Earth

Earth, our home planet, is a beautiful blue and white ball when seen from space. The third planet from the Sun, it is the largest of the inner planets. Earth is the only planet known to support life and to have liquid water at the surface. Earth has a substantial atmosphere and magnetic field, both of which are critical for sustaining life on Earth. Earth is the innermost planet in the solar system with a natural satellite – our Moon. Explore our beautiful home planet – unique in our solar system - through the links in this section.

As permafrost thaws, the land, atmosphere, water resources, ecosystems, and human communities are affected. Coastal areas and hillsides are vulnerable to erosion by thawing of permafrost.  Thawing permafrost also causes a positive feedback to global warming, as carbon trapped within the once-frozen soils is released as <a href="/physical_science/chemistry/methane.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">methane</a>, a powerful <a href="/earth/climate/cli_greengas.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">greenhouse gas</a>.
Watch the NBC Learn video - <a href="/earth/changing_planet/permafrost_methane_intro.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Thawing Permafrost and Methane</a> to find out more.<p><small><em>Image courtesy of the    USGS</em></small></p>How did life evolve on <a href="/earth/earth.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Earth</a> during the <a href="/earth/past/Archean.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Archean</a>, when the <a href="/sun/sun.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">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/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>Lunar eclipses are special events that only occur when certain conditions are met. First of all, the Moon must be in <a href="/the_universe/uts/moon3.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">full phase</a>. Secondly, the <a href="/sun/sun.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Sun</a>, <a href="/earth/earth.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Earth</a> and <a href="/earth/moons_and_rings.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Moon</a> must be in a perfectly straight line. If both of these are met, then the Earth's shadow can block the Sun's light from hitting the Moon.  The reddish glow of the Moon is caused by light from the Earth's limb scattering toward the Moon, which is reflected back to us from the Moon's surface.<p><small><em>Image credit - Doug Murray, Palm Beach Gardens, Florida</em></small></p>Sinkholes are <a href="/teacher_resources/main/frameworks/esl_bi8.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">natural hazards</a> in many places around the world. They are formed when water dissolves underlying <a href="/earth/Water/carbonates.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">limestone</a>, leading to collapse of the surface.  Hydrologic conditions such as a lack of rainfall, lowered water levels, or excessive rainfall can all contribute to sinkhole development. On 2/28/2013, a sinkhole suddenly developed under the house outside of Tampa, Florida, leading to the tragic death of its occupant, Jeff Bush.<p><small><em>Image courtesy of Southwest Florida Water Management District</em></small></p><p>You don't normally see <a href="/space_weather/space_weather.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">space weather</a> forecasted on the evening news, but it does impact life on <a href="/earth/earth.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">Earth</a> in many ways. What are the threats posed from all of these natural disasters and how can we work to mitigate those threats beforehand? </p>
<p>Check out the materials about natural disasters in <a href="/earth/natural_hazards/when_nature_strikes.html&edu=elem&dev=1/earth/Atmosphere/moons/h/neptune/k=/teacher_resources/games_space_sense.html">NBC Learn Videos</a>, and their earth system science connections built up by the related secondary classroom activities.</p><p><small><em>NBC Learn</em></small></p>This image is a montage of high resolutions photographs of the Earth taken in January 2012 by the Visible/Infrared Imager Radiometer Suite (VIIRS) instrument on the Suomi NPP satellite.  The image shows many stunning details of <a href="http://www.windows2universe.org/earth/earth.html">our home planet</a> - <a href="http://solarsystem.nasa.gov/multimedia/gallery/VIIRS_4Jan2012.jpg">particularly at high resolution</a>. The beauty of our planet is obvious from space - our blue <a href="http://www.windows2universe.org/earth/Water/overview.html">waters</a>, our white <a href="http://www.windows2universe.org/earth/Atmosphere/cloud.html">clouds</a>, and the green from <a href="http://www.windows2universe.org/earth/Life/life.html">life</a> abundant at the surface.<p><small><em>Image courtesy of NASA</em></small></p>

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