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saturnbutton1.JPG (21728 bytes)Earth - Atmosphere Questions

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Q1.  What are the primary chemical constituents of Earth’s atmosphere? What is unusual about its composition, compared to other planets? Why is this unusual material present? Answer

Q2.  Describe the thermal structure (changes in temperature with altitude) of Earth’s atmosphere. What unusual feature does our atmosphere have in this regard, compared to other planetary atmospheres? Answer

Q3.  What are the astronomical causes of climate changes, such as the periodic occurrence of ice ages? Answer

Q4.  Earth’s atmosphere is composed mostly of nitrogen and oxygen. Why is there so little carbon dioxide in our atmosphere, compared to other planets? Why is there so much oxygen? Answer

Q5.  What happened to Earth’s original primary atmosphere? Where did the present secondary atmosphere come from? What happened to all the carbon dioxide that should be in our atmosphere? Answer

Q6.  What three factors may cause Earth’s climate to go into an ice age? Answer

Q7.  How did the earth's atmosphere become rich in molecular oxygen (O2)? Answer

Q8.  Describe the changes in the temperature in Earth’s atmosphere with increasing altitude. Answer

Q9.  Earth’s atmosphere is described as consisting of 4 layers. What are these 4 layers? Describe a distinguishing characteristic for each layer. Answer

Q10.  How does the thermal structure of Earth’s atmosphere compare to that of Venus’ atmosphere? Answer

Q11.  What event do astronomers believe caused the extinction of the dinosaurs? What evidence supports this idea? Answer

Q12.  What controls the temperature of Earth’s atmosphere? Describe both the physical principle and the sources of energy. Answer

Q13.  What are the major constituents of Earth’s atmosphere? In what way are they unusual for an atmosphere? Answer





saturnbutton1.JPG (21728 bytes)Green House Effect Questions

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Q1.  Explain in some detail why the inside of a car gets warm, compared to the air outside, when parked in the sunshine? Answer

Q2.  What role does carbon dioxide play in affecting the surface conditions on Earth? How have human activities affected its concentration in our atmosphere? Answer

Q3.  How does the greenhouse effect work to trap heat? Why is a change in wavelength of light important to the process? Answer

Q4.  Where is most of the CO2 in Earth? How did it get there? Answer

Q5.  Why would a rise in the amount of carbon dioxide (CO2) in Earth's atmosphere lead to rising sea levels? Answer

Q6.  Why is the greenhouse effect a good thing in Earth’s atmosphere? In what way might it become a "bad" thing? Answer

Q7.  What are the two most important greenhouse gases in Earth’s atmosphere? Why is only one of them affected by human activity? Answer

Q8.  Even when on one initial variable is changed (like increased CO2 in the air), why is it difficult to predict (or model) long term climatic changes? Answer

saturnbutton1.JPG (21728 bytes)Ozone Questions

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Q1.  What is ozone? Why is important to us? What role do CFC’s play in affecting it? Answer

Q2.  Why are chloro-fluoro-carbons (such as Freon) more damaging to the ozone layer than other chlorine-containing molecules commonly used in modern society? Answer

Q3.  What is the role of ozone in Earth’s atmosphere? In what way have humans affected the ozone concentration in the atmosphere? Answer

Q4.  In what way has human activity affected the ozone concentration in our atmosphere? What material is responsible for this change? Why is it so damaging to the ozone? Answer





saturnbutton1.JPG (21728 bytes)Earth - Atmosphere Answers

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A1.  Earth’s atmosphere is made mostly of nitrogen and oxygen gases. The unusual part of this is the presence of free oxygen in the atmosphere. Free oxygen is very reactive, and should have disappeared long ago. Its presence suggests that some mechanism is continuously creating more oxygen for the atmosphere. Of course, that process is life. Photosynthesis by plants releases oxygen into the atmosphere.

A2.  As you move upward from the surface of Earth, the temperature cools for several kilometers before it reverse and begins to increase (in the stratosphere). This increase ultimately reverses into another decline in temperature, which in turn changes into an increase in temperature at high altitude. The net effect is that the temperature oscillates back and forth over a fairly narrow range of values.

A3.  Periodic climate changes are caused by an effect known as the Milankovich cycle. The combined effect of small changes in the eccentricity of Earth’s orbit around the sun, the precession or wobbling of Earth’s axis of rotation, and small changes in the tilt of Earth’s axis of rotation can cause the subtle changes in climate that lead to an ice age.

