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Astronomy Today, Chapter 7
Earth: Our Home in Space
7.1 Earth in Bulk
1. Compare Earth's density with that of common substances.
a. Earth = 5500 kg/m3
b. Water = 1000 kg/m3
c. Air = 1.29 kg/m3
7.2 Earth's Atmosphere
Intro
2. Describe the chemical composition of Earth's atmosphere.
a. N2 = 78%
b. O2 = 21%
c. Ar = 0.9%
d. CO2 = 0.03%
e. H2O = 0.1-3%
Atmospheric Structure
3. Order and characterize the layers of our atmosphere.
a. Surface
b. Troposphere; warmest, densest; weather
c. Stratosphere; top has ozone
d. Mesosphere; bottom has ozone, very thin
e. Ionosphere; ionized by high energy solar radiation; very, very thin
4. Describe the protective function of the ozone layer.
a. Absorbs UV
Surface Heating
5. Describe the origin of the greenhouse effect.
a. Sun's visible light gets through and heats the surface
b. Ground releases the heat as infrared
c. CO2, water, and methane in the atmosphere absorb the heat
Origin of Earth's Atmosphere
6. Contrast the origins of Earth's primary and secondary atmospheres.
a. Primary: original atmosphere from accretion
b. Secondary: from within Earth, released by volcanic activity
7. Where did our oxygen come from?
a. Photosynthesis
7.3 Earth's Interior
Seismic Waves
8. Differentiate P- and S-waves.
a. P-waves are pressure waves; vibrate in the direction of motion
b. S-waves are shear waves; vibrate perpendicular
9. What do seismic waves tell us about the layers of the Earth?
a. P- and S-waves do through mantle  solid
b. Only P-waves go through outer and inner core  liquid
Modeling Earth's Interior
10. Order the layers of the Earth.
a. Crust, mantle, core
11. How have we obtained samples of the mantle?
a. Lava wells up from below the crust
b. = basalt
12. What is Earth's core temperature?
a. 5000 K
Differentiation
13. Contrast the compositions of the layers of the Earth.
a. Crust: light silicates like quartz
b. Mantle: heavier metal oxides and metal silicates like basalt
c. Core: dense iron and nickel metal
14. How was the Earth able to separate into distinct layers?
a. = differentiation; heavier material sinks, lighter stuff floats
b. How melted?
i. Collisions during formation
ii. Grinding into a ball
iii. Trapped radioactive isotopes
7.4 Earth's Magnetosphere
15. What is the origin of Earth's magnetic field?
a. Spinning, electrically conducting, liquid metal core
b. Not stable like a bar magnet
16. Describe the magnetosphere size, structure
a. Magnetic field lines exit and enter the poles forming a donut around Earth
b. Blown by the solar wind; boundary = magnetopause
c. Forms a long tail away from the Sun
d. Toward the Sun it extends 100,000 - 200,000 km
17. How are auroras generated?
a. Electrons and protons from the solar wind are trapped in the magnetosphere
b. They spiral along magnetic field lines down to the north pole
c. Collide with molecules in the atmosphere
7.5 Surface Activity
Effects of Plate Motion
18. Describe the effects at edges of moving tectonic plates.
a. Spreading with new crust forming
b. Earthquakes along faults
c. Subduction with volcanoes forming
d. Subsidence and uplift
What Drives the Plates?
19. What powers the motions of the tectonic plates?
a. Convection cells within Earth
b. Hot material rises, moves along the upper mantle, cools and sinks
c. Carries plates of crust with it
7.6 The Tides
Intro
20. How many daily tides are there in most places?
a. Two high and two low
Gravitational Deformation
21. What makes the tides?
a. Moon pulls bulge of water toward it
b. Opposite side has less pull, another bulge
c. Earth spins under the bulges
Effect of Tides on Earth's Rotation
22. How do the tides affect Earth's rotation and the Moon's revolution?
a. Earth drags the bulge ahead of the Earth-Moon line
b. Moon pulls on bulge slowing Earth's rotation
c. Bulge pulls on Moon speeding it up, moving it outward