At a Glance: Coral Reefs

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 Atolls act as natural markers, encircling the places where now submerged volcanic islands once stood. 

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory.

All images, illustrations, and videos courtesy of NASA except:
·       Great Barrier Reef underwater video footage courtesy of Andy Green at
·       Photo of reef fishers courtesy of Rebecca Weeks/Marine Photobank
·       Sea creature illustration copyright The National Library of Israel, Shapell Family Digitization Project _and The Hebrew University of Jerusalem, Department of Geography – Historic Cities Research Project
·       Photo of fish at a coral reef courtesy of Linda Wade/NOAA
·       Photo of a dead reef in American Samoa copyright Wolcott Henry 2005/Marine Photobank
·       Photo of a bleached reef courtesy of Armando Jenik 2009/Marine Photobank
·       Staghorn coral photo courtesy of William Harrigan/Florida Keys National Marine Sanctuary/NOAA
·       Photo of coral in Perhentian Islands, Malaysia, courtesy of Nazir Amin
·       Mediterranean red coral photo courtesy of Lorenzo Bramanti/Marine Photobank
·       Gorgonian coral photo courtesy of Mohammed Al Momany/NOAA
·       Acropora table coral photo copyright Pete Faulkner, Mission:awareness/Marine Photobank 
·       Sewage pipe photo courtesy of Steve Spring/Marine Photobank
·       Photo of coral with black band disease courtesy of Sven Zea, Universidad Nacional de Colombia/Marine Photobank
·       Blast-fishing photo courtesy of Benjamin De Ridder/Marine Photobank
·       Photo of coral with yellow band disease courtesy of Craig Quirolo, Reef Relief/Marine Photobank
·       Before-and-after photos of bleached coral courtesy of Craig Quirolo, Reef Relief/Marine Photobank
·       Photo of bleached coral in the Galapagos Islands courtesy of David Jacobsen-Fried/Marine Photobank
·       Photo of dead coral reef in Taiwan courtesy of Konstantin Tkachenko/Marine Photobank
·       Bleached coral video footage courtesy of National Oceanic and Atmospheric Administration (NOAA)
·       Thermometer and coral reef illustrations: Marc Lussier, STScI
Written by Vanessa Thomas
Designed by Marc Lussier 
Music courtesy of Associated Production Music

An animation of Earth in a star-filled sky. Text, at-a-GLANCE, Coral Reefs
The globe turns.
The Pacific Ocean. A red circle around Fanning Atoll, Line Islands, Kiribati.
In the midst of a vast ocean, ringed islands of coral, called atolls, enclose shallow lagoons.
Atolls act as natural markers, encircling the places where now submerged volcanic islands once stood.
Arrows point to a Barrier Reef, an Atoll and a Fringing Reef. Society Islands of French Polynesia.
An atoll begins forming on the submerged rock just off the shores of an island, creating a fringing reef that traces the island's outline.
As the volcano subsides and the island erodes, the lagoon widens, transforming the reef into a barrier reef.
With continued subsidence and erosion, the island eventually disappears under water, leaving a ring of coral reef known as an atoll.
The whole process can take millions of years.