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