A sinkhole, known as a cenote, sink-hole, swallet, swallow hole, or doline, is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes—for example, the dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms, sinkholes may form gradually or suddenly, and are found worldwide. Sinkholes may capture surface drainage from running or standing water, but may form in high. Sinkholes that capture drainage can hold it in limestone caves. These caves may drain into tributaries of larger rivers, the formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion, for example, groundwater may dissolve the carbonate cement holding the sandstone particles together and carry away the lax particles, gradually forming a void.
Occasionally a sinkhole may exhibit a visible opening into a cave below, sinkholes occur in sandstone and quartzite terrains. As the rock dissolves and caverns develop underground and these sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a collapse of the land surface can occur. Sinkholes form from human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places like Louisiana, more commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can occur from the overpumping and extraction of groundwater, sinkholes can form when natural water-drainage patterns are changed and new water-diversion systems are developed. Sinkholes tend to occur in karst landscapes, karst landscapes can have up to thousands of sinkholes within a small area, giving the landscape a pock-marked appearance. These sinkholes drain all the water, so there are only subterranean rivers in these areas, examples of karst landscapes with a plethora of massive sinkholes include Khammouan Mountains and Mamo Plateau.
The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in Venezuela, some sinkholes form in thick layers of homogenous limestone. On the contact of limestone and insoluble rock below it, powerful underground rivers may form, in such conditions, the largest known sinkholes of the world have formed, like the 662-metre deep Xiaozhai Tiankeng, giant sótanos in Querétaro and San Luis Potosí states in Mexico and others. The state of Florida in the United States is known for having frequent sinkhole collapses, the Murge area in southern Italy has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain, an analysis of a case of sinkhole formation under a retention pond due to a large amount of rain can be seen in a sinkhole collapse study
Gorges du Tarn
The Gorges du Tarn is a canyon formed by the Tarn River between the Causse Méjean and the Causse de Sauveterre, in southern France. The canyon, mainly located in the Lozère département, and partially in the Aveyron département, is about 53 kilometres -long and 400 m to 600 m deep, the architecture of the gorges involves Mesozoic limestone plateaux downstream presenting sub-vertical cliffs. Faults like the Hauterive Fault explain the important water sources in the region of Sainte-Enimie, the climate is Mediterranean, with relatively mild winters and very warm summers. Tourism in Tarn Office de Tourisme des Cévennes - Gorges du Tarn Gorges du Tarn on About-France. com
The Causse du Larzac is a limestone karst plateau in the south of the Massif Central, situated between Millau and Lodève. It is an area, where sheep produce milk for Roquefort cheese. Local farmers objected and decided to fight against the project, through such as occupation of empty farms purchased by the Army in anticipation of this expansion. French syndicalist and peasant activist José Bové moved there during this period in support of the protests, communards from the nearby Community of the Ark, led by the pacifist Lanza del Vasto, were very active in opposition to the camp. The workers of the occupied and self-managed Lip factory took part in the movement, following ten years of nonviolent resistance, the plan was cancelled by President François Mitterrand after his election in 1981. Because of its history it was chosen as the site of a meeting against the World Trade Organization which took place in August 2003. José Bové currently resides in Larzac - he secured nearly 500,000 votes in the 2007 presidential elections
Natura 2000 is a network of nature protection areas in the territory of the European Union. It is made up of Special Areas of Conservation and Special Protection Areas designated respectively under the Habitats Directive, the network includes both terrestrial and marine sites. In May 1992, the governments of the European Communities adopted legislation designed to protect the most seriously threatened habitats, the Habitats Directive complements the Birds Directive adopted earlier in 1979 and together they make up the Natura 2000 network of protected areas. The Birds Directive requires the establishment of Special Protection Areas for birds, together, SPAs and SACs form the Natura 2000 network of protected areas. Natura 2000 is a key contribution to the Program of Work of Protected Areas of the Convention on Biological Diversity, as prerequisite for becoming EU Member, accession states have to submit proposals for Natura 2000 sites meeting the same criteria as EU Member States. Some new member states have large areas which qualify to be protected under the directives, the Natura 2000 sites are selected by Member States and the European Commission following strictly scientific criteria according to the two directives mentioned above.
