C2A - The Earths Structure

Question 0

Describe the crust ?

Answer 0

A thin outer layer of solid rock. Average depth is 20 km

Question 1

What is the earth made up of ?

Answer 1

A crust 
A mantle 
A outer core 
A Inner core 
Lithosphere

Question 2

Describe the mantle ?

Answer 2

The solid section between the crust and the core. Near the crust it’s very rigid but as you go deeper the temperature rises so becomes less rigid and flows very slowly. Basically like a semi liquid

Question 3

What percentage of the earths radius is the core ?

Answer 3

Just over half

Question 4

What is the difference between the outer and inner core ?

Answer 4

Outer core = liquid

Inner core = solid

Question 5

What does the lithosphere include ?

Answer 5

It includes the crust and upper mantle

Question 6

What is the lithosphere made up of ?

Answer 6

A jigsaw of tectonic plates

Question 7

Three properties of the lithosphere ?

Answer 7

1) cold
2) rigid
3) 100 km thick

Question 8

Why is it so hot inside the earth ?

Answer 8

Radioactive decay

Question 9

Describe convection currents in the mantle

Answer 9

The heat from radioactive decay creates the convection currents in the mantle causing the plates to move

Question 10

What are big rocky rafts that float on the mantle ?

Answer 10

Tectonic plates

Question 11

How are tectonic plants able to float on the mantle ?

Answer 11

They are less dense than the mantle

Question 12

What happens if tectonic plates all moved ?

Answer 12

The continents will move too

Question 13

Jane is worried her continent will float away from her boyfriends in the next week. Tim reassures her that that won’t happen. How does he know ?

Answer 13

The plates move very very slowly. About 2.5cm a year

Question 14

How do earthquakes and volcanos occur ?

Answer 14

When plates meet

Question 15

Why is it difficult to study the inner structure of the earth ?

Answer 15

You can’t get at it directly as the crust is too thick to drill through

Question 16

What do scientists use to study the earths structure ?

Answer 16

Seismic waves

Question 17

How are seismic waves produced ?

Answer 17

By earthquakes. Or setting of a man made explosion at the earths surface

Question 18

How do seismic waves help ?

Answer 18

By measuring the time it takes for the waves to travel through the earth and the location of them scientists can draw conclusions about the earths structure

Question 19

Name the two types of seismic wave that can travel through earth ?

Answer 19

P waves

S waves

Question 20

What are the similarities and differences between p and S waves ?

Answer 20

Both travel through solids. But only P can travel through liquid

Question 21

If S waves are detected in the mantle but not the outer core what does that tell us ?

Answer 21

Mantle is a solid whereas outer core must be a liquid

Question 22

Scientists realised the inner core was solid. How ?

Answer 22

P waves travel faster through the middle of the core

Question 23

A long time ago every was confused about the formation of the earth as observations had not been explained. What things confused them ?

Answer 23

1) the fact that fossils of very similar plants and animals had been found on different sides of the Atlantic Ocean
2) why the coast lines of Africa and America fit together
3) why there were fossils of sea creatures in the Alps

Question 24

Explain the ‘land bridge’ idea

Answer 24

Many people thought continents had been linked by land bridges which had now sunk or been covered by water as the earth cooled

Question 25

What was Alfred wegeners initial idea ?

Answer 25

Africa and South America had originally been one big continent that split in half

Question 26

What was wegeners evidence ?

Answer 26

There were matching layers in the rocks in the different continents and similar earthworms were living in both

Question 27

What is the modern day plate tectonics theory ?

Answer 27

1) 300 million years ago there was a super continent that was called Pangea
2) Pangea broke into smaller chunks. Those are our continents
3) These chunks are still slowly drifting apart

Question 28

Why did other scientists frown upon Wegeners theory ?

Answer 28

1) He said mountains were formed by continents crashing into each other
2) Drifting explanation was not clear
3) He said continents movement was caused by tidal forces and earths rotation

Question 29

Later on more evidence was found that explains the sea floor movement. What was it ?

Answer 29

Magma rises up through the sea floor. Solidifies and forms underwater mountains which are kind of symmetrical. Suggesting the seafood spreads about 10 cm a year.

Question 30

Explain the magnetic orientation evidence ?

Answer 30

Liquid magma erupts out of the gap and iron particles in the rocks tend to align themselves with the earths magnetic field. As it cools they set in position

Every half million years or so the earths magnetic field swaps direction and the Rock on either side of the ridge has bands of alternate magnetic polarity, symmetrical about the ridge