Geology Chapter Three:
by comparing the patterns of magnetic reversals in a rock sequence, geologists can use the magnetic timescale shown here to estimate the ___ of a rock
age
where are earthquakes likely to occur
along continent edges and mid-ocean edges
what is a seamount
an eroded volcanic island beneath the sea surface
true/false: curved island arcs and linear island chains are very similar in their character and formation
false
plate boundaries are where most of earth's ___ occurs.
intense geologic activity
what specific type of plate boundary is commonly found in conjunction with mid-ocean ridges as it works to offset spreading and plate divergence
transform
the place where three plate boundaries meet is referred to as ___ junction
triple
which of the following are involved in the medicine triple junction
two different transform faults a subduction zone
convergent boundaries are formed by _____
two plates move toward each other
convergent boundaries are formed when ____
two plates move toward each other
when divergent boundaries occur on continents the process is called ___ rifting.
continental
when divergent boundaries occur on continents, the process is called ___ rifting
continental
the convergence of two continental masses is known as ___
continental collision
a divergent boundary can form within a continent. If it does, it is called a ___
continental rift
Gondwana is the name given to the combination of Southern ___ proposed by Wegener in his hypothesis of the continental drift
continents
large volcanoes of the andes mountains of South America and the cascade range of Washington and Oregon are the results of oceanic continental plate ____.
convergence
B
convergent
___ boundaries are formed when two plates move toward each other
convergent
red
convergent
when two ocean plates come together, a __ is formed.
convergent boundary
when two ocean plates come together, a ___ is formed
convergent boundary
the boundary between two plates may not have the same characteristics in different geographic locations because of ___
curves and abrupt bends that appear in boundaries between plates
as two oceanic plates diverge at mid ocean ridges, melting of the rising mantle occurs due to ___
decompression
mid-ocean ridges are elevated above the sea floor. the elevation of the sea floor ____
decreases away from the mid-ocean ridge because of the cooling and contraction of the rocks
mantle convection involves the asthenosphere moving upward due to its lower ____
density
A
divergent
yellow
divergent
volcanoes or earthquakes--which one is a better guide to plate boundaries on earth
earthquakes
which of the following statements about the distribution of earthquakes are accurate?
earthquakes are common along the western coats of north and south america there are a few earthquakes on the abyssal plains ocean trenches and associated island arcs have numerous earthquakes
this geographic area is the usual example geologists discuss when describing continental rifting in its different stages
east Africa
the direction of spreading along the north south ridges of the mid ocean ridge is ___
east west or perpendicular to the ridge
africa, antartica, South America, and North America, the other four continents are ____
europe australia asia africa
which of the magnetic strips have normal magnetic polarity?
1 and 3
plates move ___ per year
1 to 15 cm
if magnetic stripe is 120 km wide and formed over 4 million years, what would the rate of seafloor spreading be?
30 km/yr
oceans cover ___% of earth's surface
71
mid-ocean ridge
A
the five oceans
Atlantic Ocean Pacific Ocean article ocean southern ocean indian ocean
Deep ocean trench
B
mountain belt volcanoes and earthquakes
C
which tools can be used to directly measure plate motion
GPS Satellite lasers
geologists fit together the southern continents into the super continent
Gondwana
summarize the formation of the Atlantic Ocean by putting the stages in order
North America, South America, Europe, and Africa were all part of the same supercontinent. the crust underneath the supercontinent was uplifted by underlying magma moving toward the surface. the continental crust began to stretch, and a continental rift was formed. the rift split with supercontinent to form a narrow ocean basin. the ocean basin continued to widen through the seafloor spreading.
the figure shows the movement of __ over time to its current position, causing its unique plate tectonics
South America
the hypothesis of continental drift was not accepted because
Wegener could not explain how or why the continents moved from place to place
The pacific ring of fire is formed by ____
a string of volcanoes
regions of the deep ocean characterized by smooth ocean floor are ___
abyssal plains
when two oceanic plates converge, a curved belt of volcanic islands called an island __ can be formed
arc
when two oceanic plates converge, a curved belt of volcanic islands called an island ___ can be formed
arc
which of the following is not a characteristic of a mid ocean divergent boundary
as the plates move apart, solid lithosphere moves upward into the asthenosphere
rank the stages of the continental rifting
ascension of magma causes uplift of the crust stretching of the crust causes crustal blocks to drop into faults, forming a rift continuation of rifting splits the continent into two; a narrow ocean forms as seafloor spreading takes place continuation of seafloor spreading increases the ocean basin as it becomes wider
stages of the continental rifting
ascension of magma causes uplift of the crust stretching of the crust causes crustal blocks to drop into faults, forming a rift continuation of rifting splits the continent into two; a narrow ocean forms as seafloor spreading takes place continuation of seafloor spreading increases the ocean basin as it becomes wider.
