This is an awesome picture. Supercell Thunderstorm by Sean Heavey, nationalgeographic: A supercell thunderstorm rolls across the Montana prairie at sunset. This was a winning shot in the 2010 National Geographic Nature Gallery Photo Contest.
The Cordón Caulle volcano in central Chile is pictured in all it's glory by Chilean photographer Francisco Negroni. His stunning snaps show forks of volcanic lightning to create an incredible light show.