Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html">permafrost</a> in the <a href="/earth/polar/polar_north.html">Arctic</a> is extremely sensitive to sunlight.  Exposure to sunlight releases carbon gases trapped in the permafrost, including <a href="/earth/climate/earth_greenhouse.html">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p><p>Something on Earth is always burning! NASA's Earth Observatory tracks wildfires across the world with <a href="http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD14A1_M_FIRE" target="_blank">maps available for viewing</a> from 2000-present. Some wildfires can restore <a href="/earth/ecosystems.html">ecosystems</a> to good health, but many can threaten human populations, posing a natural disaster threat.</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 spinning vortex of <a href="https://www.windows2universe.org/saturn/saturn.html">Saturn</a>'s north polar storm resembles a giant deep red rose surrounded by green foliage in this false-color <a href="http://www.nasa.gov/mission_pages/cassini/multimedia/pia14944.html">image</a> from NASA's <a href="https://www.windows2universe.org/missions/cassini.html">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="https://www.windows2universe.org/earth/Atmosphere/hurricane/hurricane.html">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>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><p>You don't normally see <a href="/space_weather/space_weather.html">space weather</a> forecasted on the evening news, but it does impact life on <a href="/earth/earth.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">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>Stars don't last forever. Occasionally, a star bigger than our Sun will end its life in a huge explosion, called a <a href="/the_universe/supernova.html">supernova</a>. The center of the star collapses in less than a second, blowing away the outer layers of the star.  There are many beautiful images of supernova remnants, the expanding shell of gas made up of the outer layers of the original star. This image is the Vela Supernova Remnant.<p><small><em>Image courtesy of the Anglo-Australian Observatory/Royal Observatory Edinburgh</em></small></p>

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