The Planet Earth: Global
characteristics
•Kepler’s Laws
•P 2 = a3
• Size
•Newton’s Laws
– First measurement
•
•
•
•
•
Laws describing the planetary motion
• Speed, velocity, acceleration, force, inertia, mass,
balanced and unbalanced forces
Composition
Orbit around the Sun
Surface temperature
Mass
Density
• F= ma
•Law of Universal Gravitation
F =G
Weight and acceleration due to gravity
1. Weight – gravitational force attracting an object to the Earth.
2. How much is the weigh depends on how strong is the gravitational field of
the planet
W = Fgrav = G
m MEarth
2
REarth
MEarth
=a
2
REarth
a = 9.81 m / s 2 = g
W =mg
Calculating the mass of Earth
G
MEarth
= g = 9.81 m / s 2
2
REarth
REarth = 6378 km
Fgrav = m a
G
Mm
d2
G = 6.67 ×10 −11 N ⋅ m 2 /kg 2
2
Acceleration due to gravity
Measured for objects in free fall
R
g
MEarth = Earth
=
G
=
(6378 × 1000) 2 9.81
= 5.9 ×10 24 kg
−11
6.67 ×10
Fundamental
Astronomical constant
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Earth’s Interior
Kepler’s Laws reconsidered
Newton’s version of the Kepler’s 3rd empirical law:
4π 2 a 3
P =
G (m + M )
2
M
m
a
P
Units: P - in seconds, a - in meters.
Allows to calculate masses
Earth’s Interior
• Crust
– Mass, Density
– Under the ocean (basaltic rocks)
– Continental (silicates)
• Mantle
– Depth, conditions (lithosphere & partly melted zone),
samples
• Outer core
– Diameter, composition, density
• Inner core
– Diameter, composition, density
• Differentiation
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Earth’s Interior
• How can we study the interior of the
Earth?
– Magnetic Field of Earth
• Why does Earth have magnetic field
• Discovery of Earth’s magnetic field
• Characteristics
– Seismic waves
• Waves’ parameters
The Earth’s
magnetic field
Earth’s Lithosphere
80 km
(Melted)
3
Continental
Drift
• Geology
– Continents and oceans
not stable
– Plate tectonics
• “plate” +”tectonics”
• Definition
– ~ 12 major plates
– Convection
– Continental drift
The Crustal Plates of the Earth
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Basic kinds of interactions between
plates
The mid-ocean ridge
• Plates can pull apart
– Rate of separation
– Filling the space between receding plates
– Rift zones
•
•
•
•
Location
Length of active rifts, new Earth’s surface created
Age of ocean floor
Examples
http://pubs.usgs.gov/publications/text/baseball.html
Basic kinds of interactions between
plates
The Mariana Trench
• Plates can burrow under one another
– Subduction zone, subducted plate
– Thermal vents – earthquakes, volcanoes
– Ocean trench
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Basic kinds of interactions between
plates
• Plates can burrow under one another or
collide
– Mountains
– Alps, Himalayas (young)
Basic kinds of
interactions
between plates
• Plates can slide
alongside
– Cracks and faults
– San Andreas Fault
San Andreas
Fault
Cracks or Fault
Rift zone
(Photograph by Robert E.
Wallace, USGS.)
Trench
Mountain
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The Earth
Atmosphere
•Basic Facts
•Pressure exerted at see level
•Total mass
•Structure of the
atmosphere
2 sq km per yr
100 million yrs
•Atmospheric composition
at the Earth’s Surface
•72% N 21% O 1% Ar
•Water, CO2
•Dust, water droplets
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