<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=high&dev=">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>On May 20, 2013, a massive EF5 <a href="http://www.windows2universe.org/earth/Atmosphere/tornado.html">tornado</a> hit Moore, Oklahoma, devastating communities and lives.  The tornado, on the ground for 40 minutes, took a path through a subdivision of homes, destroying block after block of homes, and hitting two elementary schools just as school was ending as well as a hospital. Hundreds of people were injured, and 24 were killed.<p><small><em>Image courtesy of Ks0stm, Creative Commons Attribution-Share Alike 3.0 Unported license</em></small></p>A near-Earth <a href="/our_solar_system/asteroids.html&edu=high&dev=">asteroid</a> - named 2012 DA14 by astronomers - passed within 17,200 miles from Earth on February 15, 2013. On closest approach at about 1:25 p.m. CST on February 15, although it was within the orbit of the <a href="/earth/moons_and_rings.html&edu=high&dev=">Moon</a> and even geosynchronous <a href="/space_missions/satellites.html&edu=high&dev=">satellites</a>, it didn't strike Earth!  Find out more from <a href="http://www.nasa.gov/mission_pages/asteroids/news/asteroid20130201315144.html">NASA</a>! Fragments of a meteorite hit Chelyabinsk, Russia on 2/15/2013 <a href="http://www.reuters.com/article/2013/02/15/us-russia-meteorite-idUSBRE91E05Z20130215">injuring over 500</a>. Learn about <a href="http://www.windows2universe.org/our_solar_system/meteors/meteors.html">meteors and meteorites</a>.<p><small><em>NASA/JPL-CalTech</em></small></p>Sinkholes are <a href="/teacher_resources/main/frameworks/esl_bi8.html&edu=high&dev=">natural hazards</a> in many places around the world. They are formed when water dissolves underlying <a href="/earth/Water/carbonates.html&edu=high&dev=">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>How did life evolve on <a href="/earth/earth.html&edu=high&dev=">Earth</a> during the <a href="/earth/past/Archean.html&edu=high&dev=">Archean</a>, when the <a href="/sun/sun.html&edu=high&dev=">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&edu=high&dev=">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&edu=high&dev=">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=high&dev=">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&edu=high&dev=">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&edu=high&dev=">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&edu=high&dev=">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=high&dev=">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>A <a href="http://iopscience.iop.org/1748-9326/8/2/024035/article">study</a> of over 40,000 written entries in Irish Annals and ice core measurements shows a strong correlation between <a href="http://www.windows2universe.org/earth/interior/eruptions.html">volcanic eruptions</a> and extreme cold weather in Ireland over a 1200 year period, from 431 to 1649.  During this time up to 48 volcanic eruptions were identified in Greenland ice core records through deposition of volcanic sulfate in annual layers of ice. Find out more about <a href="http://www.windows2universe.org/earth/climate/geosphere_volcanoes_influence_on_climate.html">volcanoes and climate</a>.<p><small><em>Image Courtesy of Marco Fulle</em></small></p>

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