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Become a nitrogen atom in the nitrogen cycle in our Traveling Nitrogen Classroom Activity Kit/Game. See all our games, activity kits and classroom activities.
There are over 900 <a href="/the_universe/uts/megalith.html&edu=elem">rings of stone</a> located in the British Isles. The most famous of these stone rings is of course, <a href="/the_universe/uts/stonehenge.html&edu=elem">Stonehenge</a>.    The stones of Stonehenge were put in place between 3,000 B.C and 2,000 B.C. by neolithic people.Some speculate that the site was built as a temple of worship of the ancient Earth deities. Some say it was used as an <a href="/the_universe/uts/stonehenge_astro.html&edu=elem">astronomical observatory</a> of sorts. Still others say it was a burial ground.<p><small><em>  Image courtesy of Corel Photography.</em></small></p>The spinning vortex of <a href="">Saturn</a>'s north polar storm resembles a giant deep red rose surrounded by green foliage in this false-color <a href="">image</a> from NASA's <a href="">Cassini spacecraft</a>. The eye is 2,000 kilometers across with cloud speeds as fast as 150 meters per second.
It is not known how long this newly discovered north-polar <a href="">hurricane</a> has been active.
The view was acquired at a distance of approximately 419,000 kilometers from Saturn.<p><small><em>NASA/JPL-Caltech/SSI</em></small></p>This first global map of <a href="">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="">Salinity</a> variations are one of the main drivers of <a href="">ocean circulation</a>, and are closely connected with the <a href="">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>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>Sinkholes are <a href="/teacher_resources/main/frameworks/esl_bi8.html&edu=elem">natural hazards</a> in many places around the world. They are formed when water dissolves underlying <a href="/earth/Water/carbonates.html&edu=elem">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>An <a href="">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">earthquake</a> and <a href="/earth/tsunami1.html&edu=elem">tsunami</a> processes. Check out the resources <a href="/teacher_resources/2011_AGU-NESTA_GIFT_Workshop.html&edu=elem">here</a>.<p><small><em>NOAA</em></small></p>

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA