Layers of the Earth

Question 1

What is gravitational differentiation?

Answer 1

Shortly after the Earth formed while it was still molten, the heavier materials sank to form the core while the lighter materials rose to form the crust.

Question 2

What is the Earth’s crust?

Answer 2

A thin, cool, rigid layer at the Earth’s surface. Most of the rocks are calcium and aluminum silicates.

Question 3

What is the mantle?

Answer 3

A thick, molten layer of the Earth. Most of the rocks are magnesium and iron silicates.

Question 4

What is the Outer Core?

Answer 4

A liquid layer composed mainly of iron and nickel.

Question 5

What is the Inner Core?

Answer 5

The solid center of the Earth composed mainly of iron.

Question 6

What is the lithosphere?

Answer 6

The outer layer of the Earth by physical properties. It is the rigid part of the crust and upper mantle. It is broken into pieces called plates.

Question 7

What is the asthenosphere?

Answer 7

A deformable layer below the lithosphere. Convection currents in this layer are theorized to help move the lithosphere’s plates.

Question 8

What is the mesosphere?

Answer 8

The middle of the five layers of the Earth. It is a hot but solid layer because of the pressure of the overlying layers.

Question 9

What is a fault?

Answer 9

A fracture along which the blocks of crust on either side have moved.

Question 10

What are characteristics of a P-wave?

Answer 10

A P-wave is a compression wave formed in an earthquake. Compression waves move particles parallel to the direction of energy transfer. It is the fastest of the seismic waves, and it can travel through both solids and liquids.

Question 11

What are the characteristics of an S-wave?

Answer 11

An S-wave is a transverse wave, where particles move at right angles to the direction of energy transfer. It is slower than a P-wave. It can travel through solids but not through liquids.

Question 12

What is a seismograph?

Answer 12

An instrument that detects seismic waves.

Question 13

What is an earthquake hypocenter?

Answer 13

Also called an earthquake focus, it is the location where the rocks break and energy is released.

Question 14

What is an earthquake epicenter?

Answer 14

It is the location on the Earth’s surface above where the earthquake occurred.

Question 15

What is the shadow zone associated with an earthquake.

Answer 15

It is an area on the Earth’s surface where seismographs do not detect earthquake waves. Shadow zones form because P and S waves change speed and direction when they enter a different layer of the Earth with different physical properties. S-waves do not travel through the liquid outer core.

Question 16

How does energy transfer by radiation?

Answer 16

Photons of energy travel by waves.

Question 17

How does energy transfer by conduction?

Answer 17

Energy moves through substances in contact because of particle collisions.

Question 18

How does energy transfer by convection?

Answer 18

Energy moves within a substance by density differences.

Question 19

What is a convection current?

Answer 19

Movement of a fluid when warm, less dense material rises and cool, more dense material sinks.

Question 20

What information does a seismograph detect?

Answer 20

Seismographs detect the arrival times of P-waves and S-waves.

Question 21

What does the difference in arrival times between the P-wave and S-wave indicate about the location of the seismograph to the earthquake?

Answer 21

The shorter the separation time between the P-wave arrival and the S-wave arrival indicates the closer the seismograph is to the earthquake.

Question 22

How many seismograph readings are needed to determine the epicenter of an earthquake?

Answer 22

Three readings are the minimum needed to pinpoint a single epicenter.

Question 23

What are the two sources of heat in Earth’s interior?

Answer 23

Heat leftover from the formation of the Earth and heat generated by the radioactive decay of certain elements.

Question 24

Why do scientists believe that heat transfer within the Earth layers does not occur by radiation or conduction?

Answer 24

Radiation isn’t really possible through solid rock, and conduction is really slow.

Question 25

What is plate tectonic theory?

Answer 25

The rigid outer part of the Earth is broken into tectonic plates that are in constant motion.

Question 26

How do scientists think earthquakes occur?

Answer 26

Slowly moving plates apply stress to the rock layers. When the elastic limit of the rocks is exceeded, the energy is released as an earthquake.

Question 27

How does the temperature of the layers change from the crust to the core?

Answer 27

The temperature of the layers increases as one moves from the crust to the core.

Question 28

How does the pressure on the layers change from the crust to the core?

Answer 28

The pressure on the layers increases as one moves from the crust to the core.