Antonio Gómez Ortiz’s research while affiliated with University of Barcelona and other places

An accurate review of the literature on surface exposure dating methods shows evidence of the difficulty in applying cosmogenic dating methods to old moraines because of the intensity of late Quaternary erosion processes. Moreover, as in some previous cases, we also found special difficulties in applying these methods to LIA moraines, caused by the intensity of current paraglacial processes. The objective of this study is to apply cosmogenic dating methods to very old and very young moraines, which in both cases have been or are being affected intensively by erosion. With this purpose, we collected samples of boulders from moraines corresponding to (i) the penultimate glaciation and (ii) the Little Ice Age (LIA), both from Sierra Nevada in the south of the Iberian Peninsula. The sampling strategy was based on a preliminary accurate analysis of the geomorphological settings of two valley sites that resulted in the collection of only four boulder samples from an old moraine and three more from a very recent moraine. Using in situ-produced cosmogenic 10Be to date these boulders, the old samples yielded an age of ca. 130-135 ka for moraine stabilization. The younger samples indicate that the LIA moraine accretion probably occurred between the fourteenth and seventeenth centuries, with a subsequent stage of accumulation during the nineteenth century as suggested by historical documents. Dating a glaciation that occurred prior to the last Pleistocene glacial cycle and dating LIA glacial stages are novel in the context of Iberian glaciations and agree with other palaeoenvironmental studies in Iberian and in other European mountains. The limited number of boulders adequate for cosmic-ray exposure dating prevents statistical methods to be applied, and therefore highlights the need to improve geomorphological criteria in sample selection.

Sierra nevada es una montaña con identidad singular, particularmente por el valor patrimonial que suponen sus paisajes naturales y culturales. los primeros, refle-jados en su rica diversidad y los segundos, por la huella secular del hombre en el territorio. Estas circunstancias propician que pueda ser motivo de estudio destacado en los curricula de los niveles educativos, específicamente desde la Geografía. la atención que se preste a ellos, garantiza el desarrollo de conocimientos científicos, adquisición de competencias y creación de valores de alcance social, de tanto interés en la educación actual. Palabras clave didáctica, Geografía, Paisaje, Sierra nevada, Valores Patrimoniales. Abstract Sierra nevada is a singular mountain environment, particularly because of the natural heritage of its natural and cultural landscapes. The first are reflected in its rich diversity and the latter by the historical impact left by societies in the area. These circumstances suggest that its study should be included in the study plans, particularly from Geography. This would reinforce the development of scientific knowledge, acquisition of skills and creation of social values, of much interest in education today.

Abstract (The periglaciation of the Iberian Peninsula): Mountain environments in the Iberian Peninsula were heavily glaciated during the Last Glaciation. However, glaciers were mostly confined within the mountain valleys. Lower areas as well as the highest lands where topography did not favour ice accumulation were affected by intense periglacial processes. Since then, climate conditions have conditioned the spatial distribution of periglacial activity, moving uphill or downhill according to the intensity of the cold. Therefore, a wide range of landforms and deposits are distributed in Iberian mountains attributed to different past periods with changing climate conditions. These periglacial conditions are compared with current activity in the present-day periglacial belt in each of these mountain ranges.

Soil temperatures play a key role on the dynamics of geomorphological processes in periglacial environments. However, little is known about soil thermal dynamics in periglacial environments of semiarid mid-latitude mountains, where seasonal frost is dominant. From September 2006 to August 2012 we have monitored soil temperatures at different depths (2, 10, 20, 50 and 100 cm) in a solifluction landform located at 3005 m.a.s.l. in the summit area of the Sierra Nevada (South Spain). Mean annual temperatures in the first meter of the soil ranged from 3.6 to 3.9 °C while the mean annual air tem-perature at the nearby Veleta peak was 0.08 °C. Therefore, these data point out the inexistence of widespread permafrost conditions today in this massif. Seasonal frost controls the geomorphodynamics even in the highest lands. Climate conditions have shown a large interannual variability, as it is characteristic in a high mountainous Mediterranean environment. These variations are reflected in the patterns of soil thermal dynamics. The depth and duration of the frozen layer are strongly conditioned by the thickness of the snow cover. The date of the first significant snowfalls conditioned the beginning and rhythm of freezing of the soil. Wet years resulted in a thick snow cover which insulated the ground from external climate oscillations and favored a shallow frost layer (. On the other hand, years with low precipitations promoted deeper freezing of the soil down to 60–70 cm extending until late May or early June. When snow melted a high increase of temperatures of 10–12 °C in few weeks was recorded at all depths. At this time of the year, periglacial activity is enhanced due to higher water availability and the ex-istence of freeze–thaw cycles. These were recorded mostly in spring and autumn in the first 50 cm depth of the soil, ranging from 9.8 days (at 2 cm) to 3.7 days (at 50 cm). However, the inactivity of solifluction landforms suggests that the combination of present-day soil temperatures together with moisture conditions is not favorable to promote solifluction activity in the periglacial belt of the Sierra Nevada. Future climate scenarios point to a temperature increase and precipitation decrease in the area, which would entail deeper but shorter frozen soil layers. These conditions would not be favorable for active periglacial slope processes in the Sierra Nevada.

