Karst is a topography formed from the dissolution of soluble rocks such as limestone and gypsum. It is characterized by underground drainage systems with caves, it has been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no lakes. However, in regions where the dissolved bedrock is covered or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and be missing above ground; the study of karst is considered of prime importance in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in porous karst systems. The English word karst was borrowed from German Karst in the late 19th century, which entered German much earlier. According to one interpretation the term is derived from the German name for a number of geological and hydrological features found within the range of the Dinaric Alps, stretching from the northeastern corner of Italy above the city of Trieste, across the Balkan peninsula along the coast of the eastern Adriatic to Kosovo and North Macedonia, where the massif of the Šar Mountains begins, more the karst zone at the northwestern-most section, described in early topographical research as a plateau, between Italy and Slovenia.
In the local South Slavic languages, all variations of the word are derived from a Romanized Illyrian base metathesized from the reconstructed form *korsъ into forms such as Bosnian: krš, Croatian: krš, kraš, Serbian: kras, Slovene: kras. Languages preserving the older, non-metathesized form include Italian: Carso, German: Karst, Albanian: karsti; the Slovene common noun kras was first attested in the 18th century, the adjective form kraški in the 16th century. As a proper noun, the Slovene form Grast was first attested in 1177; the word is of Mediterranean origin. It has been suggested that the word may derive from the Proto-Indo-European root karra-'rock'; the name may be connected to the oronym Karsádios oros cited by Ptolemy, also to Latin Carusardius. Johann Weikhard von Valvasor, a pioneer of the study of karst in Slovenia and a fellow of the Royal Society for Improving Natural Knowledge, introduced the word karst to European scholars in 1689, describing the phenomenon of underground flows of rivers in his account of Lake Cerknica.
Jovan Cvijić advanced the knowledge of karst regions, so much that he became known as the "father of karst geomorphology". Discussing the karstic regions of the Balkans, Cvijić's 1893 publication Das Karstphänomen describes landforms such as karren and poljes. In a 1918 publication, Cvijić proposed a cyclical model for karstic landscape development. Karst hydrology emerged as a discipline in early 1960s in France; the activities of cave explorers, called speleologists, had been dismissed as more of a sport than a science, meaning that underground karstic caves and their associated watercourses were, from a scientific perspective, understudied. The development of karst occurs whenever acidic water starts to break down the surface of bedrock near its cracks, or bedding planes; as the bedrock continues to degrade, its cracks tend to get bigger. As time goes on, these fractures will become wider, a drainage system of some sort may start to form underneath. If this underground drainage system does form, it will speed up the development of karst formations there because more water will be able to flow through the region, giving it more erosive power.
The carbonic acid that causes karstic features is formed as rain passes through Earth's atmosphere picking up carbon dioxide, which dissolves in the water. Once the rain reaches the ground, it may pass through soil that can provide much more CO2 to form a weak carbonic acid solution, which dissolves calcium carbonate; the primary reaction sequence in limestone dissolution is the following: In particular and rare conditions such as encountered in the past in Lechuguilla Cave in New Mexico, other mechanisms may play a role. The oxidation of sulfides leading to the formation of sulfuric acid can be one of the corrosion factors in karst formation; as oxygen -rich surface waters seep into deep anoxic karst systems, they bring oxygen, which reacts with sulfide present in the system to form sulfuric acid. Sulfuric acid reacts with calcium carbonate, causing increased erosion within the limestone formation; this chain of reactions is: This reaction chain forms gypsum. The karstification of a landscape may result in a variety of large- or small-scale features both on the surface and beneath.
On exposed surfaces, small features may include solution flutes, limestone pavement, collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes, vertical shafts, disappearing streams, reappearing springs. Large-scale features may include limestone pavements and karst valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers, or haystack/eggbox landscapes. Beneath the surface, complex underground drainage systems and extensive caves and cavern systems may form. Erosion along limes
Monte Santo (Siligo)
Monte Santo is an isolated mountain and a mesa in northern Sardinia, Italy, in the province of Sassari, in the region of Logudoro. It has an elevation of 733 metres; the most substantial portion of the mountain is located in the territory of Siligo. However, some parts belong to the comunes Ardara and Mores. On the flat of the mountain stands the church of St. Elias and st. Enoch, who appeared in the list of goods in the gift, made in favor of the abbey of Montecassino in eleventh century from Judge Barisone I of Torres Sardegna Cultura - The church of the st. Elijah and Enoch
Graniti is a comune in the Province of Messina in the Italian region Sicily, located about 160 kilometres east of Palermo and about 45 kilometres southwest of Messina. As of 31 December 2004, it had a population of 1,550 and an area of 10.0 square kilometres. Graniti borders the following municipalities: Antillo, Castiglione di Sicilia, Mongiuffi Melia, Motta Camastra
Mount Arcuentu, elevation 785 m, is a volcanic massif situated in southwestern Sardinia, northwest of Arbus. It is a summit of a mountain range which runs parallel to the coastline of Costa Verde for about 8 kilometres. Arbus, Sardinia Costa Verde Montevecchio Province of Medio Campidano Ignazio Camarda, Montagne di Sardegna, Carlo Delfino, 1993. ISBN 88-7138-072-X. Bacchetta, C. Pontecorvo. La flora del Monte Arcuentu. Webbia 62: 175-204
Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy. It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Holocene; the informal term "Late Quaternary" refers to the past 0.5–1.0 million years. The Quaternary Period is defined by the cyclic growth and decay of continental ice sheets associated with Milankovitch cycles and the associated climate and environmental changes that occurred. In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders"; the term "quaternary" was introduced by Jules Desnoyers in 1829 for sediments of France's Seine Basin that seemed to be younger than Tertiary Period rocks. The Quaternary Period extends to the present; the Quaternary covers the time span of glaciations classified as the Pleistocene, includes the present interglacial time-period, the Holocene.
