Rock on, Alicante!
The Canelobre Caves
Last month I mentioned the Jurassic limestones and explained how they were deposited in a
shallow marine tropical environment. These limestones can now be found forming the mountain
range in Busot, known as the Serra del Cabeço d’Or, as they have been exhumed and folded by
the collision of the African continental plate and the Eurasian continental plate. These two chunks
of the earth crashed into each other and raised and deformed everything in between.
In these limestones there are a lot of caves - the Canelobre caves in Busot being the most well
known and a very popular tourist attraction. Lately I have heard a lot of people talking about them
and saying lots of crazy things, such as the mountain being a volcano and the caves a bubble in
the lava, so I thought I should clear things up for you all.
So let’s do a bit of chemistry to start off this article and explain how the caves were formed.
The following equation is basically a very simplified summary of how a cave in a limestone is
formed (without taking into account lots of other factors such as temperature and PH):
CaCO3 + CO2 + H20 → Ca2+ + 2HCO3Now don’t get freaked out by all these chemical symbols and numbers! It’s really quite simple to
understand. Now the first term is the calcium carbonate (CaCO3), also called calcite, which is the
main component of the limestones in which the caves are formed. When it rains the water (the
H2O) collects carbon dioxide (the CO2) from the air and the soil as it filters through it. This makes
the water slightly acidic (turning it into carbonic acid or H2CO3) which “eats” away at the limestone
by dissolving the calcite. The result is a water with dissolved calcite, which is generally a calcium
bicarbonate solution (just another fancy name for water with calcite in it), which has left behind a
cavity (the cave) where the calcite originally was. When this water finds a surface, such as a cave
wall or roof, the reaction is reversed when this water with the dissolved calcite comes into contact
with the air and is degasified. The water drips and leaves behind the dissolved calcite which
accumulates and forms all sorts of interesting speleothems (the fancy name for stalactites and
stalagmites and all those sorts of things).
Remember which are which? The stalactites are the ones that grow down from the ceiling and
have a hollow centre which the water travels down through, when the water drips off the end the
calcite precipitates around the hollow tube. The stalagmites are the ones that grow up from the
ground and don’t have a hollow centre as the water doesn’t travel through them but falls from
above, splashes, and leaves some calcite behind. When the two meet you get a column. Another
type are flowstones which form in a similar way, but when the water flows over the surface instead
of dripping off of it, and create curtain-like features.
So a quick summary on the geological formation of the caves: the Jurassic limestone layers were
folded by the alpine orogeny (the collision of the two previously mentioned plates which created all
the major mountain ranges around the Mediterranean) creating a “n” shaped fold, with the western
side’s layers almost vertical and the eastern side’s layers less vertical. All this was fractured as well
giving a kind of 3D criss-cross of weaknesses in the rock. Then, over hundreds of thousand