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ES Lesson 11
Chapter 4: Earth’s Structure and Motion
I. Earth’s Formation
- Geology is the study of Planet Earth, its structure and
composition and how it has changed over time.
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.
2. 90% was collected at the center due to high pressure
A fussion began ---- Sun
3. 10% in the outer disk became planets.
B. Earth’s Size and Shape
1. The spinning motions of the young Earth caused it to
buldge 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 pole 194 equator)
3. This gives 1/3 evidence that the poles are closer to the
center of the earth.
4. 29% of earths surface is land
5. 71% covered with water
C. Earth’s Interior
1. Early earth surface was cratered by 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.
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
ES Lesson 11
D. Earth’s Heat
1. Events that lead to Earths layers due to heat creation on
earth
a. Meteorite impact
b. Weight of overlaying material
c. Decay of radioactive isotopes
E. Earth’s magnetic field
1. Believed to be created by the fluid of the outer core
moving around inner core.
2. Geographic N. Pole and Magnetic North Pole are in
different places ≈ 11° difference.