Plate tectonics

Question 1

How old is the earth?

Answer 1

Over 4.5 billion years old

Question 2

Name the structure of the earth in order from exterior to the centre

Answer 2

Crust- oceanic and continental
Mantle or asthenosphere
Outer core
Inner core

Question 3

Name the characteristics of the crust

Answer 3

• 0-70km thick, coolest and least dense rock
• rocks are rich in sodium, silicon, aluminium and potassium
• it’s divided into continental crust and oceanic crust

Question 4

What are the properties of continental crust?

Answer 4

• it’s old, over 1500 million years old
• it’s permanent
• less dense
• mainly granite, silicon, aluminium and oxygen

Question 5

What are the properties of oceanic crust?

Answer 5

• younger, less than 200 million years old
• it is created so it can be destroyed
• 6-10km thick and is denser so it can sink
• mainly basalt silicon magnesium and oxygen

Question 6

What are the properties of the mantle?

Answer 6

• 2900km thick
• apart from the rigid upper mantle, most of the mantle is semi molten containing lighter elements of silicon and oxygen
• temperatures reach 5,000 degrees C and generate convection currents

Question 7

What are the properties of the core (inner and outer)?

Answer 7

• hottest part of the earth, over 5,000 degrees C
• outer part is liquid and the inner is solid
• the inner is made from iron and nickel ore

Question 8

What is the name of the discontinuity found at the top of the mantle?

Answer 8

Mohorovicic boundary

Question 9

What does the mohorovicic boundary do?

Answer 9

Separates the mantle from the crust

Question 10

The crust and part of the mantle beneath form…

Answer 10

Large plate like areas of the lithosphere which float upon the soft and ductile material known and the asthenosphere

Question 11

What are the crust and the upper most part of the mantle?

Answer 11

A single unit

Question 12

What are the two processes that heat from the core is produced?

Answer 12

• Primordial heat left over from the earths creation

- Radiogenic heat produced by the radioactive decay of isotopes

Question 13

What isotopes contribute to the radioactive decay?

Answer 13

Uranium -238
Thorium- 232
Potassium-40

Question 14

What does the theory of plate tectonics help us understand?

Answer 14

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

Question 15

How many plates is the earth made up of?

Answer 15

16

Question 16

Do plates move? If so, how much?

Answer 16

Yes, a few centimetres per year