmasses bordering the Pacific Ocean.
false
Pelagic sediment is sediment that settles slowly through the ocean water.
false
Recent studies using seismic tomography indicates that whole mantle convection is the best model.
false
Suture zones in continents mark old sites of mantle plumes.
false
The Earth's core is made up of equal parts cobalt and iron.
false
The average density of the Earth is 2.7 gm/cm3.
false
When a ridge subsides sea level may rise.
false
Which of the following lifeforms appeared first in the geologic record?
fishes
_____ are major lines of weakness in Earth's crust that cross the mid-oceanic ridge at right angles.
fracture zones
Earthquakes, volcanic eruptions, landslides, floods, and tsunamis are all examples of:
geologic hazards
___ refer(s) to the scientific study of Earth.
geology
_____ is the branch of geology that applies physical laws and principles to study Earth.
geophysics
During extension in divergent plate boundaries a rift valley forms as a central ____.
graben
Turbidity currents are great masses of sediment-laden water that are pulled downhill by ____.
gravity
A ____ is a tool used to study the gravitational attraction between Earth and a mass within the instrument.
gravity meter
High _____ is usually an indication of a magma body or still-cooling pluton near the surface.
heat flow
The gradual loss of heat through the Earth's surface is called ___.
heat flow
Plumes form ______ that are related to areas of active volcanism such as Iceland, Yellowstone and Hawaii.
hot spots
Mid-oceanic ridges are often marked by lines of _____ that carry and precipitate metals.
hot springs
Rock deep within the Earth is _____ and ______.
hot/ heat flows out towards earth surface
Among other things, geologists are employed as __.
hydrogeologists, petroleum geologists, environmental geologist, marine geologist
The Earth's system that includes the oceans, rivers, lakes, and glaciers of the world is called the _______.
hydrosphere
After data have been analyzed, tentative explanations or solutions called _____ may be proposed.
hypothesis
A gravity meter registers _____ over ore bodies.
increased gravity
The continental shelves of the world are typically covered by relatively young sediments derived from ___________.
land
With the cementation of loose particles sediment becomes ______.
lithified
The ___ includes rocks of the crust and uppermost mantle.
lithosphere
The concept of plate tectonics regards the earth's ___ as broken into a number of ___ that are in motion relative to each other.
lithosphere/ plates
Magma heated by ocean-continent convergence may form a(n) _____ such as the Aleutian Islands.
magmatic arc
Marine geologists can predict the age of igneous rocks of the sea floor by measuring _____.
magnetic anomalies
A region of magnetic force, called the ______ surround Earth.
magnetic field
The _______ is the most voluminous of the Earth's three major concentric zones.
mantle
Evidence in support of continental drift includes ____.
matching of geologic patterns on continents, fit of continental margins, glacial striation patterns, and fossil distribution on different continents
Sedimentary rock that becomes deeply buried may be transformed by heat and pressure into _______ rock.
metamorphic
Shallow focus earthquakes on the sea floor are associated with ___.
mid ocean ridge crests
A divergent boundary on the sea floor is associated with ______.
mid oceanic ridges
Alternating positive and negative polarity magnetic anomalies in the crust form a stripe-like pattern parallel to _____.
mid oceanic ridges
Project FAMOUS used submersibles to study ______.
mid-ocean ridges
The boundary that separates the crust from the mantle is the ____.
mohorovicic discontinuity
The Earth's interior heat engine works because hot buoyant material deep within the Earth _______ while cold denser material _______.
moves upward/ moves downward
Eruptive activity at the summit of the Nevada del Ruiz volcano in Colombia in 1985 caused snow and ice to melt, generating a ___ that killed 23,000 people in the village of Armero.
mud flow
The Peru-Chile trench is moving over the ________ Plate as South America moves west.
nazca
The isotopic ages of Hawaiian Island basalts increase regularly to the ____.
northwest
Where a subducting plate slides beneath the lithosphere, melting takes place and a(n) ____ is created.
ocean trench
Earthquakes, volcanoes, Benioff seismic zones, and island arcs are all associated with this sea floor feature.
oceanic trench
Geologists' ideas about the composition of ocean crust are greatly influenced by the study of ____.
