Skip to main content
Home

Earth Resources Observation and Science (EROS) Center

Main Menu

  • EROS Home
  • Image Gallery
  • Video Library
  • Earthshots
  • Remote Sensing Classroom

Earthshots

  • Earthshots
    • Selkirk Island, Chile
      • More Selkirk Cloudscapes
      • Rare Clear Views
      • A Note on the Images
      • Reflectivity of Water
      • Other Vortices
  • Download Cards
  • More Information
  • Contact Information
Earthshots Logo

Selkirk Island, Chile

Coasts  / 
Water
  1. Earthshots
  2. Selkirk Island, Chile
Description

In September 1999, engineers at EROS were reviewing Landsat 7 sensor output. An image grabbed their attention. Over Selkirk Island, about 500 miles off the coast of Chile, they noticed an unusual cloud pattern. They referred the image to EROS scientists, who identified the striking series of swirls as a “Karman vortex street,” a fluid flow pattern rarely seen so clearly outside of a laboratory.

How did these Karman vortices develop? Selkirk Island is the tip of a volcanic peak, rising sharply from the ocean, its steep sides critical to the formation of these vortices. Though covering only 33 square miles, the island rises over a mile into the sky.

On the day Landsat 7 acquired this image, the wind was carrying northward a layer of stratocumulus clouds (flat-bottomed puffballs). The mile-high island caused this cloud layer to slow about the island, while remaining fast farther out on either side. So on each “wing,” left and right, the air started rotating toward the inside—clockwise on the left, counter-clockwise on the right. The rotational momentum made each side swirl in on itself.

The whorl-cores were clear because the swirling pulled dry, clear air (from above or below) into the wet layer, a bit like the funnel formed when you stir up a pitcher of orange juice. These clear, spinning pockets trailed off down the “street” from the island like soap bubbles from a toy wand—drifting downwind, weakening, filling with clouds, and breaking up.

We ordinarily show as few clouds as possible in Earthshots because they block our view of the land, but in this case they do have scientific, as well as aesthetic, value. The American Meteorological Society featured the Selkirk image on the cover of their monthly bulletin. This image also became one of the earliest selections in the Earth As Art collection.

View Related Imagery & Stories

Location

Sept. 15, 1999, Landsat 7 (path/row 6/83) — Selkirk Island vortex street

Sept. 15, 1999, Landsat 7 (path/row 6/83) — Selkirk Island vortex street

Sept. 15, 1999, Landsat 7 (path/row 6/83) — close up of Selkirk Island vortex street

Sept. 15, 1999, Landsat 7 (path/row 6/83) — close up of Selkirk Island vortex street

Sept. 15, 1999, Landsat 7 (path/row 6/83) — Selkirk Island vortex street
Sept. 15, 1999, Landsat 7 (path/row 6/83) — close up of Selkirk Island vortex street

Selkirk Island, Chile Additional Imagery & Stories

A Note on the Images
A Note on the Images

The Landsat images that are shown on Earthshots are combinations of three different wavelengths of the electromagnetic spectrum. Typically, the images...

Read More
More Selkirk Cloudscapes
More Selkirk Cloudscapes

Since its launch in 1999, Landsat 7 has not again seen such nice vortices over Selkirk Island. A single vortex formed on March 25, 2000, from a simila...

Read More
Other Vortices
Other Vortices

Selkirk Island is not the only place where Landsat has seen vortex streets. Other places where this phenomenon is common are nearby Robinson Crusoe Is...

Read More
Rare Clear Views
Rare Clear Views

April 19, 2009, could have been a rare clear view of the island, but some of the data are missing because of Landsat 7’s Scan Line Corrector (SLC) mal...

Read More
Reflectivity of Water
Reflectivity of Water

Have you noticed that in these images, clouds look white but the ocean looks black? Both are made of the same substance, water—why would they appear a...

Read More

References

References (Earthshot Overview/Parent Only)

DeFelice, T.P., Meyer, D.J., Xian, G., Christopherson, J., and Cahalan, R., 2000, Landsat-7 Reveals More Than Just Surface Features in Remote Areas of the Globe: Bulletin of the American Meteorological Society, v. 81, no. 5, p. 1047–1049. (Also available online at https://www.jstor.org/stable/e26215146.) 

  • DOI Privacy Policy
  • Legal
  • Accessibility
  • Site Map
  • Contact USGS

  • U.S. Department of the Interior
  • DOI Inspector General
  • White House
  • E-gov
  • No Fear Act
  • FOIA