if two continents are matched and their geologies are examined, it is assumed by plate tectonics that the mineral deposits discovered on one continent will ____
be the same on the other continent if the mineral deposits were formed before the continents split
The surface of the earth is notable for many geologic features including _____
beautiful valleys intricate coastlines undersea trenches dramatic mountains
convergence of two ocean plates forms an ocean-ocean convergent ____
boundary
the yearly rate of tectonic plate movement is best measured in ___
centimeters
both the matching of __ outlines and their geology help to support the theory of plate tectonics
contient
the convergence of two continental masses is known as a ____
contiental collision
both the matching of ___ outlines and their geology help to support the theory of plate tectonics
continent.
some continents continue outward from the shoreline under the seawater. these submerged benches are called ___ shelves
continental
land bridges were originally proposed to explain ____ evidence as provided by the presence of mesosaurus and glassopteris on continents separated by large oceans. One supercontinent that split apart by continental drift better explains this evidence
fossil
which pieces of evidence supported wagerers hypothesis of continental drift
fossils of animals and plants that existed more than 150 million years ago are pressed on several continents that are now divided by the ocean. similar rocks and geologic structures exist in South America, Africa, and Antartica. glacial evidence exists in places that are now close to the equator, and the direction of glacial movement indicates the continents were once joined. southern continental landmasses seem to fit together like puzzle pieces.
a transform fault on the ocean floor that is no longer active creates a step in seafloor elevation called a ___ zone
fracture
ridge push involves ___
gravity causing the plate to slide away from the topographically high ridge pushing the plate outward
which of the following are characteristics of a slab pull
gravity is a major force in slab pull. subjecting plates move faster than nonsubducting plates. subducting oceanic lithosphere is denser than asthenosphere.
besides creating and destroying lithosphere, plate tectonic processes also transport ___ from the center of earth to the surface
heat
as plates move over ___ island chains within oceans can be formed by volcanism
hot spots
Which of the following are characteristics of continental rifting
if rifting continues, the continent can be split into two pieces rifting begins with a broad uplift as magma ascends stretching of the crust caused crustal blocks to drop down
which of the following are characteristics of continental rifting
if rifting continues, the continent can be split into two pieces rifting begins with a broad uplift as magma ascends stretching of the crust causes crustal blocks to drop down
which of the following does not describe continental rifting
if rifting continues, the continent will remain intact
according to plate tectonics, oceanic crust forms from upwelling magma that spreads outward from a mid-ocean ridge. Which of the following statements support this?
if this is true, then the oldest basalt should be the farthest from the mid-ocean ridge. if this is true, the thickest sediment cover should be farthest from the mid-ocean ridge.
an accretionary prism of sediments and oceanic crust is formed ___
in an oceanic trench created by the subduction of one oceanic plate beneath another plate
the majority of transform boundaries are located ___
in conjunction with mid-ocean ridges
when two oceanic plates converge some magma erupts under the ocean, forming volcanoes that may rise above the sea. these volcanoes form a curved ___
island arc
curving island chains across the seafloor that are mainly volcanic in origin are called ___
island arcs
tectonic plates are composed of ___ and move around on top of the asthenosphere
lithosphere
the process of plate tectonics circulates materials between the athenosphere and the ___
lithosphere
____ patterns develop on the seafloor as iron-rich minerals in newly erupted basaltic lava align with earth's magnetic poles
magnetic
earth's ___ poles have switched many times throughout geologic history
magnetic
the arrow in the figure is pointing to ___ where the African and South American plates are moving apart and new oceanic lithosphere is emerging from earth's mantle
mid-atlantic ridge
what three accurate pieces of information can be obtained from the graph
midway is the oldest of the listed islands kauai is closer to kiluea than midway kauai is younger than midway
exemplified by the western coasts of north and South America, high elevations on earth tend to have ___ earthquake and volcanic activity than lower elevation areas
more
the western margin of South America is ___ whereas the eastern margin has much less relief which reflects the different tectonic plate settings that surround the continent
mountainous
western side
mountains trench subduction zone
enormous mountain belts and high plateaus are formed when two continental plates collide as ___
neither is subducted
basalt forming today from cooling magma at the mid-ocean ridge would have ___ polarity
normal
earth's magnetic field currently flows from south to north. we refer to this orientation as ___ polarity
normal
abyssal plains are the relatively smooth surfaces of the ___ floor
ocean
abyssal plains are the relatively smooth surfaces of the ___ floor.
