The Great Blue Hole
From the air, the Great Blue Hole of Belize resembles an otherworldly
maw, intent on drinking down the surrounding Lighthouse Reef Atoll. In
reality, the 1,000-foot (305-meter) wide hole is simply a sinkhole in
the ocean. Geologists believe that an underlying cave system collapsed
under increased pressure some 10,000 years ago due to rising sea levels.
The dark hole descends 412 feet (126
meters),
terminating in lightless depths where a lack of oxygen prevents most forms of life from thriving. Divers rarely plunge these depths, however, as most are content to explore the stalactite-rich caverns accessible from depths of some 130 feet (40 meters) below the surface.
terminating in lightless depths where a lack of oxygen prevents most forms of life from thriving. Divers rarely plunge these depths, however, as most are content to explore the stalactite-rich caverns accessible from depths of some 130 feet (40 meters) below the surface.
From hidden depths to towering
vistas, these are just 10 of Earth's countless geologic wonders -- each
more than a rival for anything dreamed up for fiction and fantasy. We
live on a spectacular planet; you just have to open your eyes to it.
Explore the links on the next page to learn even more about Earth's amazing geology.
Subterranean Splendor
The hill country of Kentucky's Green
River Valley certainly has its charms, but beneath its gentle woodlands
there is an underworld. More than 390 miles (628 kilometers) worth of
caves worm through the rocky depths, making Mammoth Cave the largest known cave system in the world.
For more than 10 million years,
waters from the Green River have cut through the soft limestone,
riddling it with all manner of cave formations. A visitor may pass
through a lengthy passageway and
into a vast cathedral. Vertical shafts descend into darkness while stalagmites, stalactites and bizarre crystal formations speak to the immensity of geologic time.
into a vast cathedral. Vertical shafts descend into darkness while stalagmites, stalactites and bizarre crystal formations speak to the immensity of geologic time.