FALAISES
Falaises are a side continuously submitted by the sea' s action and they form the morphological elements typical of the rocky coats in erosion; they are destruction' s natural forms whose rests, removed by waves, supply the sandstones that then pile up on the beaches.
Falaises are formed by different parts. The BASE is the contact of a Falaise with the base level, where the sand piles up; the CREST is the higher point where the alteration is particularly fast; then there is a LEVEL SURFACE which goes on towards the interior; it is called FACE the Falaise inclined surface exposed to the sea, its inclination arrives to high values, near to 90° in the Falaises formed by the most resistant rocks, such as limestones, and assumes lower values, about 60-35à in those formed by less consolidated rocks as clayey sandstones; at last there is a zone called CONE, where there is some loose material of variable dimensions, piled up at the base and formed by the deposit of rocky rest.
Falaises are in permanent evolution, from this follows a general moving back of the littoral, this erosional process implies a constant land lose, at a rate that goes from 2mm to 2mt a year. The most beautiful places in the Algarve are these areas with an irregular erosion, between these two examples are Ponta da Pietade and the gulf of Vale do Lobo; but the natural beauty of these littorals is joined, for the visitors, to the constant danger of the Falaises' instability.
The urbanisation in the areas near the falaises, a wrong planning of the littoral occupancy and a growing use of these areas for many activities often help to increase the falaises' instability.
A falaise is, by definition, a geomorphologic element on recession, it's however a natural property to be safeguarded with the maintenance of its natural evolution, the erosion.
Falaises' evolution, the erosion.
Falaises' evolution proceeds through very fast movements of the mass, concentrated especially in winter when the main erosion agents (waves and precipitation) are more intense. Falaises' movement of mass are various in space and time, because they depends by many factors, such as the intensity and frequency of the atmospheric agents' action, the fracture and the kind of the rock, human occupation, the pesence of vegetation, the presence of seismicity, etc…
Erosion: in the falaises made by not much consolidated rocks the feature of having surface without support helps the formation of cracks parallel to the crest, that, by the outside agents, became deeper until they arrive to the breaking. In the higher places there is a mass movement and a consequent accumulation of the rest at the base. In the more consolidated rocks the mechanical action of the waves with the abrasive effect of the suspended sediments supply the consumption of the falaise's base and the consequent formation of the so-called "hoes". After some time these cavities became deeper and deeper, until they break, when in happens, there is the fall of the whole block, which has been undermined. The cone formed as a consequence of the mass movement supplies a temporary protection for the base, that, in this way, isn't subject to the waves' action.