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Volcanic Twilight Sky imaged by Ashley Bradford August 20, '08. Image ©Ashley Bradford, shown with permission.

Colourful sunsets and twilights are occurring over the United States.

They are probably caused by material from the eruptions of three stratovolcanoes in the Aleutian Islands.

Volcanoes loft vast tonnages of finely divided ash and sulfur oxide gases into the stratosphere. The sulfur gases subsequently produce aerosol particles.

The high altitude dust and aerosol scatters sunlight to give glorious sunsets, rays and Bishop's rings.