Karstic relief is a type ofrelief which develops inrocks that are soluble inwater, mainly limestone,although karsts ingypsum are alsofrequent, like thosefound in the SorbasDesert (Almería).
For a good karstic relief to develop onerequires a humid climate, sufficient time, asufficiently thick calcareous mass and ahorizontal orientation of the limestone layers.
Although limestone is impermeable, it has a secundary permeability dueto it being very fractured and having a great number of joints. Thisallows rainwater to easily filter in and slowly dissolve the interior.
Limestone is formed from calciumcarbonate, insoluble in pure water,however, when it rains therainwater reacts with the carbondioxide in the atmosphere formingcarbonic acid. This is a weak acidwhich reacts with the calciumcarbonate transforming it intosoluble calcium bicarbonate whichis then washed away by water. Inthis way, limestone is dissolvedaccording to the followingreaction: Dissolving of limestone → Ca C O 3 + H 2 O + C O 2 ⇄ Ca C O3+ H 2 C O 3 ⇄ Ca (H C O 3) 2 ← Formation of stalactites and stalagmites
These processes create a relief with characteristic shapes on surfaces(exokarstic shapes) and interiors (endokarstic shapes).
EXOKARSTIC SHAPESLapiesDolinesUvalasPoljes or karstic plainsSinkholes (ponors)Corridors or alleys (callejones)Upwellings or springs
LAPIESA group of small canals or narrow furrows separated by sharp crests.They normally occur on surfaces more or less inclined and absent ofvegetation.It is an uneven terrain with difficult access. In the Torcal many of theseareas are called “agrios”.
DOLINESThese are circular orelliptical depressionsformed by dissolving atthe point where twocracks cross, or by thecollapse of the ceiling of acavern. In this last casethey appear surroundedby vertical walls calledTORCAS which areabundant in the Torcal ofAntequera, giving rise toits name. Normally thebottom is filled with"terra rossa" ordecalcification clays.
UVALASAs a consequence of the evolution of the doline, faster on the surfacethan depth, uvalas are created by the union of proximate dolines. Theirdimensions can reach up to 1km in diameter.The union of two proximate dolines gives rise to 8-shaped uvalas. W IDE ALLEY
LLANOS DE LÍBAR LPOLJES OR KARSTIC PLAINS These are the largest and most evolved superficial shapes. They are flatbottomed depressions and normally occur in an elongated shape (length ismore than double the width) and are conditioned by important fractures.From 2km and up it is considered a “polje” and not an “uvala”. These areascan be dry or seasonally flooded, streams and even rivers can flow throughthem, which normally end up going down sinkholes or “ponors”.
DARK ALLEYCORRIDORS(ALLEYS)These are more orless narrowpassages in themiddle of thelimestone formedby the dissolving ofthe vertical wallsof the crack.
SIMAS These are verticalcavities, formed either byvertical fractures wheredissolving and erosion havereached great depthsanywhere up to 1000m, orby the collapse of a doline.
CAVE IN THE “NACIMIENTO DE LA VILLA”CAVES, CAVERNS ANDGALLERIESThese are hollow areas in the interiorof limestone which are formed whenwater dissolves horizontal cracks.
CAVE IN THE “NACIMIENTO DE LA VILLA”Water drips from theceiling of caves via holes orcracks, around whichcalcium carbonate isdeposited. With time thesedeposits grow downwardforming stalactites.
CAVE IN THE “NACIMIENTO DE LA VILLA”The water which falls to the floor also leaves calcium carbonatecausing stalagmites to grow upward. A column is formed when theymeet. When water drips through a crack, sheets of calcium carbonatecalled elephant ears may grow downward.