Download The Earth Moon System

The Earth Moon System
Formation, Development, and
Current State
We were wrong…
• It was once believed that Earth was created,
instantly, 6000 years ago.
• Ancient thinkers like Aristotle and Leonardo da
Vinci saw fossils as evidence the Earth was much
older.
• Lord Kelvin used heat to determine an age of 24400 million years old
• Arthur Holmes was the first to get a near accurate
age of the Earth using, determining the earth to be
about 1.6byo using radioactive decay.
• Later, improved methods of radiometric dating led
to a much more accurate age of the Earth.
Formation
• About 4.5 billion years ago, Earth, along
with the other planets in our solar system
began to take shape.
• They formed in accretion disks.
• The material that formed the Earth was
created in supernovas.
Proto-Earth
• Within 10-20 million years Earth, slightly smaller
than today, had formed from the accretion disk
located about 150,000,000km from the sun.
• It is hypothesized that another, even smaller planet
was also forming at about the same distance.
• This planet, Theia, was about the size of Mars.
Giant Impact Hypothesis
• Shortly after the formation of these two planets,
Theia struck Earth with a glancing blow.
• This impact liquefied Earth and ejected a large
amount of molten material.
• The ejected material formed the Moon.
• The remainder of Theia sunk to the center of Earth
to help form its iron core.
• http://upload.wikimedia.org/wikipedia/commons/d
/d1/Big_Slash.gif
• There are some other, less likely idea’s as to how
the Moon formed
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Co-Formation Hypothesis
• Before, we visited the Moon and were able
to analyze its contents, it was thought that
the Moon formed at the same time and
location as Earth.
• This would have left the Moon rotating
directly above the equator with much more
Iron than it currently has.
Fission Hypothesis
• It was also once believed that centrifugal forces
pulled a chunk of earth out into space leaving a
basin behind which later formed the Pacific
Ocean.
• This would have required the Earth to be spinning
much faster than it does today.
• It also would have formed the Moon rotating
directly above the Equator.
• These facts make this an unlikely hypothesis.
Capture Hypothesis
• Because the Moon’s orbit is not directly above the
equator, it was once believed that the moon was
formed elsewhere in the Solar System and later
captured by Earth’s gravity.
• For this to have occurred the Earth would have
needed a much larger atmosphere to slow down
the approaching Moon.
• This too is very unlikely.
Explanation
• The Giant impact Hypothesis is the most
likely because it helps explain other features
about the Earth Moon system.
• Large amount of Iron in the core
• Still molten mantle
• Tilt of the Earth
• Speed of Rotation of Earth
A Changing Planet Time Line
• 4.5 bya - Magma Earth
• 4.4bya - Ocean Earth
– Carbon dioxide atmosphere, iron rich oceans
• 3.4bya - Continents form
– Granite floats on magma
• 2.2-1.5bya - Blue Planet
– Stromatolites release oxygen that turns oceans
and sky blue.
Time Line (cont)
• 1.0bya Rodinia
– Super-continent
– Trilobites best evidence
• 700mya Snowball Earth
– Caused by massive super-continent
• 630mya Cambrian Explosion
– Shallow seas allows for evolution of a wide variety of
life
– Evidence found in Burgess Shale
Time Line (cont)
• 300mya - Animals/Plants moved on land
– Oxygen in atmosphere created ozone that protected
animals and plants from UV rays
• 250mya - Massive volcanic eruptions
– Led to extinction of 95% of living things
– Creation of Pangea
• 235mya - Dinosaurs began to rule
– “Lukewarm” blooded, allowed them to survive in hot,
oxygen rich environment.
Time Line (cont)
• 180mya - Pangea breaks up.
– Dinosaurs survive
• 65mya - KT Boundary
– Asteroid/Comet impacts Mexico
– Volcanoes erupting in India
– Most dinosaurs go extinct
Time Line (cont)
• 50mya - Mammals began to flourish
– Uplift and Erosion shape surface of Earth
• 2mya - Human ancestors leave Africa
– Ice Ages send glaciers back and forth across the
continents
• 10,000ya - Last Ice Age retreats
– Human civilization begins
The Future
• +15000y - New Ice Age
– Within the next 15000 years a new Ice Age will
begin.
