Cave Research Group publication 14
1961 Oxford University Expedition to Northern Spain
|1961 Expedition Report (CRG 14)|
It is an advantage if the expedition geomorphologist is experienced and is also a photographer and fairly competent m line sketching, so that he may adequately record the features of the region to be studied.
The western massif of the Picos de Europa proved to be an excellent area for the investigation of limestone geomorphology, both on and below the surface. Many details of the rock forms were described and photographed, and a weather record was kept daily in order to define the summer climate of the area. The meteorological observations taken comprised rainfall, wind speed and direction, cloud amount and types, air temperature, rock temperature, relative humidity, barometric pressure, and prevailing weather conditions. The drainage of the area, and the survey of caves are described elsewhere in this report.
The area chosen consists of Mountain Limestone of Lower Carboniferous age, forming the northern limb of a major syncline, and surrounded by softer impervious slates and sandstone. The whole is an uplifted horst block, where the effects of glaciation and glaciofluvial action have combined to make a region of very steep slopes. There are several peaks over 2000 metres in height, the highest being Pena Santa 2596 metres above sea level. The rivers Cares and Dobra, the former separating the western and central massifs, flow in very deep valleys, excavated by glaciers and by glacial melt-waters. The steep slopes of the valleys contrast strongly with the more gentle slopes of the area to the northwest of Pena Santa, which may be related to an ancient erosion surface.
The presence of limestone has brought about a modification of the glacial topography, especially on this erosion surface, and although a few streams still flow on the surface, many of the valleys are dry. Of special interest are the 'hoyos' and 'jous', words used in the region to denote solution hollows, and outstanding among these are the Vega de Comeya, a flat-floored polje 2 km by 1 km, the Hoyo las Merinas and the Hoyo de las Pozas. The water from the Vega de Comeya may drain to the Rio Arganeo to the north and the Rio Pelarda to the southwest, but despite water tests using large amounts of Rhodamine B this has not been proved, and awaits further research. The strong relief, coupled with the quite heavy rainfall of the region, is favourable for the development of large cave systems. The expedition did not find potholes and caves deeper than 100 metres or longer than 1 km, but there is excellent scope for further discoveries.
Erosion levels on the surface are important in the investigation of cave formation. These were carefully recorded, together with the number of dolines occurring at different altitudes and on slopes of differing aspects, with a view to the investigation of the effect of altitude and aspect on the solution of limestone, and in particular of the influence, if any, of the climatic divide between the coastal region north of the Picos de Europa and the much drier interior.
Several rock surfaces, at altitudes ranging from 1000 to 2500 metres were studied for the development of runnels, furrows formed by trickling rainwater. Two types, a deep runnel on the semi-horizontal surfaces, and a shallow runnel on vertical surfaces, were found to be widespread up to about 2300 metres, above which frost shattering obliterated both forms.
Rock forms should be studied in the context of the climatic conditions. The meteorological observations taken are given in Table 2.
W.J. Crompton, Lincoln, February 1964.