In the highest land of the Sierra Nevada National Park, an experiment to monitor solifluction rates together with the thermal regime of the ground was implemented during the period 2005–2011. Data show evidence of the low activity of solifluction processes in the present-day periglacial belt of Sierra Nevada. Annual displacement rates were lower than 1 cm yr–1 both in northern and southern slopes. Solifluction was more active near snow patches and streams. Rates were also higher during snowier years. Soil temperatures showed seasonal frost occurrence, though the depth and duration of the frozen layer is strongly conditioned by the annual snow cover. Water availability appears to be a crucial factor for solifluction processes in this semiarid environment.

Knowledge to the Quaternary environmental evolution in the mountains of the Iberian Peninsula has advanced substantially in recent decades. Particularly significant are the progress made in the Sierra Nevada massif, in the southern peninsular. In this case, researchers have used natural records and documentary sources to reconstruct the environmental dynamics from the last glaciation and subsequent deglaciation of the massif to their recent evolution. Detected environmental changes can induce climate variability during the past millennia. The impact of human activity on the peaks of the Sierra Nevada has been significant for the upper Holocene, particularly from the Muslim occupation.

Our knowledge of the Quaternary landscape evolution in the high mountain areas of the Iberian Peninsula has substantially improved over the last decades. The Sierra Nevada is one of the most studied mountain ranges in southern Europe regarding its environmental evolution. The purpose of the present paper is to integrate and summarize all the studies focused on the reconstruction of the palaeoenvironmental history in this massif since the Last Glaciation. Research has focused both on different sedimentary records and historical sources. A wide range of geomorphological, sedimentological and geochronological techniques have been used to characterize the glacial, periglacial, wetland and lacustrine records for palaeoenvironmental purposes. For the last nine centuries tens of descriptions, maps and sketches describe the landscape of the summit area of the Sierra Nevada, providing evidences of the historical environmental events. Based on a multi-proxy approach, five periods have been identified: Last Glaciation, deglaciation, Holocene, Little Ice Age and recent evolution. Recent studies have detected the maximum expansion of glaciers in the Sierra Nevada around 30–32 ka BP, predating the global temperature minimum. No data about the environmental evolution is available between 20–30 ka BP. Around 19–20 ka BP glaciers advanced significantly. The process of deglaciation was rapid and around 14–15 ka BP the massif was almost free of ice. The Late Glacial promoted the formation of small glaciers in the highest northern cirques and widespread active periglacial processes (i.e. rock glaciers). During the Holocene there has been an alternation of colder/warmer periods and changing moisture conditions. Periglacial processes have been generally widespread in the summit area, with an increasing or decreasing activity depending on climate conditions. Ephemeral reappearance of small glacial cirques occurred in the highest northern cirques during the coldest and wettest phases. This is the case of the Little Ice Age, as revealed by historical documents and sedimentary records. Since the last decades of the XIX century the temperature has increased ∼0.93°C leading to a decrease of the intensity of periglacial processes in the high lands of the Sierra Nevada.

En este trabajo se estudia el origen de una serie de movimientos en masa, del tipo flujo superficial, ocurridos en la última década en el talud detrítico de la base de la pared septentrional del Pico del Veleta en Sierra Nevada, España (3.398 m 37º03'21''N, 3º21'57''W). La formación de este tipo de coladas se relaciona con la acción geomorfológica de la nieve y con la degradación de hielo en el subsuelo o permafrost. Con este objetivo, se ha realizado un control anual (periodo 1998-2008) de la permanencia y extensión de la cubierta de nieve mediante la toma de fotografías oblicuas a finales del verano y se han observado y cartografiado las variaciones morfológicas del talud en esos años. Los resultados indican que la tendencia reciente de la acumulación y permanencia de la nieve a finales del verano se ha reducido de manera global. Por este motivo, en los últimos años durante los meses estivales el talud permanece libre de la cubierta de nieve, cuya consecuencia más inmediata está siendo la degradación del permafrost existente. La comparación entre el comportamiento de la nieve y los años de formación de flujos superficiales en el talud ha permitido detectar el momento y lugar de la aparición de estos procesos. Los flujos superficiales se forman especialmente en años de un rápido y temprano deshielo de la cubierta nival y lo hacen en los frentes de los neveros más persistentes. Las características sedimentológicas de la masa de derrubios, que contiene abundante material fino, permite en esos momentos la desestabilización de la parte superficial del talud y el despegue y desplazamiento de una delgada capa de material, que tan solo arrastra partículas finas, cantos y pequeños bloques.