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.

The massive 9.0 magnitude <a href="/earth/geology/quake_1.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">earthquake</a> off of Honshu, Japan on <a href="/headline_universe/march112011earthquaketsunami.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">11 March 2011</a> generated a <a href="/earth/tsunami1.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">tsunami</a> that exceeded 10 meters on the coast near the epicenter.  This image shows model projections for the tsunami wave height in cm which are in good agreement with the observed waves. Our thoughts and prayers are with those who were lost, and their families, as we remember this event.<p><small><em><a href="http://blogs.agu.org/wildwildscience/files/2011/03/680_20110311-TsunamiWaveHeight.jpg">NOAA Tsunami Wave Height Projections image</a></em></small></p>This first global map of <a href="http://www.windows2universe.org/earth/Water/ocean.html">ocean</a> surface saltiness, released in September 2012 by the NASA Aquarius mission team, shows the distribution of salt in the first 2 cm of the Earth's ocean. <a href="http://www.windows2universe.org/earth/Water/salinity.html">Salinity</a> variations are one of the main drivers of <a href="http://www.windows2universe.org/earth/Water/circulation1.html">ocean circulation</a>, and are closely connected with the <a href="http://www.windows2universe.org/earth/Water/water_cycle.html">cycling of freshwater</a> around the planet. High salinity is seen in the Mediterranean, Atlantic, and the Arabian Sea.<p><small><em>Image courtesy of NASA/GSFC/JPL-Caltech</em></small></p><p>You don't normally see <a href="/space_weather/space_weather.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">space weather</a> forecasted on the evening news, but it does impact life on <a href="/earth/earth.html&dev=1/earth/Atmosphere/moons/privacy_policy.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&dev=1/earth/Atmosphere/moons/privacy_policy.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>A view of the Earth as seen by the <a href="/space_missions/apollo17.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">Apollo
17</a> crew
while traveling to the
<a href="/earth/moons_and_rings.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">Moon</a> on
December 7, 1972.  Africa, Madagascar, and the Arabian Peninsula are
visible, and you can barely make out the
<a href="/earth/polar/antarctica.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">Antarctic</a>,
shrouded in the heavy
<a href="/earth/Atmosphere/cloud.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">cloud</a> cover
in the southern hemisphere.
Arching cloud patterns show the presence of <a href="/earth/Atmosphere/front.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">weather
fronts</a>.<p><small><em>Image courtesy of NASA/Apollo 17.</em></small></p>Coral animals build reefs in warm, tropical seawater. However, <a href="/earth/changing_planet/ocean_temperatures_intro.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">seawater can be too warm</a> for their liking.  If waters get too warm, coral animals lose the algae that live within their little bodies, a process called coral bleaching. Without the algae, corals have less nutrition. Unless cooler temperatures return, allowing algae to
 return, the coral dies.<p><small><em>Credit: UNC</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&dev=1/earth/Atmosphere/moons/privacy_policy.html">full phase</a>. Secondly, the <a href="/sun/sun.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">Sun</a>, <a href="/earth/earth.html&dev=1/earth/Atmosphere/moons/privacy_policy.html">Earth</a> and <a href="/earth/moons_and_rings.html&dev=1/earth/Atmosphere/moons/privacy_policy.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>

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