Download Foundation 1 - Discovering Astronomy

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
Collision
of two plates
separation
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
Gravitation
al forces
produce the
tides and
keep the
same side
of the Moon
always
facing the
Earth
Synchronous 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-Check
1: 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.