• +200my - New Super-Continent forms
• +2by - Mantle and Core cool
– Stops tectonic movement
– Stops magnetic field
Earth
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Earth is the 5th largest planet.
12,800km diameter.
Not a perfect sphere
Centrifugal force makes the circumference
around equator bigger than circumference
around poles. (difference of 67km)
• Oblique Spheroid
Earth’s Axis
• Earths axis is an imaginary line that runs
through the Geographic North and South
Poles.
• The Earth spins about this axis once every
23hours 56minutes.
• The axis is tilted at an angle of 23.5º from
vertical.
• This tilt is responsible for the seasons.
Seasons
• The seasons have differing weather patterns for
two reasons
• 1. The angle of the Sun’s rays varies from most
direct in the summer (hotter) to least direct in the
winter (cooler)
• 2. The length of day varies from longest in the
summer to shortest in the winter, giving the Sun’s
rays less time to warm the Earth.
• The Northern and Southern Hemispheres have
opposite seasons.
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Solstices
• The solstices occur on when the amount of
daylight is the greatest or least and the angle
of the Sun’s Rays are the most or least
direct.
• Winter Solstice - December 21st
• Summer Solstice - June 21st
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Equinoxes
• An equinox occurs when there is exactly
12hours of daylight and the Sun’s rays are
pointing directly at the equator.
• Spring Equinox - March 21st
• Fall Equinox - September 23rd
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Earth’s Structure
• Earth is comprised of several layers.
• These layers are separated due to their
density.
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Crust
Upper Mantle
Lower Mantle
Outer Core
Inner Core
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Crust
• The Crust is the layer of the Earth we all
walk on.
• 0-35km below the surface of the Earth.
• Two different types
– Granite Crust - Covers continents, thicker
– Basaltic Crust - Ocean Floor, thinner
• Crust contains rock in all phases of the rock
cycle.
Mantle
• The Mantle is the area of rock between the
core and the crust. (35-3000km)
• The rock is plastic in characteristic and
flows too slowly to be considered a liquid.
• The difference between the upper and lower
mantle is due to the way seismic vibrations
pass through.
• Seems to be pressure related.
Outer Core
• Liquid layer of Iron and Nickel located
between the inner core and the lower
mantle.
• 3000-5000km deep
• Predominantly responsible for Earth’s
magnetic field due to the rapid movement of
the liquid metal.
Inner Core
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The center of the Earth.
Solid alloy of nickel and iron.
5000-6400km deep
Thought to be hotter than the surface of the
sun. (Remains solid due to immense
pressure)
Earth’s Magnetic Field
• As a result of the rapidly spinning liquid
metal found in the outer core, Earth has a
magnetic field, similar to a giant bar
magnet.
• This magnetic field protects us from
harmful rays and particles emitted from the
sun.
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Magnetic Poles
• Just like a bar magnet, Earth has magnetic north
and south poles.
• A compass is a small magnet that aligns its self to
Earths magnetic field, always pointing to the
North and South Magnetic Poles.
• A compass above either magnetic pole will point
in random directions.
• These poles do not align with Geographic poles.
• They can move up to 15km a year.
The Moon
• The Moon is Earth’s only natural satellite.
• It is the fifth largest moon in the Solar System.
• The Moon’s orbit ranges from a distance
363,000km to 406,000km.
• The moon is about 3500km in diameter
• This gives the moon roughly 1/6th the gravity of
here on Earth.
Moon (cont)
• The moon takes 27.3 days to orbit the Earth.
• As the Earth is also moving during this time
the Moon completes its cycle of phases over
a period of 29.5 days.
Structure of the Moon
• Like Earth, the Moon has a crust, mantle
and core.
• Unlike Earth, only a small portion of the
Moon’s core is still liquid.
• The Moon has cooled significantly since it
was formed.
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Surface of the Moon
• The Moon’s surface has several important
features.
• Maria - dark, relatively featureless plains on the
moon.
– Formed as lava filled depressions left by impacts.
• Terre - Lighter colored highlands of the moon
– Mountains exist only around the edges of Maria and
were not formed by tectonic movement.
Surface of the Moon (cont)
• Regolith - the “soil” of the Moon
– Result of many impacts breaking up rock into
very fine particles.
– Maria has 3-5m of regolith, Terre has 10-20m.
• Impact Craters - form as asteroids, meteors,
and comets impact the Moon.
