Tenerife’s waters are home to a spectacular array of marine life.
Capture it on camera with World Press Photo award winner.
The formation in the picture is an example of columnar jointing, which occurs in a variety of geological environments. In this case it was created by a basalt lava flow. As it cooled down the lava solidified and contracted, and in contracting it fractured. The fractures began at the surface of the lava, on the top, the sides and the base. From there they worked their way into the interior, following the path taken by the cooling process. Typically when this happens the surface fractures are irregular, but as they penetrate the interior they organise themselves into 3 – 7 sided prisms, mostly in the form of 6 sided hexagons. For this reason columnar jointing is also known as hexagonal jointing.
Usually we see two zones that display different shapes and sizes. There’s an upper entablature of thinner, irregularly shaped and curving columns, and a lower colonnade of wider, vertical columns, sometimes with an undulating surface. An entablature results from fractures descending from the upper side of the lava flow, and a colonnade from fractures rising from the base.
Above the entablature you will see a fragmented zone which was formed by erosion. This suggests that some time after the lava solidified beneath the water, the sea level fell and exposed it to the elements, probably during a period of glaciation. The flow itself happened between half a million and a million years ago.
The most famous example of columnar jointing is the Giant’s Causeway on the coast of Antrim in Northern Ireland. The USA has the Devil’s Postpile in the state of California.
In Tenerife there is to our knowledge only one quite small example of an exposed formation that was previously submerged. It’s in Los Realejos at the Playa de los Terreros, and it’s significantly smaller than the underwater formation that we will visit.