Structure of the earth

Question 1

Describe the structure of the Earth

Answer 1

a sphere with a thin rocky crust, a mantle and an iron core

Question 2

Recall that the movement of tectonic plates is very

slow

Answer 2

2.5cm per year

Question 3

Describe magma

Answer 3

molten rock beneath the surface of the Earth

Question 4

describe lavca

Answer 4

molten rock at the Earth’s surface

Question 5

Explain why some people choose to live near

volcanoes

Answer 5

lava forms very fertile soil

Question 6

Describe the lithosphere

Answer 6

the (relatively) cold rigid outer part of the Earth that includes the crust and part of the mantle

Question 7

Explain the problems associated with studying the

structure of the Earth

Answer 7

• crust is too thick to drill through
• the need to use seismic waves produced by
earthquakes or man-made explosions

Question 8

what is the lithosphere made of?

Answer 8

tectonic plates that are less dense than the mantle below

Question 9

Explain why the theory of plate tectonics is now

widely accepted

Answer 9

• it explains a wide range of evidence
• it has been discussed and tested by a wide range
of scientists

Question 10

Describe the mantle

Answer 10

it’s the zone between the crust and the core which is:
• cold and rigid just below the crust
• hot and non-rigid at greater depths and therefore
able to move.

Question 11

Describe the theory of plate tectonics

Answer 11

• energy transfer involving convection currents in
the semi-rigid mantle causing the plates to move
slowly
• oceanic crust more dense than continental crust
• collision between oceanic plate and continental
plate leads to subduction and partial melting
• plates cooler at ocean margins so sink and pull
plates down.

Question 12

Describe in simple terms the development of the

theory of plate tectonics

Answer 12

• Wegener’s continental drift theory (1914)
• continental drift theory not accepted by scientists
at the time
• new evidence in 1960s – sea floor spreading
• theory of plate tectonics slowly accepted by the
scientific community as subsequent research has
supported the theory.

Question 13

Describe different types of igneous rocks that are

formed from lava

Answer 13

• iron-rich basalt is formed from runny lava from a
fairly safe volcanic eruption
• silica-rich rhyolite is formed from thick lava from
an explosive eruption

Question 14

Explain why geologists study volcanoes

Answer 14

• to be able to forecast future eruptions
• to reveal information about the structure of the
Earth

Question 15

what does the type of volcanic eruption

depend on?

Answer 15

the composition of the magma