This is the rotating updraft base of a supercell thunderstorm, photographed in Kansas in May 2014.
Supercells, also known as rotating thunderstorms, are the least common type of thunderstorm.
This supercell formed south of the city of Climax, and lasted for two hours.
Professional storm chaser Stephen Locke took this series of photos.
"Kansas is often regarded as fly-over country, with nothing interesting to see," he said in a press release.
"But I have discovered that Kansas and other Great Plains offer something unique – supercell thunderstorms, the most powerful storms over land."
"They have now become the focus of my stills and motion pictures."
