Plate Tectonics

Question 1

What is the continental drift theory

Answer 1

Introduced by Alfred Wegener in 1912

At one point in time all the continents were joined together in a super continent -> Pangaea

Continents drifted away over millions of years

Unable to identify what caused the movements

Theory is now widely accepted

Question 2

What are the 7 main plates

Answer 2

Eurasian plate

African plate

South American plate

North American plate

Antarctic plate

Pacific plate

Nazca plate

Question 3

What is earths structure

Answer 3

Crust

Mantle

Outer core

Inner core

Question 4

What is the crust

Answer 4

Two types of

Oceanic crust
- greater density
- 7km thick
- 200 million years old
- mainly basalt

Continental crust
- less dense
- 70km thick on average
- 4.4 billion years old
- mainly granite

Question 5

What is the mantle

Answer 5

• 3000 km thick

Mainly solid rock

Question 6

What is the outer core

Answer 6

• 2200km thick
• mostly liquid iron and nickel
• generates the earths magnetic field

Question 7

What is the inner core

Answer 7

• 1300 km thick
• solid iron and nickel

Question 8

How does a you hold mountain form

Answer 8

Forms when two plates meet at a convergent margin

Continental and oceanic plate are pushed together

Denser oceanic crust is pushed underneath the continental crust

Causes the uplift of the continental crust

Question 9

How does a rift valley form

Answer 9

Plates move apart at a divergent plate margin

This causes areas of the crust to drop

Leaves a depression in the floor -> known as valley

Question 10

How does a ocean ridge form

Answer 10

Plates move apart at divergent margins, which creates a gap in the earth

Magmas rises pushing through the gap, creating an underwater volcano

Magma solidifies creating new layers of oceanic crust that build up over time

Question 11

How does a deep sea trench form

Answer 11

Form when the denser plate is pushed beneath the lighter plate into the mantle

Downwarding of the the ice sic plate causes tench

Question 12

How is an island arc formed

Answer 12

Subduction of oceanic plate under continental

Subduction g plate melts into the mantle in the asthenosphere

Some debris comes to the surface to form a volcano

Question 13

How does a volcano form

Answer 13

Forms when molten rock reaches the earths crust

Pressure builds

Burst out

Magma cools and solidifies

Over many years builds up after multiple eruptions

Question 14

What is a magma plume

Answer 14

Plumes rise through the mantle

Begin to melt in shallow depths of the asthenosphere by decompression melting

This creates large volumes of magma

Rises to the surface and erupts from hotspots

Can erupt anywhere.