Cumulonimbus Cloud over Africa
Perhaps the most impressive of cloud formations, cumulonimbus (from the Latin for “pile” and “rain cloud”) clouds form due to vigorous convection (rising and overturning) of warm, moist, and unstable air. Surface air is warmed by the Sun-heated ground surface and rises; if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes.
After 10 months of relative quiet, Soufriere Hills volcano on the Caribbean island of Montserrat blasted ash into the sky in early October 2009. This natural-color satellite image shows a plume of ash extending westward from Soufriere Hills on October 6, 2009, a day after eruptive activity resumed on October 5th. According to the U.S. Air Force Weather Agency, ash extended 280 kilometers (170 miles) at an elevation of approximately 3,600 meters (12,000 feet).
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APIA, SAMOA – OCTOBER 03: An aerial view of the devastaion along the South East coastline of Samoa is seen following the 8.3 magnitude strong earthquake which struck 200km from Samoa’s capital Apia on Tuesday, on October 3, 2009 in Apia, Samoa. The quake triggered a tsunami wave up to 1.5 metres across areas of the island, with the official death toll in Samoa standing at 149. A further quake measuring 6.3 struck 85 kilometres south-east of Tonga, but no tsunami warning or additional casualties have been reported as yet. (Photo by Phil Walter/Getty Images)
The flooding around Atlanta this week is one for the record books. According to the U.S. Geological Survey (USGS), the rivers and streams had magnitudes so great that the odds of it happening were less than 0.2 percent in any given year. In other words, there was less than a 1 in 500 chance that parts of Cobb and Douglas counties were going to be hit with such an event.
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NIAS, INDONESIA – MARCH 31: Boys make their way around the eartquake cracked streets during rescue operations March 31, 2005 in Gnung Sitoli, Nias, Indonesia. An earhquake measured 8.7 on the Richter scale hit the South East Asian region of Sumatra at 11:09 pm local time on March 28 and reportedly lasted 2 minutes. The island of Nias off the coast of Sumatra was the hardest hit with the death toll estimated at two thousand people. (Photo by Daniel Berehulak/Getty Images)