Bermuda is a natural haven for geologists and non-geologists alike, from the black volcanic rocks that punctuate the shoreline to the pink sand and boiler reefs at the surface of clear turquoise waters. In this series The Bermudian will investigate the best places to see Bermuda’s geology.
The Crystal Caves were discovered in 1907 by two boys playing cricket. Their ball went missing down a crevice in the ground. Upon further examination, they found the hole opened into an enormous underground cavern, complete with intricate geological formations and deep pools of crystal clear water. Today the Crystal Caves are available for paid walking tours for anyone willing to descend the 81 steps into the earth. The trek downward is rewarded by an underground wonderland of geological marvels.
Speleothems, sometimes referred to as formations or decorations, are cave features formed by the deposition of minerals. The speleothems with which most people are familiar are stalactites and stalagmites. Stalactites grow down from the cave ceiling, while stalagmites grow up from the cave floor. It’s easy to remember which is which: Stalactites have a “T” for top and stalagmites have a “G” for ground. You’ll find both in Crystal Caves.
The formation of stalactites is caused by the slow percolating through the rocks of water containing minerals which it has gathered on its way through the earth. In all limestone caves stalactites form in great abundance as glittering white columns covered with a thin film of water. As the water, dripping from the roof of the cave, becomes exposed to the air, some of it evaporates, leaving the remainder so supersaturated that a deposit of lime is left, and with the passage of years and the steady dripping of water from the same spot a column of white calcite is formed.
For the perfect development of these stalactites, certain conditions are essential. The trickle of the water must be very slow, and the rate of evaporation regular. Currents of air would destroy the formation. Changes of temperature will interfere with the evaporation, sometimes accelerating and sometimes slowing it, and under these conditions the stalactites tend to stop growth or to become incrusted with irregularities and excrescences.
In the Crystal Cave the conditions are ideal; the air is perfectly still and consequently perfect stalactites have formed in profusion. By carefully measuring the rate of growth of these crystal-like formations it has been estimated that some of the larger stalactites have taken from a hundred thousand to two hundred thousand years to form.
In one of the Moravian caves a stalactite about as thick as a penholder was broken across in 1880, and a decade later it had grown in length nearly an inch. From calculations based on this it was judged that such a stalactite, seven feet long, may have been formed in four thousand years. This gives a sense of how ancient the Crystal Caves must be.
Geologist or not, the otherworldly experience of exploring these spectacular caves and their ancient formations will certainly leave a lasting impression.
