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Chapter 15 The Atmosphere Page 450 The Atmosphere Thin layer of air that forms a protective covering around the planet! Functions/Benefits Absorbs and traps heat from the sun Without it, days would be extremely hot & nights would be extremely cold! Protects life from harmful ultra violet (UV) rays Provides living things with necessary gases such as oxygen Transports & Recycles water Properties Composition Air Pressure Relative Humidity Temperature Composition or Makeup of the Atmosphere Mixture of gases, solids, & liquids Extends from the surface of Earth to outer space Has changed over time! No oxygen on early earth. Oxygen began to form from cyanobacteria (tiny photosynthetic microorganisms) Ozone layer (O3) formed which allowed life to move onto land. Gases in the Atmosphere Nitrogen Oxygen (N2) – 78% (O2) – 21% Water Vapor – 4% Argon - .93% Carbon Trace Dioxide - .03% Elements: Neon, Helium, Methane, Hydrogen gas The Layers of the Atmosphere Troposphere Stratosphere Mesosphere Thermosphere Exosphere Atmospheric Pressure Gases have mass. Hundreds of miles of gas above Earth's surface Earth's gravity pulls the gases toward its surface creating pressure That pressure is called air pressure! Atmospheric Pressure Air pressure increases as you get closer to earth. Which layer has the highest air pressure? Troposphere Directly above the ground (crust) Extends 11 km or 7 miles up into the air Contains 75% of the atmospheric gases Including the oxygen we breath ¾ of the atmospheric mass Contains the Weather Gets colder the higher you go Most of the heat comes from the ground Stratosphere Layer above the troposphere 11 to 50 km (7-31 miles) Max Temperature = -3oc or 27oF Contains the Ozone Layer!!!! The Ozone Layer Ozone is comprised of three oxygen molecules (O3) The ozone layer shields us from UV radiation UV radiation can damage DNA So what? Please Save The Ozone Layer! Ultraviolet radiation can damage DNA Damage DNA = mutation Damaged DNA can lead to skin cancer. The Hole in The Ozone Layer Chlorofluorocarbons (CFCs) used in refrigerators, air conditioners, and aerosols Destroy Ozone Hole over Antarctica Page 472 The hole in the ozone was one of the most important problems in the 80s… Fortunately, most countries banned CFCs by the 1990s due to the Montreal Protocol! The Layers of the Atmosphere Troposphere Stratosphere Mesosphere Thermosphere Exosphere Mesosphere & Thermosphere Meso means middle Thermosphere Named due to its high temperatures (getting closer to the sun) Thickest layer 85 to 500 km Ionosphere – layer of eclectically changed particles (Northern Lights) Changes to the atmosphere Increased Levels of Carbon dioxide released by burning fossil fuels. Oil, Natural Gas, & Coal The greenhouse effect Increased levels of these gases can cause the earth to get hotter! • Carbon Dioxide • Methane • Nitrogen Oxide • Ozone Smog Car exhaust gases & other emissions mix with oxygen in the presence of sunlight Creates a brown haze Smoke + Fog Air Air Pollution Pollutants Dust (animals, people, dirt) Soot (burning) Pollen Salt (ocean) The Clean Air Act Page 470 1st passes in 1963 Revised many times in order to set stricter standards for air quality & strengthen the government’s ability to enforce regulations. Measures air quality in an attempt to reduce emission of pollutants that cause health problems such as asthma and cancer.