The Lighthouse Atoll in the Belize Barrier Reef is featured in this image acquired on 29 March 2011 by Japan’s ALOS satellite. In the upper-central part of the image, an underwater sinkhole known as the Great Blue Hole appears as a dark blue circle. Surrounded by the shallow waters of the coral reef, the Great Blue Hole measures over 300 m in diameter and about 123 m deep. Formed when the sea level was much lower, rain and chemical weathering eroded the exposed terrain. Water later filled the hole and covered the area when the sea level rose at the end of the ice age.
Also visible in the image are two coral islands – green with vegetation – called cayes. The larger to the west is Long Caye, and the smaller Half Moon Caye is to the east.
This image is featured on the Earth from Space video programme.