Landscapes due to rock spreading and block sliding: natural fortresses, sacred sites, valuable archaeological and scenic resources

Lateral spreading and block sliding are often associated in nature causing large rock blocks to progressively separate from a cliff (i.e. lateral spreading) and slowly slide down the slope of a hillside (i.e. block sliding). These large landslides generate landscapes with distinctive landforms that have been valued as part of the geological heritage for a series of reasons among which the interaction with human activities through time. We highlight this relationship by describing several examples studied in recent years in Spain, Tunisia and Malta and discussing the heritage value this type of places could possess.

In Spain, La Peña de los Gitanos (Granada) is a hill widely known in its surrounding area for its numerous archaeological sites but not so much for its geomorphological singularity, something that did attract its ancient settlers. The south western slope of the hill presents a peculiar aspect caused by the lateral displacement and sliding of calcarenite blocks over marls. The slope shows large open crevices, vertical rock walls, alleys and close depressions making up a ruiniform landscape full of passages and hiding places creating a natural fortress. These morphological features must have been valued by the ancient communities that settled here for at least five thousand years, from the Early Neolithic to the Middle Ages. These settlements exploited the easy defence of the site and dolmens and necropolises reflect the spiritual dimension assigned to the site. In Tunisia there is one of the most spectacular examples of lateral spreading and block slide of the Mediterranean region, the Chgega Mountain (Mateur). Its most striking geomorphic feature is that right at its crest there is a large, vertical-walled depression filled with large limestone blocks that are tilted and separated from each other by large, open discontinuities. This gravity-induced depression creates a site of great contrast with the surroundings and the rock blocks inside produce a landscape full of passages, natural alleys and nooks and crannies where wildlife finds refuge from the arid vicinity. Chgega also has archaeological sites with remains from the Roman period which are now abandoned and suffer from continuous looting due to lack of protection. With its spectacular scenery and sites, Chgega looks like a place that could have been prominent in the past but has fallen into oblivion. In Malta, the landforms due to lateral spreading and block sliding observed in Il-Majjistral Nature and History Park are the main responsible of its scenery and give it a special character. This location is a natural laboratory where the above-mentioned processes are being investigated and described with a great detail during the last decade. The three sites are places where currently hiking and climbing activities take place and they continue to attract people because of its scenery or even spiritual background.

 

Keywords: Lateral spreads, Block Sliding; Slope processes; Geoarchaeology, Mediterranean