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Chapter 4. Earth's Structure & Function
Transcript of Chapter 4. Earth's Structure & Function
4.1 Earth's Formation
A.Origin of the Solar System
1. Nebular hypothesis – the solar system formed about 4.6 billion years ago in a rotating cloud of dust and gas
4. 90% of the material was collected at the center due to high pressure A fusion began --- forming the Sun
5. 10% of the material in the outer disk became planets.
Earth's Size & Shape
1.The spinning motions of the young Earth caused it to bulge at the equator and flatten at the poles. (oblate spheroid)
2. One way scientists show the earth is not a perfect sphere is by measuring the weight of an object at several places (195 Newtons at pole 194 Newtons equator)
the farther away an object is from Earth's center the lighter it is
3. This gives evidence that the poles are closer to the center of the earth.
4. 29% of earths surface is land
5. 71% covered with water
1. Early earth surface was cratered like the moon.
2. Lots of rock and debris hitting the earth continuously.
3. The collisions were converted to heat. Causing most materials to melt.
4. While in a liquid form, materials separated according to density.
5. Earth's Layers
a. inner core – solid iron and nickel
b. outer core – liquid iron and nickel
c. mantle – solid but behaved like liquid due to pressure, made of iron, silicon and magnesium compounds
d. crust – thin rigid outer layer made of lighter rocks
1. Events lead to Earth's layers due to heat creation on earth include...
a. Meteorite impact
b. Weight of overlaying material causing compression in Earth's interior
c. Decay of radioactive isotopes -
*elements release heat as they became their more stable form.
2. Earth is losing it's heat slowly,
a. some rocks lose heat more slowly than others
b. the thickness of the crust varies from place to place
c. the percentage of radioactive materials in rocks varies
Earth's Magnetic Field
1. the magnetic field is believed to be created by the fluid of the outer core moving around inner core.
What makes a compass needle always point north?
It is aligning itself along the lines of force that make up the magnetic field.
2. Geographic N. Pole and Magnetic North Pole are in different places~ 11° difference.
OLD BOOK~ pg 124. Latitude & longitude lab
How is it that iron can account for 35% of earth's weight but only 5% of weight of the Earth's crust?
Scientists have only been able to drill 2km into the Earths Crust, but Japan is building a ship that scientists hope will drill through 6km of the ocean crust
How do you think our solar system was formed?
2. Nebulae - interstellar clouds of dust and gases (mostly hydrogen)
3. Dense parts of these clouds undergo
-when an object in space collapses under its own weight forming a rotating gas globule
Rotation - earth turns once on its axis every 24 hours
1. Foucault Pendulum ~Physicist Jean Foucault 1851 ~attached an iron sphere to a very long wire, making a pendulum 20 stories high. knowing that once a pendulum is set in motion, its direction of swing will not change.
2. However, he noted that every hour the path shifted 10 degrees, clockwise ~ concluded that the shift he saw was due to Earth rotation.
Other Evidence ~
2. Winds appear to be deflected due to rotation known as Coriolis Effect.
4. If Earth did not rotate, winds would blow in straight paths from areas of high pressure to low pressure.
Axis and Rate of Rotation
1.Axis of rotation – imaginary line that runs from the N. Pole to S. Pole that earth rotates around.
3. 24 hours for one rotation
4. Equator rotates faster than higher latitudes
Effects of Rotation
1.Gives day and night
2.From the North Pole it rotates counterclockwise causing the sun to rise in east and set in the west.
3.One rotation (360°) in 24 hrs or 15°/hr or 0.25°/minute.
4. Standard time zones are separated by 15° of longitude.
5. Time meridian occurs every 15° of longitude.
6. Prime Meridian is the 0° longitude which passes through Greenwich, England.
7.Travel west from 0° you would lose one hour every 15°, travel east you would gain 1 hour for every 15°.
III. Earth’s Revolution
A.Evidence of Revolution – movement of Earth around the Sun
1.The shifting position of earth in its orbit around the sun causes changes in the position of constellation.
2.Parallax – while the earth is moving in its orbit nearby stars seem to shift position when compared to more distant stars.
-if earth did not orbit neither one would occur (constellation or parallax)
B.Path and rate of revolution
1.Earth revolves in a counterclockwise motion when looked at from above the N. Pole
SIDENOTE: Clocks traditionally follow this sense of rotation because of the clock's predecessor: the sundial.
Clocks with hands were first built in the Northern Hemisphere, and they were made to work like sundials. In order for a horizontal sundial to work (in the Northern Hemisphere), it must be placed looking southward. Then, when the Sun moves in the sky (east to south to west), the shadow cast on the opposite side of the sundial moves with the same sense of rotation (west to north to east)
2. Earth’s orbit is an ellipse – causing the distance between the earth and sun to change constantly
3. At Perihelion(nearest the sun) - 147.6 million km, occurs on January 2
4. At Aphelion(farthest the sun) – 152.4 million km, occurs on July 4
5.One trip around takes 365.25 days or 1 year.
6.Revolves at a rate of about 1°/day
a. Overhead (90°) Zenith
b. Horizon (0°)
c. Altitude – angular distance between the Sun and Horizon – In the US the Sun is always below Zenith (except Hawaii)
C. Effects of Revolution and Tilt
1.Causes our seasons
2.Varies the time of day and night
3.Causes one hemisphere to be tilted toward the sun giving it more direct daylight causing warmer temperatures
4.1st day summer – biggest tilt toward sun occurs June 21st – summer solstice (longest day of year)
a. Sun is directly over 23.5° N latitude or the tropic of cancer
b. Every point north of 66.5° N Artic circle experiences 24 hours of daylight
5.1st day of winter – biggest tilt away from the sun occurs December 21 shortest day of the year.
a. Sun directly over Tropic of Capricorn 23.5°S latitude
b. Every point north of 66.5°N experiences 24 hrs of darkness
6. 2 days experiences no tilt
a. vernal equinox (spring) March 21
b. autumnal equinox (fall) September 22
1. what evidence is there for Earth's revolution around the sun?
2. Describe the shape of Earth's orbit and explain how Earth's position relative to the sun changes as Earth revolves.
3. Name the solstices & the equinoxes when do they happen?
8.International dateline imaginary line that represents the longitude at which the date changes.
traveling westward across you add a day to your watch
traveling eastward across you subtract a day
2. It is tilted 23.45 degrees from perpendicular
A. Evidence for Rotation
NatGeo -What if the Earth Stopped Spinning
Prep for ES0402
Prep for ES0402