– Lack of atmosphere leaves these craters
undisturbed.
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Motion of the Moon
• If we could view the Earth moon system
from above the North Pole, the moon would
rotate around the Earth counterclockwise.
• It also rotates once about its axis, again in a
counterclockwise motion.
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Tides
• One of the most obvious effects of the relationship
between the Moon and Earth are tides.
• Tides are the result of the gravitational pull of the
Moon and the Sun on Earth’s oceans.
• They can cause the level of the ocean to change as
much as 17 meters depending on the location
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Types
• There are two types of tides.
• Spring tides occur when the Moon, Earth and Sun
form a straight line.
– These tides are the most extreme, highest and lowest.
– Gravity of Sun and Moon work together.
• Neap tides occur when the Moon, Earth, and Sun
form a right angle.
– These tides have the least variation between high and
low tide.
– Gravity of Sun and Moon are work against each other.
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Sides of the Moon
• Because the Moon rotates exactly once for each
revolution around the Earth, the same side of the
Moon always faces the Earth.
• We call this side the Near Side of the Moon.
• The Far Side of the moon is often incorrectly
called the Dark Side of the Moon.
• The Far Side of the moon has almost no Maria.
– Likely due to lack of tidal forces from Earth.
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Phases of the Moon
• Like any sphere lit by a single source, half of the
moon is always dark.
• As the Moon spins around Earth, we see varying
amounts of this lit portion.
• When the amount of the lit Moon we can see each
night is getting larger the moon is considered to be
waxing.
• The Moon is considered to be waning as the lit
portion decreases each night.
New Moon
• The new moon occurs as the moon is
between the earth and the sun.
• The new moon is not visible.
• It rises and sets with the sun.
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Waxing Crescent
• Is the phase in between the New Moon and
the First Quarter
• The edge of the Moon is on the right.
• They rise between sunrise and noon and set
between sunset and midnight.
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First Quarter
• The First Quarter occurs when the Moon
and the Sun form a right angle with Earth.
• The curved side of the Moon is on the right.
• Rises at noon and sets at midnight.
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Waxing Gibbous
• Occurs between the First Quarter and the
Full Moon.
• The more rounded side is on the right.
• Waxing Gibbous moons rise between noon
and sunset, and set between midnight and
dawn.
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Full Moon
• Full Moons occur when the Earth is
between the Moon and the Sun.
• Full Moons rise at sunset and set at sunrise.
• A Blue Moon occurs when there are two
Full Moons in one month.
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Waning Gibbous
• The phase between a Full Moon and the
Last Quarter. Gets a little smaller each
night.
• The more rounded side is now on the left.
• Rises between sunset and midnight and sets
between sunrise and noon.
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Last Quarter
• Last Quarter occur when Moon Earth and
Sun form right angle.
• The round side of the Moon is on the left.
• Rises at midnight and sets at noon.
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Waning Crescent
• Phase between the Last Quarter and the
New Moon.
• Edge of moon on the left
• Rises between midnight and sunrise, sets
between noon and sunset.
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Eclipses
• An eclipse occurs as the shadow of the
Earth or Moon blocks the sun from the
other.
• Because the Moon revolves around Earth at
a slight angle, and is quite a distance from
Earth, rarely does the shadow of one
obscure the other.
Solar Eclipse
• Solar Eclipses occur as the Moon casts a shadow
on the Earth.
• The Moons shadow has two parts
– Umbra - darker, center part of the shadow
– Penumbra - lighter outer part of the shadow
• An area that lies in the Umbra will see a full solar
eclipse
• An area that lies in the penumbra will see a partial
solar eclipse.
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Occurrence
• Must occur during the New Moon phase.
• They occur somewhere on Earth about
every 18 months.
• A total solar eclipse occurs in any given
area of Earth about once every 370 years.
• As the shadow moves at 1700km/hr totality
only lasts for at most 7.5 minutes.
Lunar Eclipse
• A lunar eclipse occurs as the Moon passes through
the Earth’s shadow.
• Like solar eclipses, lunar eclipses vary according
to the part of the shadow that Moon passes
through.
• As the shadow occurs on the Moon it can be seen
from the entire hemisphere that can view the
Moon.
• Because of this Lunar Eclipses are seen more
frequently
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