GEOLOGY OF THE AREA
Physical geography and geology of Spain
There is no point in us re-inventing the wheel - See the excellent Iberia Nature website for a general description. The same website also gives an interesting account of earthquakes in Spain
The landscape in the Marina Alta is described as being "karst"
- typical of limestone areas eroded by water. About half the the land of Valencia
has this type of landscape. For example, the numerous dolinas (basins)
scattered over different districts such as around The Monduver Massif (la Safor
District) with over 250 dolinas. Some rivers flow through narrow defiles created
by karstic processes: The Montileó,
the Mijares, the Turía and the Júcar. A spectacular example
in the Marina Alta is the Barranco del Infierno (Hell's ravine)
near Vall De Ebo
There is also a sizeable number of subterranean formations in the land of Valencia. An inventory of over 6000 caves has been drawn up, all of which are protected under the Law covering natural areas in view of their unique geomorpholical and biotic value. Today, the formation of caves and karst landscapes is barely active.
The majority of the karst features in the region have been inherited from former climatic periods. The land of Valencia is thought to have undergone an intense karstic formation during the Pliocene (end of the Tertiary), between two and 5 million years ago), just before the climatic crisis of the Quaternary that resulted in the present day climate. Five caves have so far been prepared for tourists visits in the land of Valencia : Les Coves de San Josep (La Vall d'Uixó) Cueva de Don Juan (Jalance), Cove del Rull (Vallde Ebo), Cova de les Calaveres (Benidoleig) and les coves del Canelobre (Busot).
Key: (diagram from Cova del Rull, Vall D'Ebo)
2. Ruin-like relief
3. Rock Shelter
7. Fossilised emergence
Karst landscapes are usually impressive because of the variety of spectacular and unusual formations they contain. Such formations are created due to the greater solubility of certain rocks by natural water. Not all rocks are easily soluble by any means, but this is the case of carbonated rocks such as limestone, dolomite, and some others such as gypsum. The main role contained in carbolic carbonated rocks, calcite, is not directly soluble in water; it requires the presence of carbolic acid formal calcium bicarbonate which is soluble. The quantity of carbolic acid, ambient temperatures, precipitation levels and atmospheric pressure are other important factors in determining the possibility and the intensity of karst development, which combined with other erosive of agents, is capable of creating authentic sculptural and relief work and highly attractive landscapes. In the tropics, karst landscapes are sometimes enormous in size and breathtakingly beautiful. In the Mediterranean area of Spain, karst development is more discreet, appropriately in harmony with human scale of local landscapes.
Karst terrain displays both external forms such as lapies, dolinas, gorges and ravines, natural bridges, rock shelters, pepino hills, etc and internal forms like caverns and sink holes. All of these formations are due to the continued presence of water. Changes in climatic conditions and the absence of water may arrest karst development, thus forming what may be called fossilised caves in which mineral dissolution is barely operative. This produces what are known as clastic processes whereby blocks and pieces begin to fall off, complemented by the deposition of sediments as dissolved calcium carbonate begins to precipitate. This gives rise to reconstructive process during which is sizeable number of concretions are produced, taking on highly varied forms and sizes and converting such caves into spaces where fantasy reigns, with a profusion of stalactites, stalagmites, curtains, columns, flowstone, gours, etc representing the geological work of centuries, but often appearing to the human eye as the creative work of nature.
In addition to rock, karst domains contain other features living on a different
timescale in the form of flora and fauna adapted to subterranean ambient conditions.
In specialist language: troglodite fauna (exclusive cave dwellers), troglophile
fauna (frequent cave dwellers) and trogloxene fauna (occasional cave dwellers).
But in general a cave is a domain in which evolution is marked by the slow
dripping of water. Landscapes and life are enclosed within the dark walls of
underground passageways that we can now visit as tourists thanks to the facilities
provided in many caves in the region.
(Text adapted from notice outside Cova del Rull; Vall D'Ebo)
Marina Alta Walks