Image: Volcanic plume over Southern Atlantic revealed through false-color imagery

May 01, 2014
Credit: Jeff Schmaltz/MODIS Land Rapid Response Team, NASA GSFC

The South Sandwich Islands, in the far southern Atlantic Ocean, are often shrouded with thick cloud, making it difficult to view the region from space. Sometimes, however, the use of false-color imagery can be used to reveal events that would otherwise be obscured under cloud cover.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite flew over the South Sandwich Islands on April 19, 2014 and acquired this false-color image of the cloudy scene.

This false-color image uses a combination of non-visible (middle infrared and infrared) and visible (red) light captured in bands 7, 2, and 1, respectively, to distinguish clouds from snow and ice. Here the ice-covered islands appear bright turquoise, the clouds light turquoise and the water in the ocean appears deep black. Because the is a moist mixture of gas and ash, it reflects all three forms of light relatively well, so it appears nearly white.

In the north of this image, a thin of white rises from the volcano on Zavodovski island, the northernmost of the South Sandwich Islands and streams to the northeast. Further south, a wider white plume can be seen blowing across the Atlantic Ocean. This plume rises from the Mount Michael volcano, which is a young and frequently active stratovolcano located on Saunders Island, near the center of the South Sandwich Island chain.

The white plume from Mount Michael forms a chain of swirling eddies as it blows to the northeast. To the south, similar eddies can be seen behind three other islands. These are known as Von Kármán vortices. These vortices can form nearly anywhere that fluid flow is disturbed by an object. Because the atmosphere behaves like a fluid, when streaming air hits a blunt object, such as a mountain peak, the wind is forced around the object. The disturbance in the flow of the wind propagates downstream in a double row of vortices that alternate their direction of rotation, much like the eddies seen behind a pier in a river as water rushes past.

Explore further: Image: Volcanic smog and sunglint in the Vanuatu Archipelago

add to favorites email to friend print save as pdf

Related Stories

Cloud streets off of the Aleutian Islands

Jan 30, 2012

(PhysOrg.com) -- Strong winds polished the snow of southwestern Alaska and stretched marine stratocumulus clouds into long, parallel streets in early January, 2012. After crossing Bristol Bay, the winds scraped ...

Sandy streets over the Atlantic

Feb 10, 2012

Thick dust from the Sahara blowing over the ocean off the western coast of Africa encounters the islands of Cape Verde, forming a wake of swirling “vortex streets” visible by satellite.

Satellite looks down the eye of erupting Nabro Volcano

Jun 28, 2011

Wow! What an amazing and detailed top-down view of an active volcano! This is the Nabro Volcano, which has been erupting since June 12, 2011. It sits in an isolated region on the border between Eritrea and ...

Recommended for you

Methane is leaking from permafrost offshore Siberia

8 hours ago

Yamal Peninsula in Siberia has recently become world famous. Spectacular sinkholes, appeared as out of nowhere in the permafrost of the area, sparking the speculations of significant release of greenhouse ...

New discovery in Arctic is a very old clam

8 hours ago

The rapidly thawing Arctic Ocean may be a new frontier but some of the latest news from there concerns a clam that is believed to date back more than a million years.

Researchers on expedition to solve 'small island problem'

9 hours ago

Researchers from the Department of Electronic & Electrical Engineering are starting their new year with an expedition to the island of South Georgia to carry out research into improving weather forecasting. You can follow the team's progress on their blog. ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.