In the Belly of Barbados
Anjani Ganase, marine scientist, explores Barbados, which is geologically different from Tobago; and ventures into two cave systems, one formed by fresh water, the other by the ocean.
Barbados, unlike Trinidad and Tobago, is the iconic Caribbean island; white sandy beaches, electric blue water and bright sunshine. Visitors flock to the beaches and go on seaside adventures - snorkelling, diving, skiing and surfing. However, Barbados also has treasures for those who trek inland or below. Beneath the surface of Barbados there is a trove of caves, karsts and many other impressive rock formations, from its unique geological history. Barbados is not actually part of the Lesser Antilles (it is located directly east of St. Vincent) along the edge of the Caribbean tectonic plate; and the history of islands born out of volcanic eruption does not apply to Barbados. Instead, Barbados sits on the Atlantic tectonic plate, which pushes below the Caribbean plate. Barbados is connected to a larger submerged ridge that was formed from collected sediment at the edge of the Atlantic plate as a result of the two plates grinding against each other. In the shallow portions of the ridge, coral reefs formed and grew over the sediment and over time created the foundation of Barbados as a coral island (made up of limestone).
While the form of the coral rock – still reflective of ancient reefs - is quite unique, other elements, such as the rain, streams and the ocean sculpt Barbados’ infrastructure. Historically, the many caves on the island served many purposes. Some caves were used as hideouts for escaped slaves, while others were used to imprison slaves. Even today caves are still used as hideouts or meeting places for romantic dates. Some of the larger caves are now popular tourist attractions. The two most popular cave systems - Harrison’s caves and Animal Flower cave – were created from different processes of erosion.
|Formation of stalactites (above) and stalagmites (below) in Harrison’s Cave. Photo by Anjani Ganase|
Harrison’s cave is located in the centre of Barbados near the oldest part of the island. Discovered by the landowner Thomas Harrison in the 1700s, it was only fully explored and mapped during the 1970s by two Barbadians - Tony Mason and Allison Thornhill - and Danish engineer, Ole Sorenson. The cave system is located about 200 m above sea level but extends about 2 km in length and is about 69 m deep (Kambesis and Machel 2013). Harrison’s cave was formed from fresh water seeping underground; over time, as the water dissolves the limestone, the cracks turn into tunnels and caves. In these spaces the most majestic sculpted forms are created: stalactites and stalgmites. Dissolved limestone (calcium carbonate) left behind as the water drips off the roof of the caves creates stalactites. The limestone that pools on the bottom collects and rises into other pillars. These are stalagmites, rising from the floor of the cave. Over time, in the absence of any disturbances, the downward stalactites may meet and fuse with the stalagmites. Imagine being the first to view these spectacles, crawling and climbing along the escarpment of the cave in the dark with only a torch to light the way. Today visitors get a different experience. On the guided tour, trams carry spectators down narrow paths through well-lit archways into large ballrooms filled with chandelier like stalactites hanging from the ceiling and stalagmites rising up to meet them.
|Underground waterfall and pool in Harrison’s Cave. Photo by Anjani Ganase|
On the other hand, the Animal Flower cave located in the northern cliffs of Barbados is a sea cave. As it is not connected to any streams, the constant pounding of the ocean waves - along with natural shifts in the rock structure, and the changes in sea level - is likely responsible for the shape of this cave (Kambesis and Machel 2013). You descend into the cave by ladder. From the top of the cliffs going down, you can view the layers of coral piled on top of each other as if you are descending through time; some more distinguishable branching and plating coral forms are clearly visible. The mouth of the cave faces seaward, eye level to the wild Atlantic Ocean and on a more turbulent day, the cave would be submerged. The power of these ocean waves has strewn large boulders across the cave floor. The internal structure of the cave isn’t smooth but consists of a series of pools, some big enough to swim and wholly submerge yourself in. The “animal flowers” that give the cave its name are actually feather duster tubeworms that inhabit the pools which are flooded by crashing waves, and which feed on the stirred up particulates. Once abundant, these tubeworms are now scarce, perhaps the pools have naturally become less habitable or perhaps the persistent touching of visitors who want to see them retract into the tube may have stressed them out.
|Ocean view from Animal Flower Cave. Photo by Anjani Ganase|
Barbados is also riddled with sinkholes (Kambesis and Machel 2013). These are less obvious geological structures; but sudden changes in the infrastructure from vibrations or earthquakes may result in the collapsing of these sinkholes to create gullies (Kambesis and Machel 2013). The exploration of the geological structure is not only important to understanding the island’s history but to also assess the safety of future infrastructure.
Kambesis, P. N. and Machel, H. G. (2013). Caves and Karst of Barbados, Chapter 10, Coastal Karst Landforms, Coastal Research Library 5, by M.J. Lace and J.E. Mylroie (eds.),
Springer Science and Business Media, Dordrecht