Geoparque Mundial UNESCO
Geoparque Villuercas > Nº02 – Cerro de San Cristóbal
The so-called Cerro or Sierra de San Cristóbal is an isolated mountain (hill) with a maximum altitude of 680 m, and some 2500 m in length, located to the south-west of the Logrosán village centre. This granite dome stands out some 200 m above the level of the surrounding peneplain.
It can be easily accessed by a wide path that starts at the Virgen del Consuelo hermitage, on the southern slope of the hill, and goes down a steeper path on the north-western slope.
During the visit, it is important to observe the granitic and subvolcanic rocks of the Sierra de San Cristóbal and its marked relief, which is the result of the resistance to erosion of these hard rocks.
We should pay attention to the remains of the mining site where the finest cassiterite crystals in Europe have been found.
The cassiterite (tin oxide; SnO2) crystals of this deposit were mined from the most remote antiquity until very recent times. Trenches, galleries and mining tools from the late Bronze Age related to the mythical kingdom of Tartessos (7th century BC) have been found at the top of the hill.
The view from the top, towards the north, faces a huge, sloping wall made up of a mountain range that runs from Zorita to Cañamero. What we see just in front of us is the Sierra de los Poyales y de las Paredes. In reality, these sierras make up the upper or raised block, with respect to the lower or sunken block of the penillanura, the result of movement through a great reverse fault produced by the last tectonic manifestations of the Alpine orogeny. The upper block is the so-called Garciáz raised block and the lower block forms part of the Guadiana depression.
If we look at the landscape to the east, we can see Cañamero, the Risco Gordo and the Sierra del Pimpollar and to the southeast the Cañamero and Logrosán rañas (see the brochures on these two geosites).
San Cristóbal Hill is composed of a granitic pluton from the Variscan Orogeny. It rises dome-shaped (approximately 200 meters above the Ediacaran peneplain, which is composed of greywackes, shales, and conglomerates), due to intense differential erosion, highlighting its geomorphological significance.
Associated with this granite, they are some series of mineral deposits with a history of mining dating from the Bronze Age to recent times. They preserve a heritage that, together with scientific dissemination, reinforces the educational value of this site.
RELIEF
From the summit of San Cristóbal Hill, several important geomorphological units can be distinguished in the landscape, depending on the direction of observation.
Panoramic view to the north (orange band)
To the north, the Sierra de Guadalupe can be seen, known in geology as the Garciaz block, which represents the division of the basement and the uplift of the block located to the north above the Ediacaran peneplain. This process took place during the later stages of the Alpine Orogeny.
Panoramic view towards the northeast (green band)
In this direction, the impressive Appalachian relief is visible, marked by the ridges of Paleozoic quartzite rocks, with their characteristic NW-SE orientation.
Panoramic view towards the southeast (yellow band)
On the horizon, a geomorphology of extensive platforms or plateaus separated by erosional channels, known as Rañas, can be observed. These were formed by the accumulation of relatively recent sediments from the Appalachian relief located to the north.
Panoramic view towards the south (blue band)
To the south, a relief that gradually softens until it becomes horizontal can be seen, formed by the Cenozoic and Quaternary sediments that fill the Guadiana basin.
