Chapter 22: Earth’s Atmosphere

Ch 22-1: Characteristics of the Atmosphere The origin of the atmosphere When the Earth formed, it was too hot for an atmosphere As it cooled, first atmosphere contained Methane Ammonia no free oxygen First atmosphere driven off by outgassing from volcanoes carbon dioxide Water Vapor which condensed to form oceans

Early life, such as cyanobacteria (blue green algae) generated free oxygen through photosynthesis Animal life became possible after free oxygen was created Free oxygen in Earth’s atmosphere makes it unique

Earth’s current Atmosphere 78% Nitrogen 21% Oxygen 1% other gases

Effects on the composition of the atmosphere The Greenhouse Effect and Global Warming Carbon dioxide in the atmosphere traps heat energy in atmosphere like a greenhouse Trapped heat warms the Earth → leads to global warming

Ozone Depletion a. Ozone is a thin layer of O3 in the upper stratosphere which blocks UV light which damages living tissue b. Chlorofluorocarbons (CFC’s) break down ozone in a photochemical reaction (a chemical reaction caused by light)

CFC’s were banned and hole in Ozone has shrunk –an environmental success story CFCs were used in aerosol cans and as coolants in air conditioners and refrigerators

Natural influences on Earth’s Atmosphere Volcanic eruptions Ash and dust can prevent absorption of sunlight Earth cools Meteorite impacts can create dust and ash

Atmospheric Conditions Pressure the pressure exerted in all directions due to the weight of the atmosphere entire mass is within 32 miles of Earth’s surface Measuring pressure Mercurial barometer Aneroid barometer

Solar Energy Latitude- primary factor that influences amount of sunlight received and climate Equator receives most direct sunlight Poles receive more indirect sunlight

Circulation pressure differences cause movement of air air always moves from high to low pressure Coriolis effect rotation of the Earth causes moving object to travel in an apparent curved path Direction of curve depends on location Northern hemisphere- curves right Southern Hemisphere-curves left Coriolis Effect

Jet Streams- narrow bands of high speed winds in upper troposphere and lower stratosphere caused by density differences in heavy polar air and lighter air from mid-latitudes Influence weather globally Local winds Land and sea breezes Mountain and valley breezes