Scientists are concerned that melting Arctic sea ice will increase the amount of fresh water in the <a href="/earth/polar/arctic_currents.html&edu=elem&dev=1/privacy_policy.html">Beaufort Gyre</a>, which could spill out into the Atlantic and cause major climate shifts in North America and Western Europe. Watch the <a href="/earth/changing_planet/freshwater_arctic.html&edu=elem&dev=1/privacy_policy.html">Changing Planet: Fresh Water in the Arctic video</a>.<p><small><em> Courtesy of Jack Cook, WHOI (<a href="http://www.whoi.edu">Woods Hole Oceanographic Institute</a>)</em></small></p><p>The United Nations <a href="http://reliefweb.int/sites/reliefweb.int/files/resources/PAND_report.pdf" target="_blank">estimated</a> that between 1994-2015, there were 6,873 natural disasters worldwide, which affected 218 million people and claimed 1.35 million lives. </p> <p>Check out the materials about natural disasters in <a href="/earth/natural_hazards/when_nature_strikes.html&edu=elem&dev=1/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>As temperatures rise and soil moisture decreases, plants are stressed, which can lead to <a href="/earth/climate/crops_withering.html&edu=elem&dev=1/privacy_policy.html">crop withering</a>. <a href="/teacher_resources/online_courses/health/events_health.html&edu=elem&dev=1/privacy_policy.html">Droughts</a> accompanied by increased temperatures can lead to famine, social and political disruptions. Scientists are helping with early identification of drought that might trigger food shortages. Watch the NBC Learn video - <a href="/earth/changing_planet/withering_crops_intro.html&edu=elem&dev=1/privacy_policy.html">Changing Planet: Withering Crops</a> to find out more.<p><small><em>Image taken by Tomas Castelazo, Creative Commons <a href=&quot;http://creativecommons.org/licenses/by/3.0/deed.en&quot;>Attribution 3.0 Unported</a> license.</em></small></p>An artist's rendering of the moment of impact of a massive <a href="/our_solar_system/meteors/meteors.html&edu=elem&dev=1/privacy_policy.html">meteorite</a> at the end of the Cretaceous (at the end of the <a href="/earth/geology/hist_mesozoic.html&edu=elem&dev=1/privacy_policy.html">Mesozoic Era</a>). Many scientists have concluded for decades that a meteorite four to six kilometers in diameter impacted the Earth at this time, resulting in a <a href="/earth/past/KTextinction.html&edu=elem&dev=1/privacy_policy.html">mass extinction of dinosaurs</a> and many other life forms. Recent research suggests that perhaps <a href="/headline_universe/olpa/chicxulub.html&edu=elem&dev=1/privacy_policy.html">massive volcanic eruptions</a> may be been responsible for the extinction.<p><small><em>Courtesy of Don Davis, NASA</em></small></p>An <a href="http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000905e.php">8.6 magnitude earthquake</a> struck on 11 April 2012 off of Banda Aceh, Sumatra, Indonesia, followed by a strong aftershock. Earthquake motion was primarily horizontal. A tsunami warning was issued for the Indian Ocean, but was cancelled at 12:36 UTC. A tsunami was observed at 1 meter or less. Find out more about <a href="/earth/geology/quake_1.html&edu=elem&dev=1/privacy_policy.html">earthquake</a> and <a href="/earth/tsunami1.html&edu=elem&dev=1/privacy_policy.html">tsunami</a> processes. Check out the resources <a href="/teacher_resources/2011_AGU-NESTA_GIFT_Workshop.html&edu=elem&dev=1/privacy_policy.html">here</a>.<p><small><em>NOAA</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/privacy_policy.html">full phase</a>. Secondly, the <a href="/sun/sun.html&edu=elem&dev=1/privacy_policy.html">Sun</a>, <a href="/earth/earth.html&edu=elem&dev=1/privacy_policy.html">Earth</a> and <a href="/earth/moons_and_rings.html&edu=elem&dev=1/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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