Structure of the Earth - physical

Question 1

how is the Earth structured?

Answer 1

inner core
outer core
mantle
crust

Question 2

what is the inner core?

Answer 2

solid, dense ball of metal - mainly composed of iron and nickel
radius of 1200 km
temperatures thought to be over 6000°C

Question 3

what is the outer core?

Answer 3

composed of iron and nickel - melted by the inner core
radius of 2200 km
temperatures between 4000 and 5000°C

Question 4

what is the mantle?

Answer 4

thickest layer of the Earth - 2900 km
makes up 85% of the earths volume
on average 3000°C
bottom part is called the asthenosphere 

Question 5

what is the crust?

Answer 5

outer layer of the earth
two crusts: oceanic and continental
oceanic = 6 km thick
continental = 35 km thick

Question 6

what are convection currents?

Answer 6

the earth’s hot core heats up the lower mantle magma which rises towards the lithosphere
as it hits the underside of the lithosphere, it is dragged along it
this pressure carries the tectonic plates along and makes them move
limited evidence

Question 7

what is ridge push?

Answer 7

occurs at mid ocean ridges - associated with constructive plate boundaries
magma rises to surface, heating surrounding rocks which then expand and become elevated above the sea floor, forming a slope
a new rock forms which slides down, causing seafloor spreading and plates move apart

Question 8

what is slab pull?

Answer 8

at a destructive plate boundary
the subducting oceanic plate is denser than the surrounding material
as the plate begins to sink into the mantle it pulls the rest of the plate behind it

Question 9

what is sea floor spreading?

Answer 9

occurs at the boundaries of tectonic plates
plates move apart and create an ocean floor

Question 10

what is the theory of continental drift?

Answer 10

all of the continents used to be joined together in one large landmass before they split apart and drifted into their current positions
continental drift is the movement of lithospheric plates believed to be caused by the radioactive decay of elements in the core 

Question 11

what is biological evidence of continental drift?

Answer 11

mesosaur
small freshwater dinosaur found in brazil and west africa - too small to have swam that distance
prehistoric ferns
found in coal in antarctica and india - exactly the same & dated back to the same time

Question 12

what is geological evidence of continental drift?

Answer 12

igneous rock
found in south america and on the west african coast
sedimentary rock
same composition & make-up found in west scotland and east canada

Question 13

what are the four types of plate boundary?

Answer 13

constructive
collision
destructive
conservative

Question 14

what are constructive plate boundaries?

Answer 14

plates move apart & magma fills the gap - new land is created
eg - mid atlantic ridge and iceland
on land: plates move apart, collapse in on each other & magma cannot rise up - creates a rift valley eg - east african rift valley
this can fall below sea level, creating a new ocean - mid ocean ridge

Question 15

what are collision plate boundaries?

Answer 15

two continental plates meet - one cannot subduct the other as they are both very thick
causes them to buckle and form fold mountains
eg - indian plate + eurasian plate = himalayas

Question 16

what are destructive plate boundaries?

Answer 16

denser oceanic crust meets lighter continental crust
oceanic subducts continental & creates deep sea trench and volcanoes
two oceanic crusts meet - creates island arcs
one plate subducts the other, magma rises & creates submarine volcanoes
arcs of volcanic islands are made eg - caribbean islands

Question 17

what are conservative plate boundaries?

Answer 17

plates move past each other in separate directions / same directions but different speeds movement is not smooth creating tension and pressure
pressure is released a shallow focus earthquakes
eg - north american plate + pacific plate = san andreas fault