ocean
cracks and steps that cross the seafloor and run at right angles to mid ocean ridges are called ___
ocean fracture zones
mid-ocean ridges are broad symmetrical ridges that cross ___ basins
oceanic
oceanic plates subduct beneath continental plates because ____
oceanic plates are dense and continental plates are buoyant
convection currents in earth's ___ core produce the magnetic field
outer
convection currents in earths ___ core produces the magnetic field
outer
the layer of earth that behaves as a dynamo (electrical generator), producing the magnetic field is the _____
outer core
subduction on both sides of the ___ ocean produces the ring of fire
pacific
volcanic and earthquake activities on earth can mostly be explained by the interaction between plates. however, volcanoes and earthquakes do occur at places other than at plate boundaries. an explanation for this is ____
parts of the lithosphere are weaker so forces can be transmitted through plates causing geologic activities in the weaker areas
GPS and lasers are used to directly measure the motion and direction of tectonic ___ on earth
plates
as ___ move over hot spots, island ___ in oceans can be formed by volcanism
plates chains
for a plate to move the driving forces must exceed the __ forces
resisting
for a plate to move, the driving forces must exceed the ___ forces
resisting
the ___ ___ fault in California is a transform fault that has formed linear valleys, abrupt mountain fronts, and lines of lakes
san Andreas
Harry hess and Robert Dietz proposed that the oceanic crust in the Atlantic Ocean was spreading apart at the mid Atlantic ridge and that this process moved the continents apart from one another. This process is called ____
seafloor spreading
the image shows the mid Atlantic ridge, a submarine volcanic mountain belt that is a key location in the process of ___. This hypothesis was developed by Henry hess and Robert Dietz
seafloor spreading
A mountain beneath the ocean that does not reach the surface is called ___. It may be worn-down island or may never have been tall enough to break the water surface.
seamount
this is the name of a volcanic island that erodes and sinks underneath the sea surface
seamount
which of the following statements are true about characteristic geologic features with respect to their locations on earth
seamounts can be part of the island arcs smooth regions of the ocean floor are called abyssal plains mid-ocean ridges and their fracture zones encircle much for he globe continents and oceans can have elevated areas called plateaus continental shelves are extensions of continents beneath the oceans
how many major continents are there on earth
seven
at mid ocean ridges as two plates diverge, ____
solid mantle in the asthenosphere rises toward the surface and begins to melt due to decompression
glacial evidence in ___ continents that are too warm for glaciers in their current position is evidence of continental drift
southern
earthquakes are common along the western coast of South America as a ___ zone occurs due to oceanic lithosphere moving beneath the continent
subduction
the process of one plate sliding beneath another plate is called ____
subduction
how is magma created in a subduction zone
subduction brings one plate to a depth hot enough for minerals to release water; this water causes melting in the overlying asthenopshere
a ___ is formed when one plate slides beneath another
subduction zone
Earth's ____ is notable for many geologic features such as beautiful valleys, intricate coastlines, and deep ocean trenches
surface
___ plates are composed of lithosphere and move around on the asthenosphere
tectonic
___ is the study of processes that deform the crust and the mantle
tectonics
continental outlines and similar geology on neigh boring continents support the theory of plate
tectonics
the zigzag pattern of mid-ocean ridges reflects the alternation of the spreading segments with ___ faults
transform
which of the following statements are accurate about what happens when two oceanic plates converge
temperates increase within the subduction zone, releasing water which induces melting one of the tow oceanic plates subduct beneath the other plate an oceanic trench is formed and sediments begin to collect buoyant magma rises into the overlying plate
in order for a tectonic plate to move, what must the relationship between driving and resisting forces be?
the driving forces must exceed the resisting forces
along the boundary of an oceanic continental convergence
the oceanic plate subduct beneath the continental plate
the volcanic island chain known as the Hawaiian island differs from the Galapagos islands because
the plate moving over the hot spot that formed the Hawaiian island has been moving faster
what is the underlying geologic expo;anation for why western South America is so different from eastern South America
the western side is a plate boundary and the eastern side is not
why do opposite sides of a fracture have different elevations
they are different ages, so they have different cooling histories
C
transform
a fault that accommodates the horizontal movement of one tectonic plate past another is ___ fault
transform
an ocean fracture zone is a former __fault that now has no relative motion along it
transform
green
transform
horizontal movements between plates occur at ___ faults
transform
the type of fault that accommodates horizontal movements between plates is a ___ fault.
transform
which of the following statements are accurate about volcano distributions on earth
volcanism occurs along mid-ocean ridges. many volcanoes along the edge of the Pacific Ocean are associated with earthquakes there is a large volcanic belt along the west coasts of north and South America
island and seamount chains are formed by __ and hot spot activity
volcanoes
areas that represent convergent boundaries
volcanoes in the andes mountains of South America volcanoes of southern British Columbia volcanoes of the cascade range in the us pacific northwest
eastern side
wide continental shelf lack of tectonic activity passive margin