This places the start of the Quaternary at the onset of Northern Hemisphere glaciation 2.6 million years ago. Prior to 2009, the Pleistocene was defined to be from 1.805 million years ago to the present, so the current definition of the Pleistocene includes a portion of what was, prior to 2009, defined as the Pliocene. Quaternary stratigraphers worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy tried to make a single geologic time scale based on GSSP's, which could be used internationally; the Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate. This led to the problem that the proposed base of the Pleistocene was at 1.805 Mya, long after the start of the major glaciations of the northern hemisphere. The ICS proposed to abolish use of the name Quaternary altogether, which appeared unacceptable to the International Union for Quaternary Research. In 2009, it was decided to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.588 Mya and including the Gelasian stage, considered part of the Neogene Period and Pliocene Epoch.
The Anthropocene has been proposed as a third epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution, or about 200 years ago. The Anthropocene is not designated by the ICS, but a working group has been working on a proposal for the creation of an epoch or sub-period; the 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this geologically short time period, there has been little change in the distribution of the continents due to plate tectonics; the Quaternary geological record is preserved in greater detail than that for earlier periods. The major geographical changes during this time period included the emergence of the Strait of Bosphorus and Skagerrak during glacial epochs, which turned the Black Sea and Baltic Sea into fresh water, followed by their flooding by rising sea level; the current extent of Hudson Bay, the Great Lakes and other major lakes of North America are a consequence of the Canadian Shield's readjustment since the last ice age.
The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. There was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mastodons, etc. became extinct worldwide. Others, including horses and American cheetahs became extinct in North America. Glaciation took place during the Quaternary Ice Age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present day. In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a considerable distance from the Alps; this idea was disputed by another Swiss scientist, Louis Agassiz, but when he undertook to disprove it, he ended up affirming his colleague's hypothesis. A year Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects.
This idea led to the establishment of the Glacial Theory. In time, thanks to the refinement of geology, it has been demonstrated that there were several periods of glacial advance and retreat and that past temperatures on Earth were different from today. In particular, the Milankovitch cycles of Milutin Milankovitch are based on the premise that variations in incoming solar radiation are a fundamental factor controlling Earth's climate. During this time, substantial glaciers advanced and retreated over much of North America and Europe, parts of South America and Asia, all of Antarctica; the Great Lakes formed and giant mammals thrived in parts of North America and Eurasia not covered in ice. These mammals became extinct. Modern humans evolved about 315,000 years ago. During the Quaternary Period, flowering plants, insects dominated
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock is subjected to pressure, causing profound physical or chemical change; the protolith may be igneous, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface, they are classified by chemical and mineral assemblage. They may be formed by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it, they can form from tectonic processes such as continental collisions, which cause horizontal pressure and distortion. They are formed when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior; the study of metamorphic rocks provides information about the temperatures and pressures that occur at great depths within the Earth's crust. Some examples of metamorphic rocks are gneiss, marble and quartzite.
Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as index minerals, include sillimanite, staurolite and some garnet. Other minerals, such as olivines, amphiboles, micas and quartz, may be found in metamorphic rocks, but are not the result of the process of metamorphism; these minerals formed during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are stable only within certain limits, the presence of some minerals in metamorphic rocks indicates the approximate temperatures and pressures at which they formed; the change in the particle size of the rock during the process of metamorphism is called recrystallization. For instance, the small calcite crystals in the sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble. Both high temperatures and pressures contribute to recrystallization.
High temperatures allow the atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. The layering within metamorphic rocks is called foliation, it occurs when a rock is being shortened along one axis during recrystallization; this causes the platy or elongated crystals of minerals, such as mica and chlorite, to become rotated such that their long axes are perpendicular to the orientation of shortening. This results in a banded, or foliated rock, with the bands showing the colors of the minerals that formed them. Textures are separated into non-foliated categories. Foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage. For example, slate is a foliated metamorphic rock. Non-foliated rock does not have planar patterns of strain. Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth habits, will not be foliated.
Where a rock has been subject to differential stress, the type of foliation that develops depends on the metamorphic grade. For instance, starting with a mudstone, the following sequence develops with increasing temperature: slate is a fine-grained, foliated metamorphic rock, characteristic of low grade metamorphism, while phyllite is fine-grained and found in areas of low grade metamorphism, schist is medium to coarse-grained and found in areas of medium grade metamorphism, gneiss coarse to coarse-grained, found in areas of high-grade metamorphism. Marble is not foliated, which allows its use as a material for sculpture and architecture. Another important mechanism of metamorphism is that of chemical reactions that occur between minerals without them melting. In the process atoms are exchanged between the minerals, thus new minerals are formed. Many complex high-temperature reactions may take place, each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism.
Metasomatism is the drastic change in the bulk chemical composition of a rock that occurs during the processes of metamorphism. It is due to the introduction of chemicals from other surrounding rocks. Water may transport these chemicals over great distances; because of the role played by water, metamorphic rocks contain many elements absent from the original rock, lack some that were present. Still, the introduction of new chemicals is not necessary for recrystallization to occur. Contact metamorphism is the name given to the changes that take place when magma is injected into the surrounding solid rock; the changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact metamorphism aureole. Aureoles may show all degrees of metamorphism from the contact area to unmetamorphosed country rock some distance away.
The formation of important ore minerals may o
Monte Corrasi is a mountain in the territory of Oliena, Province of Nuoro, eastern Sardinia, Italy. It is a massif formed by white limestone