ophiolites
The study of ancient magnetic fields is called ____.
paleomagnetism
Wegener reassembled the continents to form the super continent _____.
pangea
At a pressure equivalent to a depth of 670 km the mineral olivine collapses to form ____.
perovskite
_____ are rounded masses of rock that form when molten lava erupts into cold water.
pillow lava
In plate tectonics, intense geologic activity occurs at ____.
plate boundaries
The basic idea of ______ is that the Earth's surface is divided into a few large plates that move slowly relative to one another.
plate tectonics
The apparent movement of the magnetic poles through geologic time is called _____.
polar wandering
Disintegration of rock at Earth's surface may be facilitated by water __.
present as vapor in the atmosphere, moving through near surface pores and fractures, frozen in glacier that is flowing over the surface, flowing on the surface in streams and as runoff
A ___ is a hot, turbulent mixture of expanding gases and volcanic ash that flows rapidly down the side of a volcano.
pyroclastic flow
The bending of seismic waves as they pass from one material to another is called seismic ____.
refraction
The rock record for tens of millions of years indicates that the Earth's magnetic field ____.
reverses polarity about every 500,000 years
The most common type of transform faults offset oceanic ____.
ridge crests
The crests of mid-oceanic ridges are associated with ____.
rift valleys
Harry Hess proposed that the _______.
sea floor moves
In this hypothesis the two sides of the mid-oceanic ridge are moving in opposite directions like slow conveyor belts.
sea floor spreading
The study of _____ rocks, sediment, and topography provided most of the information that led to the concept of plate tectonics.
seafloor
The product of the breakdown of surface rocks by weathering and erosion is __.
sediment
A(n) ___ may eventually be formed as layers of sediment are buried by subsequent layers of sediment.
sedimentary rock
Detailed images provided by _____ suggest that the mantle is heterogeneous, probably due to variations in temperature, composition, and density.
seismic reflection
_____ is the return of some of the energy of a seismic wave to the Earth's surface after it bounces off a rock boundary.
seismic reflection
This instrument works on essentially the same principles as echo sounder but can penetrate the bottom of the sea floor and provides more information.
seismic reflection profiler
One possible mechanism for plate tectonic drive is ____.
slab pull
Earth can be visualized as a giant machine driven by which of the following engines?
solar and internal
Earth's external heat engine is driven by __.
solar power
_____ are V-shaped valleys that run across continental shelves and down continental slopes.
submarine canyons
These machines can take geologists to many parts of the sea floor to observe, photograph, and sample rock and sediment.
submersibles
To understand geology one must understand how the solid Earth interacts with water, air, and living organisms. For this reason, it is useful to think of Earth as being part of a ____.
system
_______ are geological forces generated inside the Earth.
tectonic forces
___ indicates that the core of the Earth is a liquid.
the S wave shadow zone
The average temperature increase in the shallow crust (the geothermal gradient) is about ______ degrees C per kilometer.
25
Fossil evidence indicates that dinosaurs became extinct approximately ___ years ago.
65 million
______ proposed that the three types of coral reefs are related to each other by subsidence of a central volcanic island.
Charles Darwin
A transform plate boundary occurs where two plates converge.
False
After the opening of the North Slope in Alaska the U.S. stopped importing petroleum.
False
Most convergent plate boundaries coincide with the crests of submarine mountain ranges called mid-oceanic ridges.
False
Most deaths associated with volcanic eruptions are due to burns of lava flows.
False
Ocean - ocean plate convergence formed major mountain belts such as the Andes and Cascades.
False
Plate tectonics regards the lithosphere as divided into segments (plates) that are in horizontal motion.
False
Rocks formed at high temperatures and under high pressure deep within the Earth and pushed upward by tectonic force are stable in their new environment.
False
The abyssal plains are formed of _____.
Horizontal layers of sediment
_______ is an island on a mid-oceanic ridge.
Iceland
_______ is a balance or equilibrium of adjacent blocks of brittle crust floating on the upper mantle.
Isostasy
_____ predicts that the higher a mountain range extends above sea level the deeper it extends into the mantle.
Isostatic adjustment
What is the asthenosphere?