A4.  Even though carbon dioxide is the most abundant gas released in volcanic processes, it is not the most abundant gas in our atmosphere because it slowly dissolves in the liquid water on Earth and ultimately forms carbonate rocks. The existence of free oxygen in our atmosphere is purely a result of biological activity, specifically photosynthesis.

A5.  The original atmosphere of Earth was lost when the solar wind of the early sun stripped away all the gas from around Earth. A secondary atmosphere was slowly released by volcanoes as gases were released from the molten rock. Most of this gas is carbon dioxide, but it is gradually dissolved in the oceans and precipitates out as carbonate rock instead of building up in the atmosphere.

A6.  The 3 factors that must combine to send Earth’s climate into an ice age are: (1) precession, or a change in the direction Earth’s axis points in space; (2) nutation, or a slight wobble in the inclination of Earth’s axis of rotation with respect to the plane of its orbit; and (3) a slight change in the eccentricity or shape of its orbit around the sun.

A7.  Oxygen in Earth’s atmosphere is the result of biological activity on Earth. Plants release oxygen as a by-product of photosynthesis. Since oxygen so readily reacts with many different materials, it would quickly disappear if it were not constantly being replenished.

A8.  As you rise from the surface of Earth the temperature decreases until it reaches a local minimum at about 6 miles (10 km). The temperature then begins to increase up to about 35 miles (60 km), where it begins to decrease again. Finally at about 60 miles (100 km) it begins to increase again for the rest of the way up until it finally merges with the interplanetary medium.

A9.  From the surface upward, the layers in Earth’s atmosphere are: troposphere (distinguished by the water cycle, which controls our weather); stratosphere (distinguished by the ozone layer); mesosphere (the top of the greenhouse where CO2 radiates energy to space); and thermosphere (so thin it is easily heated by sunlight).

A10.  Venus’ surface is much hotter than Earth’s. The atmospheres of both planets cool with increasing altitude above the surface. Between sea level and about 75 km altitude, Earth’s atmosphere cools and heats in several layers. In the same span, Venus’ atmosphere becomes progressively cooler. At about 75 km they have both reached the same temperature.

A11.  Astronomers believe that dust and steam raised into the atmosphere by the impact of a large asteroid cooled the climate enough to cause the extinction of the dinosaurs and most other species 65 million years ago. Several lines of evidence point in this direction. The most persuasive is that the layer of rock deposited during that period, wherever it is found on Earth, is rich in the element iridium. Iridium is extremely rare on Earth, but is much more abundant in iron-rich meteorites.

A12.  The temperature of any object is determined by the balance of input energy and emitted energy. The temperature of the object rises or falls until the object is able to radiate as much energy as it receives. The sources of energy for our atmosphere are sunlight and heat leaving the surface of Earth from the interior. Each layer of the atmosphere heats up until it can radiate as much energy as it receives form the sun and the layers below.

A13.  Our atmosphere is composed primarily of nitrogen (78%) and oxygen (22%). While nitrogen is a common gas for an atmosphere, free oxygen molecules are quite unusual. Oxygen is a very reactive substance and normally is quickly consumed in reactions with other substances in the environment. Its presence in our atmosphere is the result of continual production of more oxygen by plant life on Earth. Without that production mechanism, our atmosphere would be quickly cleaned of all its free oxygen molecules.

saturnbutton1.JPG (21728 bytes)Green House Effect Answers

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A1.  Visible sunlight enters the car through the windows. This light is absorbed by the interior of the car, which therefore is slightly warmed. The warmer interior then radiates infrared light to get rid of this extra energy, in an attempt to return to its original temperature. The infrared light is not able to escape from the car because glass is opaque to infrared light. The interior of the car continues to warm up until everything inside the car, including the glass, is so warm that the outside of the car can radiate infrared energy at the same rate as energy enters the car.

A2.  Carbon dioxide is an efficient greenhouse gas. After visible light from the sun has warmed the surface, it will radiate infrared radiation back into the atmosphere. Carbon dioxide efficiently absorbs this infrared light, thus trapping the energy in the atmosphere. This causes the temperature of the atmosphere to increase compared to what it would have if there were no greenhouse effect.

