Anti-crepuscular rays are beams of sunlight that appear to converge on a point opposite the sun. They are similar to crepuscular rays, but are seen opposite the sun in the sky. Anti-crepuscular rays are most frequently visible near sunrise or sunset. This photo of anti-crepuscular rays was taken at sunset in Boulder, Colorado. Crepuscular rays are usually much brighter than anti-crepuscular rays.<p><small><em> Image Courtesy of Carlye Calvin</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">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>The massive 9.0 magnitude <a href="/earth/geology/quake_1.html">earthquake</a> off of Honshu, Japan on <a href="/headline_universe/march112011earthquaketsunami.html">11 March 2011</a> generated a <a href="/earth/tsunami1.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>Sinkholes are <a href="/teacher_resources/main/frameworks/esl_bi8.html">natural hazards</a> in many places around the world. They are formed when water dissolves underlying <a href="/earth/Water/carbonates.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>According to <a href="http://www.jpl.nasa.gov/news/news.php?release=2013-277">NASA scientists</a>, the Voyager 1 spacecraft entered interstellar space in August 2012, becoming the first spacecraft to leave the <a href="/our_solar_system/solar_system.html">solar system</a>. The space probe is about 19 billion km from the <a href="/sun/sun.html">Sun</a>. <a href="/space_missions/voyager.html">Voyager 1 and 2</a> were launched in 1977 on a <a href="/space_missions/voyager.html">mission</a> that flew them both by <a href="/jupiter/jupiter.html">Jupiter</a> and <a href="/saturn/saturn.html">Saturn</a>, with Voyager 2 continuing to <a href="/uranus/uranus.html">Uranus</a> and <a href="/neptune/neptune.html">Neptune</a>. Voyager 2 is the longest continuously operated spacecraft. It is about 15 billion km away from the <a href="/sun/sun.html">Sun</a>.<p><small><em>Image courtesy of NASA</em></small></p>How did life evolve on <a href="/earth/earth.html">Earth</a> during the <a href="/earth/past/Archean.html">Archean</a>, when the <a href="/sun/sun.html">Sun</a> was about 25% weaker than today? The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.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">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>


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Oceanographers are using robotic undersea "gliders" to study "dead zones" in the seas. View this video from the National Science Foundation ...Read more
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Video: Beaufort Scale of Wind Speeds

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Modeling Space Weather

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Galileo Galilei

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Groundwater

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