The Hospital del Obispo site is a “nava”: an elevated or “hanging” valley above the other valleys in the area, situated at an altitude of about 1,000 m. It is located in the westernmost part of the municipality of Villar del Pedroso, on impermeable shales of the Ibor Group (which include numerous fossils of vendotaenids and sabelliditids in this area). The Armorican Quartzite lies discordant on them, forming the pronounced elevations of the Sierras del Rullo and Hospital (Cerro Fortificado – fortified hill) which are located between the villages of Navalvillar de Ibor and Navatrasierra. As in Geosites 11 and 41, in the contact between the Armorican Quartzite and the impermeable Ediacaran materials, important aquifers emerge, as is the case of the Fuente del Hospital del Obispo, which discharges its waters into the gorge, where peat bogs develop.
The Hospital de Obispo nava (elevated plain) has a gentle longitudinal profile, with a lower topographic gradient than the other valleys drained by the streams in the area. Therefore, as drainage is so slow due to the low gradient, the waters from the aquifers puddle, soaking the clay and silt sediments deposited there, giving rise to small pools known as ‘bohonales’, ‘tembladeros’ or ‘trampales’ where peat bogs develop.
Peat is an organic material, not very compact and rich in carbon and water. Its appearance is spongy and light, in which the remains of the plant materials (generally mosses) that gave rise to it can still be seen. The formation process consists of the accumulation and putrefaction of plant remains, generally mosses, in permanently waterlogged areas with anaerobic conditions (very low oxygen concentration). Peatlands are one of the poorest ecosystems in terms of nutrients, with a significant deficit of nitrates in the soil, due to the fact that the permanent waterlogging of peatlands acidifies the environment and does not allow the presence of bacteria and fungi, which nitrify the most fertile soils. Thus, the whole is mineralised with a high concentration of carbon. The peat in formation darkens as the mineralisation process progresses and the volume increases by a few millimetres per year. Peat bogs have preserved material for thousands of years and can be dated for age.
All this has given peat bogs an added interest, since they are home to a very peculiar and interesting vegetation that has developed different mechanisms to adapt to this shortage of nutrients and that in many cases constitutes botanical endemisms of great importance. The residual parts of the plants, instead of decomposing, accumulate over time under the new shoots of the moss and form peat.
The exotic character of these “trampales” of the Hospital del Obispo is provided by round-leaved sundew (Drosera rotundifolia), commonly known as “Rocío del Sol”, an insectivorous plant that makes up for the lack of nutrients in the soil with the ability to obtain food from the digestion of small insects that are trapped in the sticky secretions of the hairs of its leaves.
