geology test chapter 4

(fill in blank) which property of iron-bearing rocks provided evidence for the hypothesis of seafloor spreading?

magnetic orientation

when examining rocks from both sides of the mid-atlantic ridge, scientists found evidence for the phenomenon of

magnetic reversal

(fill in blank) iceland is growing due to its location on what geologic feature?

mid atlantic ridge

an underwater mountain chain formed with molten rock from seafloor spreading is called a

mid ocean ridge

as rock moves away from a mid ocean ridge, it is replaced by

molten rock

(fill in blank) what two types of crust make up the surface of the earth?

oceanic and continental

(fill in blank) what is the name for the huge landmass that wegener believed covered much of the earth 200 mil. years ago?

pangea

the german scientist alfred wegener proposed the existence of a huge land mass called

pangea

two plates grind past each other

transform fault boundary

(t/f) fossil records provide a clue to earlier positions of lithospheric plates

true

(t/f) island arcs form along convergent plate boundaries

true

(t/f) magma is the molten rock that wells up through fissures in the earth's crust

true

(t/f) many scientists believe that lithospheric plate movement is caused by temperature differences in the mantle

true

(t/f) movement of the earth's crust away from an oceanic ridge is called seafloor spreading

true

(t/f) the magnetic orientation of a rock is determined when the rock solidifies

true

(t/f) the mid atlantic ridge is an example of a divergent plate boundary

true

(t/f) the similar ages and types of rocks from western africa and eastern brazil support the theory of continental drift

true

(t/f) the theory of plate tectonics explains how some coastal mountain ranges may have been formed

true

which scientist first proposed that the continents were once joined in a single landmass called pangea?

wegener

which of the following may result from the collision of one plate with another?

a convergent boundary

the palo alto hills are probably an example of?

a suspect terrane

what evidence found in tropical regions of southern africa and south america most strongly supports the theory that the continents were once joined?

glacial debris

where in the earth do convection currents occur

in the asthenosphere

convection occurs because heated material becomes

less dense and rises

(fill in blank) according to the theory of continental drift, the eastern coast of south america was once joined to what continent?

Africa

to date, scientists have identified approximately

30 plates

(fill in blank) which theory states that new land is added to continental margins at subduction zones?

Theory of Suspect Terranes

paleomagnetism of the ocean floor is used to identify the

approximate time the rock cooled and hardened

(fill in blank) in which layer of the earth do convection currents occur?

asthenosphere

scientists think that the convection currents that are responsible for the movement of the lithospheric plates are found in the

asthenosphere

the earth's layer of solid rock that flows under pressure is called the:

asthenosphere

the layer of the mantle with plastic rock that underlies and moves the plate is the

asthenosphere

support for wegener's hypothesis of continental drift includes evidence of change in

climatic patterns

the term tectonics comes from a greek word meaning

construction

the theory of suspect terranes provides an explanation of how:

continents form

(fill in blank) what do scientists think is the cause of the movement of the earth's plates

convection currents

the collision of one lithospheric plate with another form a

convergent boundary

the type of collision that occurs when two lithospheric plates converge is determined primarily by plate

density

seafloor spreading occurs at which of the following plate boundaries?

divergent

seafloor spreading occurs at

divergent boundaries

two plates moving away from each other form a

divergent boundary

(fill in blank) what type of plate boundary causes extensive volcanic activity in iceland?

divergent plate boundaries

(t/f) a plate boundary at which one plate slides under another is called a transform fault boundary

false

(t/f) a rift valley is an example of a suspect terrane

false

(t/f) alfred wegener hypothesized that continents are fixed and unable to move

false

(t/f) all mid-atlantic ridge rock samples examined have proven to be older than the oldest-known continental rocks

false

(t/f) the earth's oldest rocks are found along the mid atlantic ridge

false

(t/f) the magnetic orientation of molten rock from a mid-ocean ridge will always reflect a reverse polarity of the earth's magnetic field at that time

false

(t/f) the theory of plate tectonics states that the earth's crust is made up of a single massive plate

false

which theory is most directly supported by the discovery of rocks similar in age and type in the areas shaded on the map?

plate tectonics

scientific evidence indicating that convection currents move the plates has been found by studying

rift valleys

new ocean floor is constantly being produced through the process of

seafloor spreading

the region along a plate boundary where one plate is forced under another plate is a

subduction zone

the region along lithospheric plate boundaries where one plate is moved beneath another is called a

subduction zone

(fill in blank) what is the term for a small piece of land that is scraped off descending ocean floor at a subduction zone?

terrane

geologists think that portions of the continents are made up formerly separate pieces of lithosphere called

terranes