Week 3: Earth and its Interior

Question 1

How long ago did Earth form?

Answer 1

4.6 x 10^9 years ago (4,600,000,000 years ago)

Question 2

What is the “Giant Impact Theory”?

Answer 2

The moon was created through a collision between Earth and Theia

Question 3

Be able to discuss the three main layers of the rocks on the Earth’s crust.

Answer 3

-Core
Most dense part of the interior

-Mantle
Less dense than the core

-Crust
Least dense layer

Question 4

What are the two most common types of rocks on the Earth’s crust? What types of crust do you find these rocks in?

Answer 4

Basalt (55% of Earth’s surface)
Found in oceanic crust
Granite (45% of Earth’s surface)
Found in continental crust

Question 5

How large is the mantle compared to other layers of the earth?

Answer 5

Ranges from 35km to 2890km

Largest portion of the Earth’s interior

Question 6

What is convection?

Answer 6

The transfer of thermal energy (heat) by the movement of fluid

Question 7

What effect does the convection currents have on the crust of the earth?

Answer 7

Convergent - towards
Divergent - away
Transform - slide past

Question 8

What are the main differences between the inner and outer core of the earth?

Answer 8

• The inner core is mostly solid iron and nickel due to extreme pressures
• The outer core is molten which means it is able to flow as a liquid

Question 9

What is differentiation? If an object is differentiated (has layers), what does that imply about the object’s early history?

Answer 9

Differentiation is the process of denser materials separating out from lighter materials

This implies that the materials are free to move around

Question 10

How do you measure the age of the planet/Moon/Asteroid?

Answer 10

• Counting Craters
• Radioactivity

Overtime, some atoms spontaneously split (decay) into smaller atoms

This creates two new atoms and releases energy

Question 11

What is a half life? How do we use us to measure ages?

Answer 11

It is the time it takes for about half of the sample to decay from the original into a new type of atom

Used to measure ages through radioactivity (explained in the question before)

Question 12

Be able to describe in detail what a liquid dynamo is, and how it generates a magnetic field on earth.

Answer 12

Liquid dynamo is when the outer core is molten and liquid is able to flow

This helps to produce Earth’s magnetic field

A liquid outer core means that it also has convection currents within it
-These create loops

Question 13

What are the three ways we study Earth’s interior?

Answer 13

• Studying how the magnetic field shift and changes over time
• Measuring Earth’s gravitational field
• Using Earthquakes

Question 14

What are the differences between P and S waves?

Answer 14

-P waves are pressure or compression waves

• They Travel by compressing the material in front of them
• They are faster

S waves are shear waves

• They Travel more slowly
• Cause much harder shaking

Question 15

How can we use the differences between a P and S wave to determine how far away an earthquake’s epicenter is?

Answer 15

P and S waves travel at different speeds, by measuring the arrival times, we can determine how far the earthquake’s epicenter is

Question 16

What is the theory of plate tectonics?

Answer 16

This is behavior of the plates at the boundaries between two plates moving over time

Question 17

Be able to describe the different types of boundaries found where plates meet.

Answer 17

Divergent Boundaries:

• Where two plates are separating causing the material to upwell from underlying mantle
• Sometimes called spreading centers
• Mostly found under oceans

Convergent Boundaries
-Where two plates are moving together and once plate slides under the other

-Transform Fault Boundaries
Plates may also be moving in opposite direction to each other

A link between spreading zones and help facilitate subduction of rocks

Question 18

What is a mid ocean ridge? How are they formed? What kind of boundary is this?

Answer 18

It is an elevated land under the ocean (like a mountain) which high levels of volcanic activity

The are formed when a new rock forms and as it cools it moves away from the spreading zone and contracts to form a newer ridge

Question 19

What are the differences between the three main types of volcanoes?

Answer 19

Strato

• Subduction of plates results in the melting of the mantle to produce magma
• Produces thicker magma so it flows short distances

Shield

• A hot spot develops under the crust and magma rises through the crust and erupts
• Magma is fluid and will flow larger distances

Cinder cone

• Short lived volcanoes (active for less than 1 year)
• Occur by themselves and build up from pyroclastic material which is ejected

Question 20

What is a caldera?

Answer 20

At the peak of many volcanoes there are craters which are 1km in diameter)

Question 21

Describe the process that created the Hawaiian islands chain.

Answer 21

Formed by a hot spot occurring in the middle of the pacific plate

Question 22

Provide some examples of locations in the solar system with volcanic activity.

Answer 22

The moon: Appears to be the same type of structure that creates low lying mare

Triton (Neptune’s moon)
Enceladus (Saturn’s moon)

Question 23

The Earth has stayed hot since it formed over 4.5 billion years ago. This is partially due to heat retention (it held onto its heat from formation), but also due to continued heating by what?

Answer 23

Radioactive decay of materials in the crust

Question 24

The Earth’s surface is relatively young. How old is it? and what is causing it to be resurfaced?

Answer 24

Few hundred million years old

Plate tectonics constantly shifting cause resurfacing

Question 25

Why did the Moon cool off more rapidly?

Answer 25

Because it is so small

Question 26

What is the dominant process that ‘sculpts’ the Moon’s surface presently?

Answer 26

Eons of asteroids and comments slamming into the moon’s surface has sculpted its shape

Question 27

How is the Moon’s regolith created?

Answer 27

Meteorite impacts

Question 28

Provide a basic description of the tidal force

Answer 28

Tidal forces occur when there is a difference in gravity between two sides of a celestial body caused by the attraction of another body

Question 29

How are the tides created on Earth?

Answer 29

The moons gravitational pull causes the water in earth’s ocean to rise

Question 30

What three effects ‘complicate’ the ocean tides?

Answer 30

• The Earth’s rotation drags tidal bulges out of line
• Coastlines cause high tides to occur in a pattern
• The sun contributes to tidal forces too

Question 31

What effect does the Sun have on the ocean tides?

Answer 31

The sun is massive but further away, however, its gravitation force is much stronger

But since the moon is closer it has a larger effect on tides

Question 32

What does it mean when we say the Moon is in a synchronous rotation with the Earth?

Answer 32

It is tidally locked

Question 33

Explain how the Moon is slowly moving away from us.

Answer 33

Due to tidal forces

The tides slow the earth’s spin which increases the moon’s spin causing it to slowly move further away

Question 34

How do we know the Moon is moving away from us?

Answer 34

Astronauts placed laser reflectors on the moon to measure motions

Question 35

Describe how seismic waves change when they move from one type of rock to another

Answer 35

They bend according to the rock they pass through

Question 36

What type of evidence do we have to prove that the Earth has differentiated?

Answer 36

Seismic studies show both the Earth and Moon increase in density at their cores

We can map the transition from dense core to mantle to the least dense parts

Question 37

Why is the mean density of the Moon much less than the Earth

Answer 37

The interior of the moon is similar to the material on Earth’s mantle, making it less dense

Question 38

What are the three basic factors that shape terrestrial surfaces?

Answer 38

Impacts with asteroids and comets

Erosion from liquid water and wind

Geological processes

Question 39

Expand on what ‘geologic processes’ are, give some examples.

Answer 39

It is any form of geological activity

E.g. mountain ranges, earthquakes, sinkholes, etc.

Question 40

How long does it take for the mantle to complete one full convection cycle

Answer 40

200 million years