plate tectonics Flashcards
continental drift, oceans, margins and landforms
what rate do tectonic plates moce at?
1 to 15cm/ year
what is oceanic crust mainly composed of?
basalt
how are igneous rocks formed?
through the freezing or crystallization of a melt
compared to coarse- grained igneous rocks, fine grained igneous rocks…?
cool and solidify more quickly
what plate boundary do deep ocean trenches occur at?
convergent
where is the youngest seafloor found?
along mid ocean ridges
where are subduction zones found?
convergent plate boundaries
on either side of a mid ocean ridge, the lithosphere begins to…?
sink as it cools and contracts
why are mid -ocean ridges elevated sbove the surrounding seafloor?
ridge rocks are hot and therfore have a lower density
why was Wegeners theory of continetal drift rejected at first?
Wegener could not provise a diving force
where, along the sea floor, is the rate of geothermal heat flow the greatest?
along mid ocean ridges
why does oceanic lithoshpere get thicker away from mid ocean ridges?
the addition of new lithospheric mantle as a result of cooling
where can evidence of paleomagnetism be found?
basalt that has cooled from lava, any rock with minerals present and in sedimentary rocks where minerals form from ion- bearing groundwater
how old are the oldest basalts on the ocean floor?
around 200 million
where is the thickness of clay and planktonic microskeletons the greatest?
at the edges of ocean basins?
what plate boundary is iceland located on?
divergent
what is a guyot?
an exitinct oceanic hot-spot volcano that has subsided below sea level
according to Archimedes’ priciple of buoyancy, an iceburg sinks until..?
the total mass of the water displaced equals the total mass of the whole iceburg
what is an active margin?
a continetal coastline that coincides with a plate boundary
most of the pulling force driving plate motion is produced at…?
subduction zones
You are studying the seismic data from Mars when you notice that there are no S-waves recorded from 130° through 180° on the opposite side of the planet. What does this information tell you about the interior of Mars?
there is a layer of liquid material in the interior of mars
what is an example of a present dat island arc?
teh Aleutian Islands of Alaska
the thickness of oceanic lithosphere is…?
least near the mid ocean ridges and thickens away from the ridges
describe rock produced at mid ocean ridges
basalt is produced at shallow depths and gabbro at deeper depths
where does a volcanic island arc form?
where an oceanic lithosphere subducts beneath another oceanic lithosphere plate
which 2 types of plate boundaries are found linked together at mis ocean ridges?
divergent and transform
can s waves or p waves travel through liquids?
p waves
do seismic waves travel faster in solids or liquids?
solids
why does slab pull occur?
subducting slabs are cooler, and therfore more dense than the surrounding aesthensphere
can the age of the earth be relaibly estimated from sediment thickness?
no - much of earths history is prepresented by uncomformities between strata rather than strata themselves
If a P-wave is traveling through sandstone and then encounters peridotite, the P-wave will …?
speed up - a sandstone is a crustal (in fact sedimentary) rock; and remember that peridotite is a mantle rock. Then you would remember that the seismic velocity in the mantle is higher than in the crust - and you could guess that this must also be true for its actual rock types.
example of a coninental volcaninc arc?
the Andes
If an S-wave is traveling through rock when it encounters a magma chamber, the S-wave will…?
not travel through the magma
where is most of the PUSHING force driving plate motion produced?
at mid ocean ridges
at at subduction zone, is the overriding plate oceanic or continental lithosphere?
may be both
