Volcanoes, Vog, And Vortices • Earth.com

Last update: August 21st, 2019 at 2:00 am

Astronauts aboard the International Space Station oriented the camera specifically to capture this panorama of Hawaii’s Kilauea volcano with long swirls of volcanic gases wafting to the west. Astronauts are trained to take images of hard-to-see atmospheric haze by shooting obliquely to enhance visibility.

The haze, or “vog”—a combination of fog, smog, and volcanic gas—is well known to Hawaiians. Vog is scientifically defined as “a visible haze comprised of gas and an aerosol of tiny particles and acidic droplets, created when sulfur dioxide and other gases chemically interact with sunlight and atmospheric oxygen, moisture, and dust.” (Hawaiian Volcano Observatory).

In this photograph, the vog haze is transported hundreds of kilometers downwind of the volcano; for scale, the Big Island of Hawaii is 137 kilometers (85 miles) long. The vog forms a series of subtle, but distinct alternating swirls known as von Kármán vortices, a favorite subject for astronaut photography. Click here to view an animation of alternating vortices being shed from an island can be seen here. These vortices form under specific conditions of high atmospheric pressure and relatively slow wind speeds. They usually show up in clouds downwind of islands, as shown in this astronaut photo of cloud patterns over the Kuril Island chain. Images of vog haze are captured often by astronauts, but few show the von Kármán phenomenon.

NASA

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