theory of plate tectonics

Question 1

core characteristics

Answer 1

made of dense rock - iron and nickel

inner core - solid

outer core - molten

temperature - more than 5000 degrees - primordial heat + radioactive heat

Question 2

mantle characteristics

Answer 2

molten/semi molten

contains silicon and oxygen

Question 3

crust characteristics

Answer 3

solid

contains - oxygen, aluminium, silicon + sodium

varies in thickness

continental - 30-40km deep

ocean - 6-10km deep

Question 4

lithosphere

Answer 4

contains curst and upper mantle

80 km - 90 km deep

divided into different tectonic plates

Question 5

asthenosphere

Answer 5

molten/semi molten

tectonic plates float on asthenosphere

below lithosphere

Question 6

continental crust plates

Answer 6

thickness - 30km-70km

age - 1,500 million + years

density - 2.6 - lighter

composition - granite, silicon, aluminium and oxygen

Question 7

ocean crust plates

Answer 7

thickness - 6km-10km

age - >200 million years

density - 3.0 - heavier

composition - basalt, silicon, magnesium and oxygen

Question 8

which crust is denser oceanic or continental

Answer 8

oceanic - 3.0

Question 9

which crust is thicker oceanic or continental

Answer 9

continental - 30 - 70km

Question 10

who came up with the theory

Answer 10

Alfred Wegener

Question 11

what was the world structure originally

Answer 11

PANGEA - supercontinent

Question 12

7 main plates

Answer 12

pacific
North American 
South American 
african 
eurasian 
australian 
antartic

Question 13

smaller plates (4)

Answer 13

nazca plate

Caribbean plate

indian plate

arabian plate

Question 14

geological evidence of continental drift

Answer 14

fit of continents - like a puzzle - South American coast fits into African west coast

glacial deposits - glacial scars - 290 million years ago - found in South America and India

same rocks sequences found in Scotland and eastern Canada

Question 15

biological evidence of continental drift

Answer 15

mesosaurus fossils - South Africa + South America - ocean between

plant fossils found in India and Antartica

Question 16

sea floor spreading

Answer 16

mid Atlantic ridge - crust either side suggested sea floor spreading

molten material rising from mantle - forming new material in the middle - pushing plates apart

the further away from the ridge the older the crust

Question 17

how does sea floor spreading link to alternating polarity

Answer 17

earth magnetic field switches every 400,000 years

field switches from the North Pole to the South Pole - molten material that solidifies to form ocean crust contains iron particles - attracted to magnetic field - when field is north the particles attract to north

alternating bands due to alternating polarity - therefore crust is spreading overtime as new crust is formed sand pushed out

Question 18

what are ocean ridges and how are they formed

Answer 18

occur at contructive plate boundaries - plates moving away from each other

lava rises to form a ridge

can for underwater volcanoes

such as the mid Atlantic ridge

Question 19

what are rift valleys

Answer 19

happen on continual plates - at destructive boundaries

when the plates move apart and area of land in the middle sinks

causing a valley to form

East African rift valley

Question 20

what are deep sea trenches

Answer 20

occur at destructive plate boundaries

oceanic plate subduct due to higher density

when it sinks it melts into mantle

example - Marianas trench

Question 21

what is the Benioff zone

Answer 21

where the oceanic plate melts during subduction

Question 22

what is a fold mountain

Answer 22

occurs at destructive plater boundaries

continental - continental

similar densities - pushed up wards - forms mountain ranges

Himalayas - Everest - Indian and eurasian plate