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Environmental Science Chapter 7 Notes #1 Atmosphere • Thin Layer of gases that surrounds the Earth • Extends from the surface to 100’s of km’s above • “Air” – Composition • 78% Nitrogen • 21% Oxygen • 1% = water vapor, argon, carbon dioxide, neon, helium, and others – 2 most important • Oxygen for respiration • Carbon Dioxide for photosynthesis Atmosphere • Living organisms appeared about 4 billion years ago – Changed out the atmosphere • Depleted the oxygen – Plant evolved to photosynthesize – Allowed for increased oxygen in the atmosphere • Photosynthesis and Respiration keep oxygen and carbon dioxide constant Atmosphere • Our atmosphere has 5 layers – The layers get less dense the further you move out from Earth’s surface • 1. Troposphere – – – – Nearest to Earth’s Surface Extends out to 10 km (6 mi) Where most weather occurs Contains 90% of the atmosphere’s gases Atmosphere 2. Stratosphere 1. 10 km to 50 km (about 30 mi) 2. Less dense than troposphere 3. Contains the ozone layer 1. Protects us from UV rays 4. Wind blows – not as much turbulence as in troposphere 3. Mesosphere 1. 50 km to 80 km (about 50 mi) 2. Less dense than the troposphere and the stratosphere Atmosphere 4. Thermosphere 1. 80 km to 500 km (310 mi) 2. Less dense than all three of the above 5. Exosphere 1. Beyond the thermosphere 2. Gases become thinner and thinner 3. It eventually just merges with outer space Climate • Weather – What is happening in the atmosphere at a particular place at a particular time • Climate – Average weather in an area over a long period of time Temp and precip. – Aspects of climate Generally determines what • Temperature type of organisms • Humidity are able to live in • Wind a particular region • Precipitation What Determines Climate? 1. Latitude 1. Distance from the equator 2. Measured in degrees N or S 3. Solar energy received depends on latitude 2. Air Circulation 1. 2. 3. 4. Cold air sinks and warms as it does so Warm are rises and cools as it does so Warm air holds more water than cold air As warm air rises it causes wind (mvmt of air) 5. End result – areas of heavy precipitation, dry areas, etc. What Determines Climate? 3. Ocean Currents 1. Currents redistribute large masses of hot and cold water 2. Mvmt cause by winds and rotation of the Earth 3. Oceans make climates more moderate (warm winters and cool summers) 4. Local Geography 1. Height above sea level affects temp 2. Mountains influence the distribution of precipitation Seasonal Change in Climate • Result in Earth’s orbit around the sun • In the Northern Hemisphere the Earth tilts so that we get more direct sunlight in the summer than in the winter • We are closest to the sun in the winter! • Equator gets direct sunlight year around – so its always warm (tropics) Seasonal Change in Climate