C2 - Earths Structure & Plate Tectonics Flashcards Preview

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Flashcards in C2 - Earths Structure & Plate Tectonics Deck (28)
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1
Q

What is the crust?

A

The crust is the Earth’s thin outer layer of solid rock, on average its depth is 20km

2
Q

What is the lithosphere?

A

The lithosphere is a shell of sorts, it includes the crust and upper part of the mantle, it is made up of a “jigsaw” of tectonic plates, the lithosphere is cold and rigid.

3
Q

What is the mantle?

A

The mantle is the solid section between the crust and the core, it is very rigid near the crust.

4
Q

Describe the mantle.

A

The mantle is very rigid near the crust, as you go deeper into the mantle its temperature increases and becomes less rigid, it behaves like a semi liquid and flows.

5
Q

Describe the core.

A

The Earth’s core covers just over half of the Earth’s radius.

6
Q

Describe the difference between the inner core and the outer core.

A

The inner core is solid, whereas the outer core is liquid.

7
Q

What creates heat inside the Earth?

A

Radioactive decay creates a lot of the heat in the Earth.

8
Q

What causes the tectonic plates in the lithosphere to move?

A

The heat coming from radioactive decay creates convection currents in the mantle, this will cause the plates of the lithosphere to move.

9
Q

What are tectonic plates?

A

Tectonic plates are essentially big rocky rafts that float on the mantle, however they are less dense than the mantle.

10
Q

How fast do tectonic plates move?

A

Tectonic plates move very slow, they move at a speed of 2.5 cm per year.

11
Q

What happens when two plates meet?

A

When two tectonic plates meet it will often result in a volcano or an earthquake, these occur because of the movement of plates against each other.

12
Q

Why is it difficult to study the structure of the Earth?

A

It is difficult to study the inner structure of the earth because the crust is thick to drill through.

13
Q

How do scientists study the Earth’s structure?

A

Scientists use seismic waves in order to study the Earth’s structure, they measure the time that it takes for these waves to travel through the Earth, and then where the waves are detected, using this the scientists can draw conclusions about the Earth’s structure.

14
Q

Why do earthquakes happen?

A

Earthquakes happen when large parts of the Earth’s crust and upper mantle move suddenly. It’s difficult to predict exactly when and where an earthquake will happen, even when a lot of data is available.

15
Q

How can you detect seismic waves?

A

Seismic waves can be detected using seismographs.

16
Q

How are seismic waves produced?

A

Earthquakes can produce shock waves called seismic waves, however large man made explosions on the Earth’s surface can produce seismic waves.

17
Q

What are the two types of seismic wave?

A

The two types of seismic wave are P and S waves.

18
Q

What the properties of the two types of seismic wave?

A

P - Waves :
P waves can travel through solids and liquids, and they are relatively faster than S waves.
S - Waves:
S waves are transverse and travel relatively slower than P waves, and they can only travel through Solids.

19
Q

How do we know the mantle is solid?

A

S waves can travel through the mantle, this indicates to scientists that the mantle is solid.

20
Q

How do we know the Earth’s outer core is liquid?

A

S waves are not detected in the core’s shadow, therefore the outer core must be liquid.

21
Q

How do we know the Earth’s inner core is solid?

A

P waves travel must faster through the middle of the core, this tells us that the inner core must be solid.

22
Q

What is a seismometer?

A

A seismometer is a piece of equipment that picks up vibrations in the earth.

23
Q

What was Alfred Wegener’s hypothesis in 1914 about South America and Africa?

A

Alfred Wegener hypothesized that Africa and South America had previously been one continent which had then split, however he required more evidence to prove this theory.

24
Q

What was Alfred Wegener’s evidence to support his theory?

A

Wegener found matching layers in the rocks on different continent, he also found similar earthworms living in both South America and South Africa.

25
Q

What was Wegener’s continental drift theory?

A

The continental drift theory supposed that 300 million years ago there had been one super continent called “Pangaea”, this continent would break into smaller chunks that would drift away, these smaller chunks would make up the modern day continents.

26
Q

Why was Wegener’s theory not accepted at first?

A

Wegener’s theory was not accepted because this opposed the “land bridge” theory, many scientists were hostile towards Wegener’s theory because he was able to explain many things that the “Land bridge” theory was not able to such as the formation of mountains.
Movement from tectonic plates was not detectable, therefore many geologists refused to believe that continents could move.

27
Q

Why does magma rise up through the sea floor?

A

Magma is less dense than the crust, because of this it can rise to the surface when two tectonic plates meet, this forms a volcano.

28
Q

How are mountains formed?

A

Where tectonic plates meet, the Earth’s crust becomes unstable as the plates push against each other, or ride under or over each other the crust may ‘crumple’ to form mountain ranges..