plate tectonics

Question 1

what rate do tectonic plates moce at?

Answer 1

1 to 15cm/ year

Question 2

what is oceanic crust mainly composed of?

Answer 2

basalt

Question 3

how are igneous rocks formed?

Answer 3

through the freezing or crystallization of a melt

Question 4

compared to coarse- grained igneous rocks, fine grained igneous rocks…?

Answer 4

cool and solidify more quickly

Question 5

what plate boundary do deep ocean trenches occur at?

Answer 5

convergent

Question 6

where is the youngest seafloor found?

Answer 6

along mid ocean ridges

Question 7

where are subduction zones found?

Answer 7

convergent plate boundaries

Question 8

on either side of a mid ocean ridge, the lithosphere begins to…?

Answer 8

sink as it cools and contracts

Question 9

why are mid -ocean ridges elevated sbove the surrounding seafloor?

Answer 9

ridge rocks are hot and therfore have a lower density

Question 10

why was Wegeners theory of continetal drift rejected at first?

Answer 10

Wegener could not provise a diving force

Question 11

where, along the sea floor, is the rate of geothermal heat flow the greatest?

Answer 11

along mid ocean ridges

Question 12

why does oceanic lithoshpere get thicker away from mid ocean ridges?

Answer 12

the addition of new lithospheric mantle as a result of cooling

Question 13

where can evidence of paleomagnetism be found?

Answer 13

basalt that has cooled from lava, any rock with minerals present and in sedimentary rocks where minerals form from ion- bearing groundwater

Question 14

how old are the oldest basalts on the ocean floor?

Answer 14

around 200 million

Question 15

where is the thickness of clay and planktonic microskeletons the greatest?

Answer 15

at the edges of ocean basins?

Question 16

what plate boundary is iceland located on?

Answer 16

divergent

Question 17

what is a guyot?

Answer 17

an exitinct oceanic hot-spot volcano that has subsided below sea level

Question 18

according to Archimedes’ priciple of buoyancy, an iceburg sinks until..?

Answer 18

the total mass of the water displaced equals the total mass of the whole iceburg

Question 19

what is an active margin?

Answer 19

a continetal coastline that coincides with a plate boundary

Question 20

most of the pulling force driving plate motion is produced at…?

Answer 20

subduction zones

Question 21

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?

Answer 21

there is a layer of liquid material in the interior of mars

Question 22

what is an example of a present dat island arc?

Answer 22

teh Aleutian Islands of Alaska

Question 23

the thickness of oceanic lithosphere is…?

Answer 23

least near the mid ocean ridges and thickens away from the ridges

Question 24

describe rock produced at mid ocean ridges

Answer 24

basalt is produced at shallow depths and gabbro at deeper depths

Question 25

where does a volcanic island arc form?

Answer 25

where an oceanic lithosphere subducts beneath another oceanic lithosphere plate

Question 26

which 2 types of plate boundaries are found linked together at mis ocean ridges?

Answer 26

divergent and transform

Question 27

can s waves or p waves travel through liquids?

Answer 27

p waves

Question 28

do seismic waves travel faster in solids or liquids?

Answer 28

solids

Question 29

why does slab pull occur?

Answer 29

subducting slabs are cooler, and therfore more dense than the surrounding aesthensphere

Question 30

can the age of the earth be relaibly estimated from sediment thickness?

Answer 30

no - much of earths history is prepresented by uncomformities between strata rather than strata themselves

Question 31

If a P-wave is traveling through sandstone and then encounters peridotite, the P-wave will …?

Answer 31

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.

Question 32

example of a coninental volcaninc arc?

Answer 32

the Andes

Question 33

If an S-wave is traveling through rock when it encounters a magma chamber, the S-wave will…?

Answer 33

not travel through the magma

Question 34

where is most of the PUSHING force driving plate motion produced?

Answer 34

at mid ocean ridges

Question 35

at at subduction zone, is the overriding plate oceanic or continental lithosphere?

Answer 35

may be both