Chapter 4: Earths Structure and Motion

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Chapter 4 Earths Structure and Motion

• 4.1 Earths Formation
• 4.2 Earths Rotation
• 4.3 Earths Revolution

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4.1 Earths Formation

• Origin of the Solar System
• 1. Nebular Hypothesis
• Cloud of gas and dust rotating slowly
• Rotation speed increased
• Material gathered to its center

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4.1 Earths Formation

• d. Interior (core) became very hot hydrogen
  fusion Sun born
• e. Excess material went into space
  planetesimals beginning of Solar System
• Draw figure on pp 70-71
• Origin of the solar system.

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4.1 Earths Formation

• Earth's Size and Shape
• Planetesimals collected more objects developing
  into planets/moons
• What is a sphere called that bulges at the
  center?
• How do we know that Earth is spherical shaped
  bulging at the center?

Oblate Spheroid
By measuring the weight of an object at several
locations on earth
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4.1 Earths Formation

• 4. 149 million sq. km. (29) is dry land
• 5. 361 million sq. km. (71) is covered by water
• 6. The total surface of Earth is ...

510 million KM55 united states
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4.1 Earths Formation

• Earth's Interior
• Space collisions have changed Earth to look the
  way it does presently

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4.1 Earths Formation

• 2. Layers of the Earth
• Inner Core - Solid Iron and Nickel
• Outer Core - Liquid Iron and Nickel
• Mantle (thickest layer) Iron, Silicon, Magnesium
• Asthenosphere - Slush like layer
• Lithosphere - More rigid than the asthenosphere

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4.1 Earths Formation

• 3. Crust (earth's surface, thinnest layer) Rock
• Earth's Heat
• How did originally generate heat?
• Why is earth loosing heat presently?

Meteorite impact, compression and Radioactive
decay
Rocks lose heat to the atmosphere, crustal
thickness varies, and radioactivity decreases
with time.
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4.1 Earths Formation

• 3. Why does the temperature in caves remain
  constant?
• 4. After about 70 meters temperatures will begin
  to increase about 1o C every 40 m of depth

Because the suns warmth and winters cold cannot
penetrate there.
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4.1 Earths Formation

• Earth's Magnetic Field
• The North Pole attracts a compass needle - the
  positive end of a bar magnet
• The South Pole repels a compass needle - the
  negative end of a bar magnet

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4.1 Earths Formation

• C. The hypothesis explaining Earth's magnetic
  north/south is the liquid iron moving across
  Earth's weak magnetic field a stronger magnetic
  field is produced

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4.2 Earths Rotation

• Evidence for Rotation
• What is significant about Foucault's pendulum and
  it 11o shifts each hour?

It proves that the earth is rotating
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4.2 Earths Rotation

• 2. Evidence of Earth's rotation is seen in the
  Coriolis Effect - Northern Hemisphere winds are
  deflected to the right relative to Earth's
  surface which way are winds deflected in the
  Southern Hemisphere?

To the Left
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4.2 Earths Rotation

• Axis and Rate of Rotation
• Orbital Plane - an imaginary flat surface that
  Earth orbits the sun in.
• Earth's axis lies at a 23.5o tilt to its orbital
  plane

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4.2 Earths Rotation

• 3. Why does the Earth rotate at different speeds
  at different latitudes?

Because points at the equator have farther to
travel than points at the poles in the same
amount of time.
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4.2 Earths Rotation

• Effects of Rotation
• Earth rotates counterclockwise Sun appears to
  rise in east

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4.2 Earths Rotation

• 2. Measuring time
• Sidereal Day 23 hours 56 minutes Earth rotates
  360o
• Solar Day 24 hours (sunrise to sunrise 'true
  day') Earth rotates 361o
• Solar Noon - the sun is at its highest point
• Moves westward 1o every 4 minutes or 15o every
  hour Time Zones

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4.2 Earths Rotation

• Effects of Rotation Standard Time Zones
• Divisible by 15o or one hour time meridian
• Prime Meridian is in Greenwich
• West of Greenwich time moves back (earlier)
• East of Greenwich time moves forward (later)

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4.2 Earths Rotation

• 4. International Date Line
• Change the date (not the time)
• In the Pacific Ocean
• Moving west one day later
• Moving East one day earlier

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4.3 Earths Revolution

• Evidence for Revolution
• Revolution Orbit
• Different constellations are visible at different
  seasons (pp 714-717)
• What is parallax and how can you demonstrate it
  with a pencil?

Apparent shift in position of distant objects.
Hold a pencil up and look at it with one eye
open. Then close that eye and look at it with
your other eye open.
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4.3 Earths Revolution

• Path and Rate of Revolution
• Earth's revolution is the same as it rotation,
  what direction is this?
• The average distance the Earth is from the sun is
  150,000,000 km (1 au)
• Perihelion - when Earth is nearest the sun
  147.6 million km January 2
• Aphelion - when Earth is farthest away from the
  sun 152.4 million km July 4

Counterclockwise
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4.3 Earths Revolution

• 3. Zenith - the point directly above the
  observer
• 4. Altitude - Angular distance between the
  horizon and sun's position.
• Sun is at its zenith an altitude of ...
• Sun at its horizon an altitude of ...

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4.3 Earths Revolution

• C. Effects of Revolution Tilt
• In addition to Earth's revolution its tilt plays
  a large role in temperature, seasons, and days
• Hemisphere tilted towards the sun direct
  sunlight warmer temperatures and longer days.

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4.3 Earths Revolution

• B. Hemisphere tilted away from the sun
  indirect sunlight cooler temperatures and
  shorter days.
• C. Summer Solstice - first day of summer, June
  21, longest day, Northern hemisphere _at_ max tilt
  towards sun. North Pole 24 hrs. of ... South
  Pole 24 hrs. of ...

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4.3 Earths Revolution

• Effects of Revolution and Tilt
• Winter Solstice - first day of winter, December
  21, shortest day, Northern Hemisphere _at_ max tilt
  away from sun.
• North Pole 24 hrs. of darkness
• South Pole 24 hrs. of daylight

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4.3 Earths Revolution

• F. Vernal Equinox March 21 / Autmnal Equinox
  September 22
• Both day and night are equal length
• Neither hemisphere tilts towards the sun
• Sun overhead the equator at noon