The Habitats Directive divides the EU territory into nine biogeographic regions each with its own ecological coherence, each Natura 2000 site has a unique identification form called Standard Data Form. This form is used as a reference when assessing the management of the species. The Natura 2000 Viewer is a tool to explore the network, Natura 2000 protects around 18 percent of land in the EU countries, and is considered almost complete in the EU terrestrial environment. The process of designation has not always smooth as the infringement procedures against Member States show. While designation of sites may be complete, the management and enforcement of protection on sites is less advanced. Natura 2000 faced criticism from developers and politicians who fear that the conservation of habitats,251,564 km squared had been designated as Natura 2000 in the marine environment in 2013. The network in areas is not considered complete and acknowledged by the Commission as a “key challenge for EU biodiversity policy in the coming years”.
Natura 2000 sites can vary considerably in character and they are not strictly protected in terms of how they are allowed to be used by people. Many sites are farmed and some are even in urban areas, the European Commission developed guidelines on the relation between Natura 2000 and wild areas which are thought to make up around 13% of the network. This was in response to a report by Members of the European Parliament in 2009 which called for protection of Europes wilderness. The Natura 2000 network is not well known among European citizens, as part of the EU Biodiversity Strategy, the European Commission committed to raise awareness about the network and biodiversity in general with the public. In order to raise awareness about the Natura 2000 network,21 May has been designated “Natura 2000 Day” and this precedes “International Day for Biological Diversity” on 22 May
A canyon or gorge is a deep cleft between escarpments or cliffs resulting from the erosive activity of a river over geologic timescales. A canyon may refer to a rift between two peaks, such as those in ranges including the Rocky Mountains, the Alps. Usually a river or stream and erosion carve out such splits between mountains, examples of mountain-type canyons are Provo Canyon in Utah or Yosemite National Park in Californias Sierra Nevada. Canyons within mountains, or gorges that have an opening on one side are called box canyons. Slot canyons are very narrow canyons, often with smooth walls, steep-sided valleys in the seabed of the continental slope underwater are referred to as submarine canyons. Unlike canyons on land, submarine canyons are thought to be formed by turbidity currents, the word canyon is Spanish in origin, with the same meaning. The word canyon is used in North America while the words gorge and ravine are used in Europe and Oceania, though gorge. In the United States, place names generally use canyon in the southwest and gorge in the northeast, in Canada, a gorge is usually narrow while a ravine is more open and often wooded.
The military-derived word defile is occasionally used in the United Kingdom, most canyons were formed by a process of long-time erosion from a plateau or table-land level. The cliffs form because harder rock strata that are resistant to erosion, Canyons are much more common in arid than in wet areas because physical weathering has a more localized effect in arid zones. The wind and water from the combine to erode and cut away less resistant materials such as shales. The freezing and expansion of water serves to help form canyons, water seeps into cracks between the rocks and freezes, pushing the rocks apart and eventually causing large chunks to break off the canyon walls, in a process known as frost wedging. Canyon walls are formed of resistant sandstones or granite. Sometimes large rivers run through canyons as the result of geological uplift. These are called entrenched rivers, because they are unable to alter their course. In the United States, the Colorado River in the Southwest, Canyons often form in areas of limestone rock.