Human activity has increased the amount of carbon dioxide in the atmosphere, primarily through the burning of fossil fuels and the destruction of green plant life. This has increased the level of the greenhouse effect, and thus has increased the average temperature of the Earth.

A3.  The greenhouse effect occurs when a substance allows visible light to enter an enclosure, but does not allow infrared light to escape from the enclosure. The visible light is at least partially absorbed inside the enclosure, warming it up. The heated material would then radiate more infrared energy to get rid of the extra heat, but since the infrared radiation is trapped inside the enclosure, the overall temperature of the enclosure increases. The change in wavelength is crucial, because it has to first penetrate and then be absorbed upon re-radiation from the ground.

A4.  Most of Earth’s CO2 is found in carbonate rocks, such as limestone. CO2 dissolves in liquid water and reacts there with minerals in the water to form rock as it collects on the bottom of the ocean. CO2 also is incorporated into animal skeletons which fall to the bottom of the ocean to form rock

A5.  An increase in the carbon dioxide content of our atmosphere would cause an increase in the green house effect that would raise the average temperature of Earth. As the temperature increase, more and more of the ice in the ice caps will melt, which will slowly raise the level of water in the oceans.

A6.  If there were no greenhouse effect in our atmosphere, the temperature on the surface of Earth would be much colder than it is, to the point that life would probably not survive or would survive only in limited regions and species. However, if human activity continues to increase the greenhouse gases in the atmosphere, the effect might increase until the temperature becomes significantly hotter than it now is, creating a host of meteorological and environmental effects.

A7.  The 2 most important greenhouse gases in our atmosphere are water and carbon dioxide, with methane a distant third. However, the amount of water which can be present in the atmosphere is limited. When the relative humidity reaches 100 %, the water condenses into drops and falls to the ground as rain or snow. Thus, human activity cannot significantly affect the amount of water in the atmosphere. Burning of fuels can increase the amount of carbon dioxide in the atmosphere indefinitely, since it does not precipitate out of the atmosphere.

A8.  Predictions of climate effects are difficult to make because changes in the atmosphere are strongly interconnected to other changes. For example, if the CO2 content of the atmosphere increases, the direct effect is that the temperature rises to the increased greenhouse effect. However, that increased temperature may increase evaporation of water, which will increase the greenhouse effect. However, the increased water in the atmosphere may also increase cloud cover, which reflects more sunlight and cools the atmosphere. So it is possible that increasing the CO2 may either increase or decrease the temperature, depending upon how these various effects (and others) interact.

saturnbutton1.JPG (21728 bytes)Ozone Answers

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A1.  Ozone is a molecule with three atoms of oxygen in it, instead of the more normal two atoms of oxygen in an oxygen molecule. Ozone is important to us because it absorbs most of the ultraviolet radiation of the sun before it reaches the surface of Earth. When CFC’s are released into the atmosphere, they eventually rise to the stratosphere, where they begin to break down the ozone. This process decreases the amount of ozone in that protective layer of the atmosphere.

A2.  Chloro-fluoro-carbons are dangerous because of their chemical stability. When they are released into the lower atmosphere, they do not react with any other materials in their environment. As they slowly mix to higher and higher levels of the atmosphere, they finally are exposed to ultraviolet radiation, which breaks apart the molecules and releases chlorine atoms. Other chlorine-containing molecules released into the environment react with other compounds in the lower atmosphere and get cleaned out before they can reach the upper levels.

A3.  Ozone is responsible for absorbing the vast majority of the ultraviolet light from the sun, thus protecting plants and animals on the surface from this damaging radiation. When human activity release chlorofluorocarbons into the atmosphere, they slowly rise into the stratosphere, where they interact with the ozone. This increased destruction of ozone decreases the amount of ozone in the atmosphere. This effect is most prominent over Antarctica.

A4.  Human activity has added a new compound to the atmospheres that breaks down ozone into the more normal oxygen molecules, thus decreasing the amount of ozone in the stratosphere. These compounds are known as chlorofluorocarbons. The trade name of some of these compounds is freon. Since it is a very stable material, once it is released into the atmosphere, it remains for a very long time. When it finally reaches the ozone layer, it reacts with sunlight to release chlorine atoms which devour ozone molecules and prevent them from reforming. This depletes the ozone in the atmosphere, which allows more of the sun’s ultraviolet light to reach the surface.