Chapter 4: Earth’s Structure and Motion 4.1: Earth’s Formation 4.2: Earth’s Rotation 4.3: Earth’s Revolution

4.1: Earth’s Formation Origin of the Solar System 1. Nebular Hypothesis Cloud of gas and dust rotating slowly Rotation speed increased Material gathered to its center

4.1: Earth’s Formation Draw figure on pp 70-71 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.

4.1: Earth’s 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

4.1: Earth’s 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 KM=55 united states

4.1: Earth’s Formation Earth's Interior Space collisions have changed Earth to look the way it does presently

4.1: Earth’s 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

4.1: Earth’s 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.

4.1: Earth’s 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 sun’s warmth and winter’s cold cannot penetrate there.

4.1: Earth’s 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

4.1: Earth’s 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

4.2: Earth’s Rotation Evidence for Rotation What is significant about Foucault's pendulum and it 11o shifts each hour? It proves that the earth is rotating

4.2: Earth’s 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

4.2: Earth’s 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

4.2: Earth’s 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.

4.2: Earth’s Rotation Effects of Rotation Earth rotates counterclockwise = Sun appears to rise in east

4.2: Earth’s 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

4.2: Earth’s 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)

4.2: Earth’s 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

4.3: Earth’s 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.

4.3: Earth’s 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

4.3: Earth’s 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 ...

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

4.3: Earth’s 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 @ max tilt towards sun. North Pole = 24 hrs. of ... South Pole = 24 hrs. of ...

4.3: Earth’s Revolution Effects of Revolution and Tilt Winter Solstice - first day of winter, ~ December 21, shortest day, Northern Hemisphere @ max tilt away from sun. North Pole = 24 hrs. of darkness South Pole = 24 hrs. of daylight

4.3: Earth’s 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