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Earth
Our Home Planet
Where did it come from?
• Gas and dust in the universe accreted and
differentiated to form our solar system and
Earth
Differentiated?
• Yes, this means that the heavier element
fell to the center while the lighter ones
were pushed to the top
LUNA
Earth’s Single moon
• Composed of
Basalt rock
• Evidence on lava
flows (Maria)
• Tidally locked
with earth.
How the tides work
• Tides – Caused by the
gravitational pull of the sun
and the moon.
• Water is pulled toward the
moon causing a high tide.
• Additionally, the solid portion
of the earth is also pulled
toward the moon leaving a
bulge on the opposite side of
the earth.
• High tides occur on both sides
of the planet hence you have
high tide twice a day
approximately every 12 hours.
• http://videos.howstuffworks.co
Alta High Astronomy
m/hsw/10000-the-moon-tidesvideo.htm
Spring and Neap Tides
• When the sun and
moon are aligned on
the same side you get
a higher than normal
tide called a spring
tide.
• When the are on
opposite sides you
get a lower than
normal tide called a
Neap tide.
Alta High Astronomy
Seismic Activity
Seismic Activity of our Planet
• We have learned
much about the interior
of the earth from
seismic waves.
These waves, caused
by earthquakes and
the shifting of the
tectonic plates come in
two varieties:
– Primary or Pressure
waves (P-waves) – are
the first to radiate from
an earthquake, they
are longitudinal in
nature,
– Secondary or Shear
Waves (S-Waves)
arrive later, these are
transverse in nature
Plate Tectonics
• The ASTHENOSPHERE is the region of
the earth that the plates slide over.
• Plate boundaries sometimes collide or
sub-duct resulting in seismic activity
• We call these plate boundaries fault lines
and we live right on top of one!!
Habitability of Earth
• The biosphere is the portion of earth in which all known
life forms exist. It occupies a thin layer of air
(atmosphere), water (hydrosphere), and land
(lithosphere).
Our atmospheric Gases
• N
• O2
• Trace gases
like Argon
Atmospheric Structure
• Atmosphere –
– Troposphere – Below 12 Km –
– Stratosphere - Above 12 to
about 50 Km
– Mesophere – 50 – 80 Km
– Ionosphere – Above 80 km
– Magnetosphere – High above
our atmosphere.
– Troposphere – is where
convection occurs due to
surface heating, this gives us
wind.
– Ozone layer is between the
stratosphere and the
mesosphere – this protects us
from much ultraviolet radiation.
What Causes the Wind?
• Wind is caused by Convection, which is defined as the
mass movement of particles.
• Solar heating of the air causes it to become less dense,
hence warm air rises, and the denser, colder air falls to
take its place. This causes what we call wind.
Is Earth A Magnet?
What Causes a Magnetic Field?
• It is theorized that the earth’s
magnetic field is caused by its
“rapidly” spinning, molten, iron
core.
• This “dynamo” effect creates
the magnetic field which
surrounds the earth.
• This is known as the dynamo
theory of magnetism and is
replicated by electrical
generators which use a rapidly
spinning loop of wire to
generate electricity.
• Magnetic fields always
accompany electric fields.
Earth’s Other Atmospheric
Protection: The Magnetosphere
• The Magnetosphere is a magnetic field which surrounds
the earth. It consists of two doughnut shaped fields
called the Van Allen Belts.
• It protects the earth from harmful electromagnetic
radiation and the buildup of electric charge which could
discharge to the earth
Side Effects