Out on the remote cayes of Lighthouse Reef Atoll, ecosystems both above and below sea level have remained largely unchanged for hundreds of years. And the main attraction for scuba divers is a veritable geological wonder: the famous Great Blue Hole.
From above, this renowned dive spot looks like a dark blue circle in the middle of a vast expanse of turquoise. An aerial view awakens you to an oft-forgotten aspect of the ocean: its mind-boggling depth. The most frequently quoted ocean statistic is the fact that water covers 75% of Earth’s surface. Impressive, yes, but this stat nonetheless discounts the depth. Gazing down at the Great Blue Hole, it hits you. This blue-black void plunges into the heart of the ocean.
Divers seek this limestone sinkhole for a challenge and a thrill, but also for an education in natural history. The Great Blue Hole’s geological past spans 150,000 years, back to a time when it actually existed above ground, as evinced by the presence of stalactites in its underwater caves. Although many mysteries remain as to the origins of the Great Blue Hole, scientists believe that a series of dry caves predating the Ice Age gave rise to the submerged sinkhole of today. Sometime before the last great thaw, an earthquake shook the area to an angle of 12 degrees, which explains why the stalactites hang so strangely tilted.
Following this seismic upset, the melting of the last Ice Age flooded the cave systems and eventually the limestone ceilings of the once-dry caves collapsed under the weight of the water, creating one giant sinkhole 1,000 feet in diameter and over 400 feet deep. It’s a true geological oddity, appearing in stark contrast to the surrounding waters, which are so shallow that the coral peeks out of the sea at low tide.
Underwater explorers who are not yet ready to attempt the Great Blue Hole often visit the coral that circumscribes it for some of the world’s best snorkeling and diving. A plethora of plants and animals inhabit the reef; lobsters, turtles, and schools of bright fish swim and feed in patches of the purple coral found around the Great Blue Hole, while the hole itself harbors virtually no marine life. Occasionally, a Caribbean reef shark or barracuda will pass through its upper regions, but the best sights within the Great Blue Hole are architectural. The magnificent structure of this underwater cave evokes an hourglass. A sheer limestone wall drops 50 feet to an overhang that supports enormous stalactite rock formations, then down to depths even expert divers cannot safely reach.
Local myths maintain that the Great Blue Hole is bottomless, while other legends claim it holds terrifying sea monsters. These likely originated with the ancient Maya, who viewed sinkholes as sacred entryways to the underworld. In 1972, Jacques Cousteau descended to the very bottom in his research vessel, The Calypso, shedding light and fame on the deepest mysteries of the Great Blue Hole. He declared it one of the top ten scuba diving sites in the world. There have been rumors that Cousteau used dynamite to blast through part of the coral around the Great Blue Hole in order to navigate his boat, but these are fairly unsubstantiated, although Cousteau has admitted to employing explosives in other areas of Belize.
In the years following Cousteau’s exploration, the Belizean government established the site as a National Monument and UNESCO designated it a World Heritage Site, ensuring its preservation for generations to come. Dive trips to the Great Blue Hole are usually day-long events, and often include dives in the nearby reef and a visit to the idyllic, isolated Half-Moon Caye. The eco-resort on Zophora promises to all but eliminate travel time to the Great Blue Hole while accommodating adventurous divers in sustainable luxury on Long Caye, located just 15 minutes from this geological wonder.
Tuesday, August 06, 2013
Geological History in the Depths of Belize’s Great Blue Hole