Presentation on theme: " The atmosphere is a layer of gases that surround the Earth. These layers differ in temperature, in density, and in the relative amounts of the different."— Presentation transcript:
The atmosphere is a layer of gases that surround the Earth. These layers differ in temperature, in density, and in the relative amounts of the different gases that are present. The two main gases in the atmosphere are nitrogen and oxygen. Nitrogen makes up about 70% of the atmosphere, Oxygen about 20%, and the rest is a mixture of various other gases such as Carbon Dioxide, Methane, Hydrogen, Neon, etc.
Layers of the Atmosphere troposphere stratosphere mesosphere thermosphere
Troposphere: the lowest layer Temperature drops as altitude increases The troposphere is the densest layer Almost all weather occurs in the troposphere.
stratosphere: between the troposphere and the mesosphere temperature increases as altitude increases; contains the ozone layer The ozone layer shields living things on Earth’s surface from ultraviolet- radiation damage.
mesosphere: the coldest layer of the atmosphere, temperature decreases as altitude increases Temperatures in the mesosphere decrease to about -80º C.
thermosphere: the uppermost layer of the atmosphere temperature increases as altitude increases Temperatures average about 980 °C (1,796 °F) because the small amount of oxygen absorbs intense solar radiation.
The ionosphere: the lower thermosphere and upper mesosphere When solar energy is absorbed, charged ions are formed. Radio waves are reflected in the ionosphere. Auroras take place in the ionosphere.
When Earth began to solidify, about 4.4 billion years ago, volcanic eruptions released a variety of gases. The gases released by volcanoes did not include oxygen.
Photosynthetic bacteria contribute oxygen to the atmosphere. Organisms evolved photosynthesis, a method of capturing energy from the sun. Photosynthesis produces oxygen as a waste product. Gradually the oxygen content increased to what it is today.
Animals produce carbon dioxide necessary for photosynthesis. Oxygen breathing organisms evolved and released carbon dioxide as a waste product. The oxygen-carbon dioxide cycle maintains a balance of atmospheric gases on Earth.
Human-made chemicals can deplete the ozone layer. Ozone forms when the sun’s ultraviolet rays strike molecules of O 2. Ozone absorbs much of the sun’s ultraviolet radiation. Without the ozone layer, ultraviolet radiation would damage living cells. Chlorofluorocarbons, CFCs, are chemicals that destroy the ozone layer, but are now banned in most countries.
greenhouse effect: the warming of the surface and lower atmosphere of Earth that occurs when carbon dioxide, water vapor, and other gases in the air absorb and reradiate infrared radiation Greenhouse gases trap the sun’s heat and keep Earth’s surface warm.
Too much carbon dioxide may cause global warming/climate change If too much energy is absorbed by the atmosphere, global temperatures will rise. Global warming could cause problems, such as rising ocean levels, because of melting polar icecaps, and droughts. Combustion of coal, oil, and gas has added more carbon dioxide to the air.