ch 2 plate tectonics

t/f: subduction zones will only develop between a continental plate and an oceanic plate

false

part g: which supercontinent contained africa and south america?

gondwanaland

which of the following can be used to measure the rate of plate motion? choose all that apply.

gps satellites; the age of the seafloor at different locations

part e: which phenomenon can explain the presence of volcanoes in the middle of the pacific ocean?

hot spots

part f: what were the names of the two smaller super continents that formed when pangaea broke apart?

laurasia and gondwanaland

in which layer of the earth does the convection necessary for plate motion occur?

mantle

in the whole-mantle convection model, what feature balances the deeply descending lithosphere by transporting hot material toward the surface?

mantle plumes

which of the following statements explains why the presence of mesosaurus in both south america and africa supports the continental drift hypothesis?

mesosaurus was a freshwater aquatic reptile with fossil remains in both south america and africa

part d: which geologic features are associated with divergent boundaries?

mid-ocean ridges and continental rift valleys

part a: which of the following statements about tectonic plates is true?

most tectonic plates contain both oceanic and continental lithosphere

part b: complete this statement: Divergence is to moving away as convergence is to _______.

moving toward

part e: what forms at divergent plate boundaries?

new oceanic lithosphere

part c: do fracture zones near transform boundaries play a role in plate motion?

no, fracture zones play no role in plate motion

what direction was the pacific plate moving between 65 and 43 million years ago?

north

part e: which geologic features are associated with convergent boundaries?

ocean trenches and volcanoes

part f: in general, where do volcanoes form in subduction zones?

on the overriding plate, away from the convergent boundary

what is the name of the supercontinent proposed by alfred wegener?

pangaea

part a: how do plates move at divergent plate boundaries?

plates move apart

part b: how do plates move at convergent plate boundaries?

plates move toward one another

part c: how do plates move at transform plate boundaries?

plates slide past one another.

________ occurs when magnetic minerals in lavas align their magnetic fields with magnetic north, preserving a record of that pole's location at that moment in time.

preserved magnetism

before the 1960s, how did geologists view the ocean basins and continents of the earth?

scientists believed that all ocean basins and landmasses were permanently fixed in their position

lava solidifying during a period of reverse polarity will align the magnetic fields of its iron particles toward the ________ pole.

south

which two continents did Wegener cite as having the best evidence of a close coastline fit?

south america and africa

as the island of hawaii continues to move away from the mantle plume, a new submarine volcano will be created. off which coast would you expect the new submarine volcano to be forming?

southeast coast

part a: transform boundaries are classified under which type of fault?

strike-slip

part c: what was panthalassa?

the single ocean that existed after the pangaean supercontinent formed

which of the following pieces of evidence supports the plate tectonic theory?

the stripe patterns of high- and low-intensity magnetism are the same on both sides of an oceanic ridge

transform faults are different from convergent and divergent plate boundaries because

there is neither the creation nor the destruction of lithosphere at a transform fault, and plate movement is parallel to the length of a transform fault

part d: which plate boundary is NOT associated with volcanic eruptions?

transform

part b: what role do transform boundaries play?

transform boundaries connect other segments of plate boundaries

part d: what is the relationship between transform boundaries and mid-ocean ridges?

transform boundaries connect segments of mid-ocean ridges

part g: why are volcanoes NOT found at transform boundaries?

transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle

how can the orientation of transform faults provide information about the direction of plate motion?

transform faults are parallel to the direction of plate motion

part b: what is the relationship between continent edges and plate boundaries?

very few plate boundaries follow the edges of continents

why are the mid-ocean ridges higher in elevation than the surrounding ocean floor?

warmer material near the ridge is less dense, so it is more buoyant on the mantle

which feature of wegener's idea of continental drift contributed to its rejection by the scientific community?

wegener proposed that gravitational forces from the sun and moon could move continents

an important consequence of pangaea's breakup was the creation of which new ocean basin?

atlantic

in the mid-twentieth century and corroborated ever since, researchers dredging the seafloor could not find any materials older than ________.

