The Earth's structure is responsible for tectonic hazards

Question 1

What is the core?

Answer 1

Made up of dense rock containing iron and nickel alloys and is divided into a solid inner core and a molten outer one

Question 2

How hot is the core?

Answer 2

Over 5000 degrees

Question 3

How is the heat produced in the core?

Answer 3

Primordial heat left over from the earth’s formation

Radiogenic heat produced by the radioactive decay of isotopes

Question 4

What is the mantle?

Answer 4

Made up of molten and semi-molten rocks containing lighter elements such a silicon and oxygen

Question 5

What is the crust?

Answer 5

Even lighter than the mantle

Made of silicon, oxygen, aluminium, potassium and sodium

Question 6

How thick is the crust under the ocean?

Answer 6

6-10km thick

Question 7

How thick is the crust under the continents?

Answer 7

30-40km thick

Question 8

How thick is the crust under the highest mountain ranges?

Answer 8

70km thick

Question 9

What has new research suggested about the upper mantle and the crust?

Answer 9

It should be divided into the lithosphere and asthenosphere

Question 10

What is the lithosphere?

Answer 10

Consists of the crust and the rigid upper section of the mantle

Question 11

How thick is the lithosphere?

Answer 11

80-90km thick

Question 12

Why is the lithosphere important?

Answer 12

It is divided into seven very large plates and a number of smaller ones

Question 13

What are the seven plates in the lithosphere divided into?

Answer 13

Two categories - oceanic and continental

Question 14

What is the asthenosphere?

Answer 14

Lies beneath the lithosphere and it semi-molten on which the plates float and move

Question 15

What theory did Alfred Wegener publish in 1912?

Answer 15

The theory that a single continent existed about 300 million years ago called Pangea

Question 16

What did Wegener theory state?

Answer 16

That the super continent (Pangea) had split into the two continents, where the two continents split again to form today’s continents

Question 17

What were the two original continents after Pangea split in two?

Answer 17

Laurasia in the north and Godwanaland in the south

Question 18

What Geological evident support Wegener’s theory?

Answer 18

Rock sequences in northern Scotland closely agreed with those found in Canada - must have been joined
Evidence of late-Carboniferous glaciation deposists found in South America, Antartica and India - must have been joined

Question 19

What Biological evidence supports Wegener’s theory?

Answer 19

Fossil brachiopods found in Indian limestone are comparable with similar fossils in Australia
Fossil remains of the Mesosauras are found in South America and Southern Africa

Question 20

What is ridge push?

Answer 20

Heating of rock - The hot molten magma that rises at a mid-ocean ridge heats the rocks around it.
Heated and expansion - As the asthenosphere and lithosphere at the ridge are heated, they expand and become elevated above the surrounding sea floor. This elevation produces a slope down and away from the ridge.
Rock cools and gravity causes the rock to slide away from ridge - However, as the newly formed rock ages and cools, it becomes more dense. Gravity then causes this older, denser lithosphere to slide away from the ridge, down the sloping asthenosphere.
Process happens again - As the older, denser lithosphere slides away, new molten magma wells up at the mid-ocean ridge, eventually becoming new lithosphere.

Question 21

What is gravitational sliding?

Answer 21

The same thing as ridge push

Question 22

What is convection?

Answer 22

Circulation of material caused by differences in density - less dense rises, more dense sinks

Question 23

How do convection currents work?

Answer 23

Hot mantle rises upwards and comes into contact with Earth’s crust
As that material grows further apart from its heat source, it cools and therefore becomes more dense
It then sinks, forming a convection current

Question 24

What drives convection?

Answer 24

The source of heat for convection currents are radioactive materials found in the Earth’s core

Question 25

How does convection cause plate tectonics?

Answer 25

The motion of convection inside the earth, we see the same motion on the surface of the earth. This motion is connected to two processes

Question 26

What is a divergent plate margin?

Answer 26

A tectonic boundary where two plates are moving away from each other and new crust is forming from magma that rises to the Earth's surface between the two plates

Question 27

What do oceanic divergent plate margins commonly form?

Answer 27

mid-ocean ridge, volcanic islands (which form as the plates move apart and a gap is produced, which molten lava rises to fill)

Question 28

What happens at a continental divergent plate margin?

Answer 28

Continental plate is arched upwards from the convection current's lift, pulled thin by extensional forces, and fractured into a rift-shaped structure. As the two plates pull apart, normal faults develop on both sides of the rift, and the central blocks slide downwards.

Question 29

What do continental divergent plate margins commonly form?

Answer 29

Rift valleys, and Earthquakes occur as a result of this fracturing and movement

Question 30

What is slab pull?

Answer 30

At a subduction boundary, one plate is denser and heavier than the other plate. The denser, heavier plate begins to subduct beneath the plate that is less dense. The edge of the subducting plate is much colder and heavier than the mantle, so it continues to sink, pulling the rest of the plate along with it. The force that the sinking edge of the plate exerts on the rest of the plate is called slab pull.