Earth Structure

Question 1

What are the main layers of the Earth?

Answer 1

• Crust
• Mantle
• Core

These layers can be derived from seismic waves.

Question 2

The crust of the Earth is between _______ and _______ km thick.

Answer 2

5 and 80

The crust is the uppermost layer of the Earth.

Question 3

What are the two types of crust?

Answer 3

• Continental crust
• Oceanic crust

Oceanic crust is thinner and made up of basalt, while continental crust is thicker and heterogeneous.

Question 4

The mantle lies beneath the crust with a depth of about _______ km.

Answer 4

2900

The mantle has many layers within the upper and lower mantle.

Question 5

What are the two layers of the core?

Answer 5

• Inner core
• Outer core

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

Question 6

What is the composition of the Earth’s core primarily made up of?

Answer 6

• Iron
• Nickel
• Sulfur
• Other minor elements

The density is greater in the outer core than in the inner core.

Question 7

The upper layer of the mantle is known as the _______.

Answer 7

Lithosphere

Below the lithosphere is the asthenosphere.

Question 8

What are the two sources of heat generation within the Earth?

Answer 8

• Primordial heat sources
• Thermal energy from radioactive decay

Different crustal compositions have different isotopes dominant in them.

Question 9

What are the three key processes of heat flow?

Answer 9

• Conduction
• Convection
• Radiation

These processes determine the distribution of temperature within the Earth.

Question 10

True or false: Seismic waves provide direct measurement of the Earth’s internal structure.

Answer 10

FALSE

Indirect methods using seismological techniques are necessary for measurement.

Question 11

What type of waves do P waves represent?

Answer 11

Waves that transmit through both solid and liquid

P waves are fast and direct.

Question 12

What type of waves do S waves represent?

Answer 12

Waves that transmit through solids

S waves are slower than P waves.

Question 13

What is seismic tomography used for?

Answer 13

• Deriving 3D images of the Earth’s structure
• Identifying heterogeneity in the Earth
• Understanding plate tectonics

It integrates travel time of seismic waves and properties of the medium.

Question 14

Define lithosphere.

Answer 14

Solid outer part of the Earth

It includes the crust and the uppermost part of the mantle.

Question 15

Define heterogeneous.

Answer 15

A rock or formation with varying physical and chemical properties

This contrasts with homogeneous formations.

Question 16

What does Fourier’s law describe?

Answer 16

Heat conduction through rocks and minerals

It is a fundamental principle in geophysics.

Question 17

Define asthenosphere.

Answer 17

Zone of Earth’s mantle lying beneath the lithosphere

It is more hot and fluid, allowing convection to occur.

Question 18

What is a transition layer?

Answer 18

A zone where there is a gradual change in rock properties or structure

This occurs between the upper and lower mantle.

Question 19

Define elastic deformation.

Answer 19

Temporary, reversible change in a rock’s shape or volume when stress is applied

It is a key concept in understanding how materials respond to forces.

Question 20

What is tomography in the context of geophysics?

Answer 20

An imaging technique that creates cross-sectional images of Earth’s subsurface

It helps visualize the internal structure of the Earth.