Chapter 5

Earth and Moon

What do you think?

• Will the ozone layer, which is now being depleted, naturally replenish itself?

• Does the Moon have a dark side, where it is forever night?

• Does the Moon rotate, and if so, how fast?

• What causes the ocean tides?

• When does the spring tide occur?

Why might this planet be called the blue planet?

The Earth’s atmosphere has evolved over billions of years

• Earth’s early atmosphere was primarily hydrogen and helium left over from the formation of the solar system

• Earth’s second atmosphere was primarily CO2 and released from Earth’s interior by volcanoes

• Earth’s current atmosphere is a 4-to-1 mixture of nitrogen and oxygen which was created by biological activity.

Earth’s atmospheric layers are defined by temperature ranges

Earth’s protecting ozone layer

Earth’s Ozone Layer• Ozone is O3

• Protects the surface from hazardous UV radiation from the Sun

• Can be destroyed by synthetic chlorofluorocarbons (CFCs)

• Slowly replenishes itself as it is created from sunlight and lightning

• Earth’s protective ozone layer had to form before early life could move from the oceans onto dry land

Plate tectonics produced major changes to the Earth’s surface over the past 200 million years

Pangea

SEA FLOOR SPREADING

The sea floor between the North America and Europe is spreading apart

Earth’s surface is composed of about nine major plates which slowly move relative to one another

separation

Collision of two plates forms mountains

Plate tectonics is driven by convective currents in Earth’s mantle

Earth’s interior consists of a rocky mantle and an iron rich core

The Earth’s magnetic field is caused by dynamo movements in Earth’s core

The Earth’s magnetic field shield us from the stream of charged particles from the Sun called the solar wind

Relevance of Earth’s protective magnetosphere

• Solar Flares - violent explosions on the Sun releasing charged particles into the solar system

• Solar wind - dangerous stream of charged particles coming from the Sun

• Van Allen radiation belts - hazardous reservoir of charged particles surrounding Earth

• Northern Lights (Aurora Borealis)

Aurora as seen from space

Aurora surrounding

the north geomagnetic pole as seen from space

The Moon’s surface is

covered with craters,

plains, and mountains

Mare Imbrium

Visits to the Moon yielded invaluable information about its history

Lunar Soil is called

Regolith

Mare Basalt

Mare basalt is solidified lava similar to what composes rocks on Earth’s sea floor.

Anorthsite

Anorthsite is material from the original lunar crust sometimes called the genesis rock and is more than 4 billion years old

Impact Breccias

Impact Breccias are rocks formed from combining debris during a violent impact event

Likely interior of the Moon

The Moon probably

formed from debris cast into space when a

huge planetesimal

struck the young Earth

Gravitational forces

produce the tides and keep the

same side of the Moon

always facing the

EarthSynchronous rotation

The gravitational force between Earth and Moon results in tides

Large spring tides occur when the Sun and Moon are aligned such that they BOTH pull on the Earth’s water.

Smaller neap tides occur when the Sun and Moon are misaligned such that they pull on the Earth’s water in different directions.

Bouncing laser beams off the

Moon demonstrates that it slowly moving away from the Earth

What did you think?• Will the ozone layer, which is now being depleted, naturally replenish itself?

Yes, the ozone is created from normal oxygen molecules by the Sun’s ultraviolet radiation.

• Does the Moon have a dark side, where it is forever night?Half of the Moon is always dark, but that half is continually changing as the Moon orbits the

Earth.

• Does the Moon rotate, and if so, how fast?The Moon rotates at the same rate that it revolves around the Earth. If the Moon didn’t rotate,

then as it revolved we would see different sides of it, which we don’t.

• What causes the ocean tides?The tides are caused by gravitational forces, primarily from the Moon and Sun.

• When does the spring tide occur?Spring tides occur during each full and new Moon.

Self-Check1: Describe the chemical evolution of the Earth’s atmosphere.

2: Describe the basic characteristics of plate tectonics on the Earth, including the observational evidence and the underlying cause.

3: List the major divisions of the Earth’s interior and describe the chemical composition and relative physical conditions in each.

4: Describe the relationship of the Van Allen belts and the northern lights to the Earth’s magnetic field.

5: List the various layers in the Earth’s atmosphere and describe the physical characteristics by which they differ.

6: List and describe the nature and probable origin of lunar surface features visible in photographs.

7: Indicate the range in ages of lunar rocks taken from different areas on the lunar surface and explain what they indicate about the stages in the formation of the moon.

8: Describe the key elements of the collisional ejection theory and summarize the evidence that might support it.