plate boundaries
in plate tectonics, intense geologic activity occurs at ---
continental drift
--- is the idea that continents move freely over Earth's surface, changing their positions
sea floor spreading
in this hypothesis the two sides of the mid-oceanic ridge are moving in opposite directions like slow conveyor belts
divergent
a --- plate boundary is where plates are moving away from each other
transform faults
the portion of a fracture zone between two offset portions of ridge crest is called a ---
graben
during extension in divergent plate boundaries a rift valley forms as a central ---
transform
these plate boundaries are marked by shallow-focus earthquakes in a narrow zone for a single fault or in a broad zone for a group of parallel faults
convergent
this type of plate boundary the two plates can consist of ocean-ocean, ocean-continent, or continent-continent crust
accretionary wedge
the inner wall of a trench consists of a(n) --- of thrust-faulted and folded marine sediment and pieces of oceanic crust
andesitic
--- volcanoes can be found along subducting plate boundaries
convection
Hess's original hypothesis was that sea-floor spreading is driven by deep mantle ---
sea floor moves
Harry Hess proposed that the ---
Pangea
Wegener reassembled the continents to form the super continent ---
slab pull
one possible mechanism for plate tectonic drive is ---
youngest on the crest of mid-ocean ridges
sea-floor spreading implies that sea-floor rocks should be ---
1 to 24
measured rates of sea-floor spreading range from --- cm/year
magnetic anomalies
marine geologists can predict the age of igneous rocks of the sea floor by measuring ---
oceanic trenches
the downward plunge of cold rock at convergent boundaries accounts for the existence of ---
diverging plate boundary
the Rift Valley in East Africa is an example of a ---
continent-continent convergent
one kind of convergent plate boundary is ---
lithosphere
the --- includes rocks of the crust and uppermost mantle
Alfred Wegener
In the early 1900s the German meteorologist --- made a strong case for continental drift
by continent-continent convergence
the Himalayan Mountains are thought to have formed ---
hot spots
Plumes from --- that are related to areas of active volcanism such as Iceland, Yellowstone, and Hawaii
vast fields of flood basalt
the head of large plumes that form "hot spots" may cause uplift and ---
northwest
the isotopic ages of Hawaiian Island basalts increase regularly to the ---
mid-ocean ridges
a divergent boundary on the sea floor is associated with ---
a transform fault
the San Andreas Fault is --- in California
Vine and Matthews
--- proposed an explanation for magnetic anomalies
ridge crests
the most common type of transform faults offset oceanic ---
the Red Sea
Divergent plate countries can occur where spreading occurs under a continent, for example ---
GPS
plate motion can be measured directly using ---
Nazca
the Peru-Chile trench is moving over the --- Plate as South America moves west
magmatic arc
alma heated by ocean-continent convergence may form a(n) --- such as the Aleutian Islands
polar wandering
the apparent movement of the magnetic poles through geologic time is called ---
all of the choices are correct
Evidence in support of continental drift includes ---
convergent boundaries
young mountain belts with their associated igneous intrusions, metamorphism, and fold-thrust belts form at ---
Gondwanaland
Pangea initially separated into two parts, the southern part is called ---
mid-ocean ridges
Alternating positive and negative polarity magnetic anomalies in the crust form a stripe-like pattern parallel to ---
plate tectonics
the basic idea of --- is that the Earth's surface is divided into a few large plates that move slowly relative to one another