Chapter 5 Earth and Its Moon

Chapter 5 Earth and Its Moon

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Units of Chapter 5 Earth and the Moon in Bulk The Tides Atmospheres Interiors Surface Activity on Earth The Surface of the Moon Magnetospheres History of the Earth–Moon System

Question 1 a) an atmosphere. b) a hydrosphere. c) a magnetosphere. d) It lacks all of the above. The Moon’s internal structure is similar to Earth’s, but the Moon lacks Answer: d

Question 1 a) an atmosphere. b) a hydrosphere. c) a magnetosphere. d) It lacks all of the above. The Moon’s internal structure is similar to Earth’s, but the Moon lacks Both the Earth and Moon have a core, mantle, and crust, but the Earth has a liquid water-rich layer, air, and a magnetic field.

Earth and the Moon in Bulk

The Tides Tides are due to gravitational force on Earth from Moon – force on near side of Earth is greater than force on far side. Water can flow freely in response.

The Tides The Sun has less effect, but it does modify the lunar tides.

Question 2 a) new moon b) waxing crescent moon c) full moon d) third quarter moon e) both new and full moon At what lunar phase would the variation between high & low tides be greatest? Answer: e

Question 2 a) new moon b) waxing crescent moon c) full moon d) third quarter moon e) both new and full moon At what lunar phase would the variation between high & low tides be greatest? At new and full moon phases, the Sun and Moon combine to stretch the Earth and its oceans even more. We see higher high tides and lower low tides.

The Tides Tides tend to exert a “drag” force on Earth, slowing its rotation. This will continue until Earth rotates synchronously with the Moon, so that the same side of Earth always points toward the Moon.

The Tides This has already happened with the Moon, whose near side is always toward Earth.

Question 3 a) the Sun’s gravity b) Earth’s magnetic field c) Earth’s tidal force d) the solar wind e) the Moon’s magnetic field What force riveted the Moon’s near side to constantly face Earth? Answer: c

Because of Earth’s tidal force, the Moon spins once a month. Question 3 a) the Sun’s gravity b) Earth’s magnetic field c) Earth’s tidal force d) the solar wind e) the Moon’s magnetic field What force rivets the Moon’s near side to constantly face Earth? Just as the Moon creates tides on Earth with its gravitational force, the Earth affects the Moon, too. Because of Earth’s tidal force, the Moon spins once a month.

Atmospheres The blue curve shows the temperature at each altitude. Troposphere is where convection takes place – responsible for weather.

Atmospheres Convection depends on warming of ground by the Sun.

Atmospheres Ionosphere is ionized by solar radiation, and is a good conductor. Reflects radio waves in the AM range, but transparent to FM and TV. Ozone layer is in the stratosphere and absorbs ultraviolet radiation.

Earth’s Growing Ozone Hole Chlorofluorocarbons (CFCs) have been damaging the ozone layer, resulting in ozone hole. 1 chlorine atom can destroy up to a 100,000 ozone molecules. It will be decades before the hole will go away.

Question 4 A planetary atmosphere with ozone could protect surface dwellers from a) ultraviolet radiation. b) charged particles in the solar wind. c) meteor impacts. d) optical radiation. e) radar waves. Answer: a

Question 4 A planetary atmosphere with ozone could protect surface dwellers from a) ultraviolet radiation. b) charged particles in the solar wind. c) meteor impacts. d) optical radiation. e) radar waves. Ozone in the stratosphere (about 30-50 km high) absorbs UV light, and heats the upper atmosphere.

Atmospheres Surface heating: Sunlight that is not reflected is absorbed by Earth’s surface, warming it. Surface re-radiates as infrared thermal radiation. Atmosphere absorbs some infrared, causing further heating.

Atmospheres This is known as the greenhouse effect.

Question 5 The principal greenhouse gases in our present atmosphere are a) hydrogen and helium. b) oxygen and nitrogen. c) water vapor and carbon dioxide. d) methane and ammonia. e) sulfuric acid vapor and CO2. Answer: c

Question 5 The principal greenhouse gases in our present atmosphere are a) hydrogen and helium. b) oxygen and nitrogen. c) water vapor and carbon dioxide. d) methane and ammonia. e) sulfuric acid vapor and CO2. A greenhouse gas lets shorter- wavelength light pass through, but absorbs longer-wavelength light.

The Greenhouse Effect and Global Warming There is extremely strong evidence that Earth is getting warmer. The cause of this warming is a subject of intense debate; many scientists believe it is related to the corresponding increase in atmospheric carbon dioxide.

Greenhouse Effect Some greenhouse gas is necessary. Without a trace of GHG Earth would be -19 C instead of +14 C. Too much GHG and Earth gets too hot. GHG such as water vapor, CO2 and Methane.

Question 6 Without the greenhouse effect in our atmosphere a) we would not have to worry about ecological problems. b) the Earth’s oceans would be frozen. c) the amount of nitrogen & oxygen would be much less. d) the icecaps would have melted. e) global warming would still occur. Without the greenhouse effect in our atmosphere Answer: b

Question 6 Without the greenhouse effect in our atmosphere a) we would not have to worry about ecological problems. b) the Earth’s oceans would be frozen. c) the amount of nitrogen & oxygen would be much less. d) the icecaps would have melted. e) global warming would still occur. Without the greenhouse effect in our atmosphere Earth’s greenhouse effect makes the planet about 40° C hotter than it would otherwise be. This raises the average surface temperature above the freezing point of water.

Interiors Seismic waves: Earthquakes produce both pressure and shear waves. Pressure waves will travel through both liquids and solids. Shear waves will not travel through liquids, as liquids do not resist shear forces. Wave speed depends on density of material.