It is the zone of weakness in the mantle on which the lithosphere moves.
The _____ and the Alpine Fault of New Zealand are examples of transform plate boundaries.
San Andreas Fault of California
A hypothesis that passes repeated tests ultimately becomes __.
a theory
Thick deposits of sediment called _____ are found at the base of many submarine canyons.
abyssal fans
The continental rise typically ends at a(n) _______ at a depth of about 5 kilometers.
abyssal plain
The inner wall of a trench consists of a(n) _____ of thrust-faulted and folded marine sediment and pieces of oceanic crust.
accretionary wedge
Plates are known to be moving away from each other __.
across mid ocean ridges
A(n) _____ continental margin usually lacks a continental rise and an abyssal plain and is associated with convergent plate boundaries.
active
__________ is the name applied to hot springs on the seafloor where 350 degree Celsius metal-rich solutions are discharged into the cold waters of the ocean.
black smokers
The Himalayan Mountains are thought to have formed ____.
by continent-continent convergence
The San Andreas Fault is _________ in California.
transform fault
The portion of a fracture zone between two offset portions of ridge crest is called a ____.
transform fault
Seismic P-waves _____ through continental crust relative to oceanic crust.
travel slower
A contour current is a bottom current that flows parallel to the slopes of the continental margin.
true
A gravity meter can be used to explore for metallic mineral deposits.
true
A rift valley runs down the crest of most mid-oceanic ridges.
true
Abyssal plains are the flattest features on Earth.
true
An island arc is a string of volcanoes parallel to the oceanic trench
true
As a descending plate reaches depths of about 100 km, magma is generated in the overlying asthenosphere.
true
Atolls are circles of reefs that rim lagoons.
true
Continental drift incorporated sea floor spreading into the new concept of plate tectonics.
true
Geologists study the composition of the Earth's crust using deep drill holes.
true
Magma that is created by ocean-continent convergence forms either island arcs or belts of igneous activity on the edges of continents.
true
Ocean water originated mainly from degassing of the Earth's interior.
true
Oceans cover more than 71% of the Earth's surface.
true
Pangea initially separated into two parts, a northern supercontinent, and a southern supercontinent.
true
Seismic tomography uses earthquake waves and computers to study cross sections of the mantle.
true
The asthenosphere may be a partially melted crystal and liquid slush.
true
The average heat flow of the continents is the same as the average heat flow of the sea floor.
true
The composition of the upper mantle is the ultramafic rock peridotite.
true
The continental rise is a wedge of sediment that extends from the lower part of the continent slope to the deep-sea floor.
true
The downward plunge of cold lithosphere accounts for the existence of oceanic trenches as well as their low heat flow.
true
The force of gravity between two objects decreases as the square of the distance between the objects increases.
true
The greatest negative gravity anomalies in the world are found over oceanic trenches.
true
The island of Iceland appears to be an exposed section of the Atlantic mid-oceanic ridge.
true
The ocean became salty as water picked up chlorine from volcanic gases and sodium and magnesium from weathering of minerals at the Earth's surface.
true
The portion of a fracture zone between two offset portions of a ridge crest is called a transform fault.
true
The presence of an S-wave shadow zone implies that the Earth's core is liquid.
true
The rise of the surface of the crust after removal of glacial ice is known as isostatic rebound.
true
The way that P-waves are refracted within the core suggests that there is a solid inner core.
true
Wegener's theory of continental drift proposed that the continents plowed through oceanic crust.
true
Young mountain belts, with their associated igneous intrusions, metamorphism, and fold-thrust belts, form at convergent boundaries.
true
The Grand Banks cable breaks of 1929 are interpreted to be the result of earthquake-caused ____.
turbidity currents
A(n) _____ is a great mass of sediment-laden water that is pulled downward by gravity along the continental slope.
turbidity flow
The upper mantle consists of _______.
ultramafic rocks
The head of large plumes that form "hot spots" may cause uplift and ____.
vast fields of flood basalt
_______ proposed an explanation for magnetic anomalies.
vine and matthews
Plate tectonics is a unifying idea that helps explain where and why there are ___ on Earth.
volcanoes, earthquakes, mountain belts, oceanic ridges and trenches