Surrounded by darker, deeper ocean waters, coral atolls often glow in vibrant hues of turquoise, teal, peacock blue, or aquamarine. Belize’s Lighthouse Reef Atoll fits this description, with its shallow waters covering light-colored coral: the combination of water and pale corals creates varying shades of blue-green.
Within this small sea of light colors, however, lies a giant circle of deep blue. Roughly 300 meters (1,000 feet) across and 125 meters (400 feet) deep, the feature is known as the Great Blue Hole.
The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite captured this image of the Great Blue Hole and Lighthouse Reef in the Caribbean Sea on March 24, 2009. The Great Blue Hole appears at the center of the image, surrounded by a ring of lighter color caused by elevated coral. In fact, parts of the ring surrounding this feature actually crest the water surface at low tide, but a layer of shallow water covers most of Lighthouse Reef Atoll.