Interiors The pressure wave is a longitudinal wave, whereas the shear wave is a transverse wave. A shear wave cannot propagate within a liquid.

P - wave

S - Wave

Interiors Can use pattern of reflections during earthquakes to deduce interior structure of Earth.

Interiors Currently accepted model

Interiors Mantle is much less dense than core. Mantle is rocky; core is metallic, consisting of iron and nickel. Outer core is liquid; inner core is solid, due to pressure. Volcanic lava comes from mantle, allows analysis of composition.

Surface Activity on Earth Continental drift: Earth’s entire surface is covered with crustal plates, which can move independently. At plate boundaries, earthquakes and volcanoes can occur. Volcano earthquake Plate line Drift Direction

San Andreas Fault 2 inches per year 21 feet in 1906 quake

Surface Activity on Earth Plates moving away from each other create rifts.

5.5 Surface Activity on Earth If we follow the continental drift backward, the continents merge into one, called Pangaea.

The Surface of the Moon The Moon has large dark flat areas, due to lava flow, called maria (early observers thought they were oceans).

The Surface of the Moon The far side of the Moon is relatively unmarked.

Question 7 Lunar maria are found a) uniformly all over the Moon. b) mostly on the side facing Earth. c) mostly on the far side of the Moon. d) only in the dark areas, out of sunlight. e) in the highlands, among mountains. Lunar maria are found Answer: b

Question 7 Lunar maria are found a) uniformly all over the Moon. b) mostly on the side facing Earth. c) mostly on the far side of the Moon. d) only in the dark areas, out of sunlight. e) in the highlands, among mountains. Lunar maria are found Because the Moon keeps its near side always facing Earth, that side has a thinner crust, and is also less cratered.

The Surface of the Moon Crater formation: Meteoroid strikes the Moon, ejecting material; explosion ejects more material, leaving a crater.

The Surface of the Moon Craters are typically about 10 times as wide as the meteoroid creating them, and twice as deep. Rock is pulverized to a much greater depth. Most lunar craters date to at least 3.9 billion years ago; much less bombardment since then.

The Surface of the Moon Very large and very small lunar craters

The Surface of the Moon Regolith: Thick layer of dust left by meteorite impacts The Moon is still being bombarded, especially by very small “micrometeoroids”; softens features.

Magnetospheres The magnetosphere is the region around Earth where charged particles from the solar wind are trapped.

Magnetospheres These charged particles are trapped in areas called the Van Allen belts, where they spiral around the magnetic field lines.

Question 8 a) ozone layer. b) exosphere. c) Van Allen radiation belts. d) corona. e) aurora borealis and australis. The region around Earth where the magnetic field traps charged particles is the Answer: c

Question 8 a) ozone layer. b) exosphere. c) Van Allen radiation belts. d) corona. e) aurora borealis and australis. The region around Earth where the magnetic field traps charged particles is the The Earth’s magnetosphere influences the charged particles of the solar wind. Some particles are channeled toward the poles, creating the aurora.

Magnetospheres Near the poles, the Van Allen belts intersect the atmosphere. The charged particles can escape; when they do, they create glowing light called an aurora.

Question 9 a) a compass pointing north b) aurorae c) the Van Allen radiation belts d) volcanic eruptions e) the comet-like tail of charged particles that extends past our Moon Which of these is NOT a result of the Earth’s magnetic field? Answer: d

Question 9 a) a compass pointing north b) aurorae c) the Van Allen radiation belts d) volcanic eruptions e) the comet-like tail of charged particles that extends past our Moon Which of these is NOT a result of the Earth’s magnetic field? Our planet’s magnetosphere is generated by the Earth’s rotation and its liquid metal core. In contrast, the Moon doesn’t have a magnetic field.

History of the Earth–Moon System Current theory of the Moon’s origin: glancing impact of Mars-sized body on the still-liquid Earth caused enough material, mostly from the mantle, to be ejected to form the Moon. Computer model

History of the Earth–Moon System Four billion years ago, the Moon had many craters but no maria. By three billion years ago, the maria had formed. Now, they also are covered with craters.

Question 10 a) The fission theory b) The giant impact theory c) The capture theory d) The co-formation theory e) The fusion theory Today, which of these theories best explains the Moon’s origin? Answer: b

Question 10 a) The fission theory b) The giant impact theory c) The capture theory d) The co-formation theory e) The fusion theory Today, which of these theories best explains the Moon’s origin? The giant impact theory seems to explain why the Moon is similar to Earth’s mantle, and why it doesn’t have a dense core.

Giant Impact Theory

Summary of Chapter 5 Earth’s structure, from inside out: Core, mantle, crust, hydrosphere, atmosphere, magnetosphere Tides are caused by gravitational effects of Moon and Sun. Atmosphere is mostly nitrogen and oxygen; thins rapidly with increasing altitude. Greenhouse effect keeps Earth warmer than it would otherwise be.

Summary of Chapter 5, cont. Can study interior by studying seismic waves. Crust is made of plates that move independently. Movement at plate boundaries can cause earthquakes, volcanic activity, mountain ranges, and rifts. New crust formed at rifts shows evidence of magnetic field reversals. Earth’s magnetic field traps charged particles from solar wind.

Summary of Chapter 5, cont. Main surface features on Moon: maria, highlands Heavily cratered No atmosphere and large day–night temperature excursions Tidal interactions responsible for synchronicity of Moon’s orbit

Summary of Chapter 5, cont. The Moon’s surface has both rocky and dusty material. There is evidence for volcanic activity. The Moon apparently formed as a result of a large object colliding with Earth.