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