180 million years

how are a continental volcanic arc and a volcanic island arc different from each other?

a continental volcanic arc is a result of an oceanic plate subducting under a continental plate, whereas a volcanic island arc is a result of an oceanic plate subducting under another oceanic plate

part d: what was the tethys sea?

a piece of the panthalassa ocean that existed after the pangaean supercontinent formed

part a: where are tectonic plates located?

at the earth's surface

part h: what is a volcanic arc?

a row of volcanoes that forms on the overriding plate near a subduction zone

what characteristic of a slab of oceanic lithosphere leads to the formation of deep-ocean trenches instead of shallow trenches?

a subducting oceanic plate forming a deep-ocean trench is older and denser than a subducting plate forming a shallow trench

part e: what was pangea?

a supercontinent that began to break apart about 200 million years ago

part f: where is the youngest ocean floor found?

along the crest of mid-ocean ridges

part h: the east african rift is a divergent plate boundary that is splitting the continent of africa into two pieces. what will eventually form around this divergent boundary?

an ocean

what is a mantle plume?

an upwelling of hot material from the Earth's interior that is cylindrical in shape

part i: which of the following mountain ranges are examples of continental arcs?

andes and cascades

when the continents were assembled and mountain ranges were matched up, mountains in scandinavia and the british isles matched up perfectly with which north american mountain range?

appalachian mountains

which of the following is consistent with the plate tectonic theory?

as a plate subducts into the asthenosphere, it pulls the trailing plate along

when considering evidence of glaciation on the southern continents, why did wegener reject the explanation that the entire planet had experienced a period of extreme cooling?

because geologic evidence supported the existence of tropical swamps in the northern hemisphere at the same time as the glaciers existing in the southern continents

name the early-twentieth-century hypothesis that was at first rejected by geologists and the more comprehensive theory that later replaced it.

continental drift hypothesis; theory of plate tectonics

which material is least dense?

continental lithosphere

part f: which type of plate boundary is most closely associated with uplifting continental regions and mountain building?

convergent bounderies

part d: in general, where do earthquakes AND volcanic eruptions occur? choose all that apply.

convergent plate bounderies; divergent plate bounderies

what two pieces of information would researchers need to have in order to calculate the rate of plate motion for seafloor spreading?

distance from the spreading center and age of seafloor at that distance

part b: what are the three types of plate boundaries?

divergent, convergent, and transform

part c: plates move apart at __________ boundaries, move together at __________ boundaries, and move side-by-side at __________ boundaries.

divergent; convergent; transform

part c: which of the following statements about earthquakes with magnitude greater than 4.0 is most accurate?

earthquakes with magnitude greater than 4.0 occur in a pattern than correlates closely with plate boundaries

part h: what caused the formation of the himalayas?

the collision of india with asia

part a: what is the relationship between the crust and lithosphere?

the crust is part of the lithosphere

part g: what would happen to earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?

the earth would increase in volume

what did wegener propose as the driving force behind continental drift?

the gravitational forces of the sun and the moon

which of the following were used by Wegener to support the continental drift hypothesis? choose all that apply.

the jigsaw fit of the continents, matching geologic units in the appalachian and caledonian Mountains, mesosaurus fossils found on south america and africa, major coal fields found in the eastern united states

why does oceanic lithosphere subduct under continental lithosphere, whereas continental lithosphere does not subduct under oceanic lithosphere?

the oceanic lithosphere is thinner and denser than the continental lithosphere, which is thicker and less dense

how old are the oldest sediments that have been recovered by deep-sea drilling? are they younger or older than the oldest continental rocks?

the oldest ocean sediments are 180 million years old and are younger than the oldest continental rocks on earth

what is the average rate of seafloor spreading occurring in the atlantic ocean and occurring in the pacific ocean?

the rate of seafloor spreading at the mid-atlantic ridge is 2 centimeters per year, whereas the rate of seafloor spreading at the east pacific rise is 15 centimeters per year

samples from the seafloor around the mid-atlantic ridge and the east pacific rise show that both areas have been creating new oceanic lithosphere in the last five million years. samples from the east pacific rise show the five-million-year-old seafloor is three times as wide as similarly aged material from the mid-atlantic ridge. What does this say about the rate of seafloor spreading in the east pacific?

the seafloor at the mid-atlantic ridge is growing more slowly than the east pacific rise