FINAL REVIEW SLIDES - The Atmosphere Evolves Our atmosphere...

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1 • Our atmosphere = the air (specific mix of gases) around us • Protects Earth from harmful solar radiation, and incoming projectiles. • Lower bound – touches surface of Earth • Upper bound – gradual transition into space • Observed from space the atmosphere is a thin shell around Earth The Good Earth/Chapter 14: The Atmosphere The Atmosphere Evolves • What is the atmosphere made of? ! Mostly Nitrogen and Oxygen ! CO 2 is a small component but plays a large role in the greenhouse effect ! Water vapor in the air can range from 0% over deserts to 7% in humid climates The Good Earth/Chapter 14: The Atmosphere Is the atmosphere of the Earth stable or is it changing with time? Why? The Atmosphere Evolves • Having an atmosphere is not unique to Earth, but our atmosphere’s composition is unique. ! Venus and Earth began with very similar atmospheres rich in carbon dioxide, hydrogen, and water vapor. ! The atmospheres originated from gases expelled from extensive volcanism and collision with comets/meteorites. ! Venus being closer to sun had abundant water vapor. This vapor was split into hydrogen and oxygen, and hydrogen was lost to space. Remaining oxygen bonded with carbon ! abundant CO 2 . ! CO2 blanket around Venus insulates planet ! 867°F on the surface! The Good Earth/Chapter 14: The Atmosphere The Atmosphere Evolves The Atmosphere Evolves Earth ! No oxygen present 4 billion years ago. -As early Earth cooled, water condensed, rained, removed CO2 from the atmosphere. -Early primitive organisms used photosynthesis to consume CO2 and produce oxygen. -Oxygen accumulated in oceans but not atmosphere until about 2 billion years ago (oxygen is reactive and combined with other elements in early rocks). Then land plants… Key Point: Life Came Before Free Oxygen in Earth’s Atmosphere Earliest animals lived in oceans. Oceans protected them from harmful solar radiation. Once oxygen accumulated in Earth’s atmosphere, life could be sustained on land. This is also when the ozone layer developed, protecting life on land from UV rays. Gravity holds 99% of atmospheric gases within 20 miles of the Earth’s surface • The density of air rapidly decreases with increasing altitude. • The accepted boundary with space is 62 miles above Earth’s surface. • Few gas molecules exist at that altitude. • Some gas must extend as high as 312 miles high, as spacecraft can feel drag up to this altitude. Structure and Processes of the Atmosphere • Atoms in water or air are constantly in motion = kinetic energy. Kinetic energy increases as speed of atomic motion increases Heat = the total kinetic energy of all the atoms in a substance Temperature = the average kinetic energy of all the atoms in a substance These pans of water are heated at the same rate for the same amount of time. They contain the same amount of heat , which is spread among the water molecules in each pan. But the water in pan 2 has a higher temperature , as the heat would have produced more rapid
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This note was uploaded on 05/08/2008 for the course NATS 101 taught by Professor Allister during the Spring '08 term at University of Arizona- Tucson.

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FINAL REVIEW SLIDES - The Atmosphere Evolves Our atmosphere...

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