Plate tectonics

Question 1

how old is the earth?

Answer 1

over 4.5 billion years old

Question 2

what are the characteristics of the crust?

Answer 2

0-70km thick
coolest and least dense rocks
the rocks are rich in sodium, silicon, aliminium and potassium

Question 3

what can the crust be divided into?

Answer 3

continental crust and oceanic crust

Question 4

what are the characteristics of the continental crust?

Answer 4

its old
permanent
less dense

Question 5

what are the characteristics of oceanic crust?

Answer 5

is young
can be created and destroyed
6-10 km thick
denser than continental crust

Question 6

what are the characteristics of the mantle?

Answer 6

2900km thick
semi-molten rock
temperatures near core reach 5000 degrees
high temps generate convection currents

Question 7

what are the characteristics of the core?

Answer 7

hottest part of the earth
over 5000 degrees
outer part is liquid
inner part is solid 
made from iron and nickle ore

Question 8

what separates the mantle from the crust?

Answer 8

the mohorovicic boundary

Question 9

the heat in the core is produced at a result of what 2 processes?

Answer 9

primordial heat

radiogenic heat

Question 10

what is primordial heat?

Answer 10

left over heat from the earth’s formation

Question 11

what is radiogenic heat?

Answer 11

produced by the radioactive decay of isotopes

Question 12

what has the theory of plate tectonics helped us to understand?

Answer 12

• the distribution of the worlds major landforms
• where natural hazards can strike
• the distribution of minerals and energy supplies

Question 13

how do tectonic plates move?

Answer 13

convection currents

Question 14

how do convection currents work?

Answer 14

heat is obtained by radioactive decay
hot air/liquid rises as it is less dense
cool air sinks as it is more dense

Question 15

what is the hotspot theory?

Answer 15

wilson noted that in certain locations around the world volcanism has been active for very long periods of time
this could only happen if very small long lasting exceptionally hot regions called hotspots existed below the surface

Question 16

how are hotspots formed?

Answer 16

radioactive decay within the core generates very hot temperatures.
if the decay is concentrated hot spots will form around the core
these hotspots heat the lower mantle creating localised thermal currents where magma plumes rise vertically

Question 17

what did wilson suggest about continuing plate movement?

Answer 17

Continuing plate movement eventually carries the island beyond the hotspot cutting it off from the magma source
as one island volcano becomes extinct another develops over the hotspot