Earth's Atmosphere

The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds Earth. High above the planet, the atmosphere becomes thinner until it gradually reaches space. It is divided into five layers. Most of the weather and clouds are found in the first layer.

The atmosphere is an important part of what makes Earth livable. It blocks some of the Sun's dangerous rays from reaching Earth. It traps heat, making Earth a comfortable temperature. And the oxygen within our atmosphere is essential for life.

Over the past century, greenhouse gases and other air pollutants released into the atmosphere have been causing big changes like global warming, ozone holes, and acid rain.

<a
  href="/earth/Atmosphere/tstorm/tstorm_lightning.html&edu=elem&dev=1">Lightning</a>
  is the most spectacular element of a <a
  href="/earth/Atmosphere/tstorm.html&edu=elem&dev=1">thunderstorm</a>.
  A single stroke of lightning can <a
  href="/earth/Atmosphere/temperature.html&edu=elem&dev=1">heat</a>
  the air around it to 30,000 degrees Celsius (54,000 degrees Fahrenheit)! This
  extreme heating causes the air to expand explosively. The expansion creates a
  shock wave that turns into a booming <a
  href="/earth/Atmosphere/tstorm/lightning_thunder.html&edu=elem&dev=1">sound
  wave</a>, better known as thunder.<p><small><em> Image Courtesy of University Corporation for Atmospheric Research/Carlye Calvin</em></small></p><a href="/earth/Atmosphere/NLC.html&edu=elem&dev=1">Noctilucent</a>
  clouds are the highest clouds in the sky, but they are not associated with
  weather like the <a
  href="/earth/Atmosphere/clouds/cloud_types.html&edu=elem&dev=1">other
  clouds</a> we regularly see in the sky. Noctilucent clouds form very high in
  the <a href="/earth/Atmosphere/overview.html&edu=elem&dev=1">atmosphere</a>,
  in the <a
  href="/earth/Atmosphere/mesosphere.html&edu=elem&dev=1">mesosphere</a>.
  They are best seen from Earth at sunset. This image was taken on June 15,
  2007, in Budapest, Hungary. Normally seen from locations near the <a
  href="/earth/polar/polar.html&edu=elem&dev=1">poles</a> of
  the Earth, in recent years they have also been seen at much lower-latitude
  locations.<p><small><em> Image Courtesy of NASA/Veres Viktor</em></small></p>Greenland's <a href="http://www.windows2universe.org/earth/polar/cryosphere_glacier1.html">ice sheet</a> saw a record <a href="http://www.windows2universe.org/headline_universe/olpa/greenland_10dec07.html">melt</a> in July 2012.  Scientists studying this event have found that this melting event was triggered by an influx of unusually warm air and amplified by the presence of a blanket of thin low-level <a href="http://www.windows2universe.org/earth/Atmosphere/cloud.html">clouds</a> which pushed temperatures up above freezing.  For more information see the <a href="http://www.news.wisc.edu/21638">press release</a> from the University of Wisconsin Madison.<p><small><em>Image courtesy of University of Wisconsin-Madison</em></small></p>An image of Hurricane Sandy taken by the GOES-13 satellite on October 28.  This category 1 <a href="/earth/Atmosphere/hurricane/hurricane.html&edu=elem&dev=1">hurricane</a> was huge, spanning a horizontal distance of about one-third the US continental landmass.  The storm came onshore in New Jersey, and gradually moved northeast.  The storm disrupted the lives of tens of millions in the eastern US, doing billions of dollars in damage, resulting in over 30 deaths.  Visit the National Hurricane Center's webpage on <a href="http://www.nhc.noaa.gov/">Hurricane Sandy</a> for details.<p><small><em>Image courtesy of NASA</em></small></p><a
  href="/earth/Atmosphere/clouds/lenticular.html&edu=elem&dev=1">Lenticular
  clouds</a> form on the downwind side of mountains. <a
  href="/earth/Atmosphere/wind.html&edu=elem&dev=1">Wind</a>
  blows most types of clouds across the sky, but lenticular clouds seem to stay
  in one place. Air moves up and over a mountain, and at the point where the
  air goes past the mountaintop the lenticular cloud forms, and then the air <a
  href="/earth/Water/evaporation.html&edu=elem&dev=1">evaporates</a>
  on the side farther away from the mountains. This close up of lenticular
  clouds was taken at sunset on November 20, 2006 in Boulder, Colorado.<p><small><em>       Courtesy of Roberta Johnson</em></small></p>How did life evolve on <a href="/earth/earth.html&edu=elem&dev=1">Earth</a> during the <a href="/earth/past/Archean.html&edu=elem&dev=1">Archean</a>, when the <a href="/sun/sun.html&edu=elem&dev=1">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&edu=elem&dev=1">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&edu=elem&dev=1">greenhouse</a> gas concentration was the same as today.  <a href="http://www.manchester.ac.uk/aboutus/news/display/?id=10798">Researchers</a> studying the <a href="/physical_science/physics/atom_particle/isotope.html&edu=elem&dev=1">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&edu=elem&dev=1">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&edu=elem&dev=1">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&edu=elem&dev=1">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=elem&dev=1">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>

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