As limestone is soluble to an extent, cave systems form in the rock. When these collapse, a canyon is left, as in the Mendip Hills in Somerset and Yorkshire Dales in Yorkshire, England
The Causses are a group of limestone plateaus in the Massif Central. They are bordered to the north-west by the Limousin and the Périgord uplands, and to the east by the Aubrac, large river gorges cut through the plateau, such as the Tarn, Jonte and Aveyron. Causse is an Occitan word meaning limestone plateau, the Causses and the Cévennes, Mediterranean agro-pastoral Cultural Landscape was added to the UNESCO World Heritage list in 2011
Aubrac is a small village in the southern Massif Central of France. The name is applied to the surrounding countryside, which is properly called LAubrac in French. The Aubrac region has been a member of the Natura 2000 network since August 2006 and it straddles three départements - Cantal and Lozère - and three régions - Auvergne, Midi-Pyrénées and Languedoc-Roussillon. Aubrac is a volcanic and granitic plateau that extends over an area of 1,500 km2, the volcanic eruptions occurred between 6 and 9 million year ago and were of Hawaiian type with fluid lavas. There are therefore no individual volcanic cones, the volcanic zone occupies the west side while the other part of the plateau is formed of granite. The average altitude is about 1,200 meters with the highest point at 1,469 meters in the south, all the region has been eroded by glaciers during three glacial periods. The Aubrac includes four lakes, lac des Salhiens, lac de Saint-Andéol, lac de Souveyrols. In the south, the highest summits of the Aubrac dominate the Lot valley, bovine breeding is the main activity on the plateau.
Aubrac has its own bovine species called Aubrac, which is adapted to the environment. The cows are bred for their meat while, before the 1960s, the milk was made into cheese in burons or mazucs, which are small structures in the middle of the pastures. Today, the majority of structures are in ruin. The Laguiole cheese is made by a dairy in the village of Laguiole, the region is known for its knife industry. It is here that the Laguiole knife is made by around thirty local craftsmen, the factory of Forge de Laguiole was designed by Phillippe Starck. By 1000 BC, the Celts had occupied the region, in the period of Roman Gaul, Gaulish tribes called Gabalians and Rutènians occupied the area. Julius Caesar stated that the Gabalians were survivors of the Battle of Alesia, the Rutenians, who may have come from the Danube delta and who gave their name to the Rouergue, became allied with Vercingetorix. In the early Middle Ages, Grégory of Tours recorded an incident of a Pagan rite at the lake near Mount Hélanus.
Later, a pilgrim of St. James, survived after a fight in the area, the village of Aubrac grew around the hospital. The Dômerie was home to monks and the knights of the Order of Aubrac until the French Revolution, the monks fed and sheltered passing pilgrims, and rang a Bell of the Lost during times of snow
Limousin is a former administrative region of France. Since 1 January 2016, it is part of the new region Nouvelle Aquitaine and it was composed of three departments, Corrèze, Creuse and Haute-Vienne. Situated largely in the Massif Central, as of January 1,2010, forming part of the southwest of France, Limousin is bordered by the regions of Centre to the north, Poitou-Charentes and Aquitaine to the west, Midi-Pyrénées to the south and Auvergne to the east. Limousin is part of Occitania, the modern region of Limousin is essentially composed of two historical French provinces, the department of Corrèze in its entirety and the central and southeastern part of Haute-Vienne. The entire old province of Limousin is contained within the modern Limousin, most of the department of Creuse and the north of Haute-Vienne. The old province of Marche is almost entirely contained within the region of Limousin. Limoges, the capital and largest city of the province of Limousin, is the capital of the Limousin administrative region.
With a slowly rising population of just under 750,000, the population of Limousin is aging and, until 1999, was declining. The department of Creuse has the oldest population of any in France, between 1999 and 2004 the population of Limousin increased slightly, reversing a decline for the first time in decades. Brive-la-Gaillarde Guéret Limoges Panazol Saint-Junien Tulle Ussel Limousin is a rural region. Famed for some of the best beef farming in the world, the region is a major timber producing area. It is a partnership that is over 100 years old, the regional capital, was once an industrial power base, world-renowned for its porcelain and still a leader and innovator in electric equipment factories. However, large factories are now few in number, some of the rivers belonging to the Loire basin run through the north and east of the region, waterways belonging to that of the Dordogne through the south. The region is crossed by three rivers, the Vienne, the Dordogne and the Charente. The region is known for the high quality of its water.
The Limousin region is almost entirely an upland area, the lowest land is in the northwest of the region and the highest land is roughly in the southeast. However, the part of the region is above 350 m. Limousin is one of the provinces of France