The Great Blue Hole, a submarine sinkhole off the coast of mainland Belize, yawns wide in an image captured by GeoEye's Ikonos satellite on Dec. 8.
The Great Blue Hole is one of the natural wonders of the world, lying off the coast of Belize in the midst of the Lighthouse Reef Atoll. It's a circular sinkhole measuring about 1,000 feet (300 meters) wide and more than 400 feet (124 meters) deep. It was apparently formed as part of a cave system tens of thousands of years ago, when sea levels were much lower. When the ocean's waters rose, the caves were flooded. The Great Blue Hole is part of the Belize Barrier Reef Reserve System, which UNESCO has designated a World Heritage Site.
Archaeologists and historians say the reef system provided fishing grounds for Maya communities more than a millennium ago, and later served as a haven for 17th-century pirates and buccaneers. Today, the reef is a haven for scuba divers and for marine species at risk, including West Indian manatees and green turtles.
This picture of the sinkhole and its surroundings was captured by GeoEye's Ikonos satellite on Dec. 8, from an altitude of 423 miles (681 kilometers). It serves as today's offering from the Cosmic Log Space Advent Calendar, which features outer-space images of Earth every day from now until Christmas. Sample these other goodies from the calendar:
- 2012 Cosmic Log Space Advent Calendar
- Day 1: A fantastic Chinese fan
- Day 2: Satellite shows a Grander Canyon
- Day 3: Typhoon stirs awe — and alarm
- Day 4: Glittering nighttime view of Riyadh
- Day 5: Night lights shine on 'Black Marble'
- Day 6: Holy sites seen at night
- Day 7: Blue Marble still leaves its mark
- Day 8: Satellites look into a volcano's hell
- Day 9: Jack Frost nipping at Alaska's nose
- Day 10: Cosmonaut looks down on peaks
- Day 11: Earth looms above moonwalker
- Day 12: Skytree casts shadow on Tokyo
- Day 13: Aurora sets stage for meteor show
- Day 14: Apollo's last look at Earthrise
- Day 15: A sobering moment from space
- Day 16: Middle Earth spotted from orbit
- Day 17: Mount Etna erupts ... in 3-D!
- 2011 Cosmic Log Space Advent Calendar
- 2010 Cosmic Log Space Advent Calendar
- The Atlantic: Hubble Advent Calendar
- Zooniverse Advent Calendar
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other science and space news coverage, sign up for the Tech & Science newsletter, delivered via email. You can also check out "The Case for Pluto," my book about dwarf planets and the search for new worlds.