Limestone is a carbonate sedimentary rock, composed of the skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. A related rock is dolostone, which contains a high percentage of the mineral dolomite, CaMg2. In fact, in old USGS publications, dolostone was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolostones or magnesium-rich limestones. About 10% of sedimentary rocks are limestones; the solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses: as a building material, an essential component of concrete, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as foraminifera; these organisms secrete shells made of aragonite or calcite, leave these shells behind when they die. Other carbonate grains composing limestones are ooids, peloids and extraclasts. Limestone contains variable amounts of silica in the form of chert or siliceous skeletal fragment, varying amounts of clay and sand carried in by rivers; some limestones do not consist of grains, are formed by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters; this produces speleothems, such as stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance; the primary source of the calcite in limestone is most marine organisms. Some of these organisms can construct mounds of rock building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone does not form in deeper waters.
Limestones may form in lacustrine and evaporite depositional environments. Calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors with weathered surfaces. Limestone may be crystalline, granular, or massive, depending on the method of formation. Crystals of calcite, dolomite or barite may line small cavities in the rock; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite.
Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process, limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. Two major classification schemes, the Folk and the Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems and cement; the Folk system uses two-part names. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample; the Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains. Robert J. Dunham published his system for limestone in 1962.
Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are for rock families, his efforts deal with the question of whether or not the grains were in mutual contact, therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock; the Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright, it adds some diagenetic patterns and can be summarized as follows: See: Carbonate platform About 10% of all sedimentary rocks are limestones. Limestone is soluble in acid, therefore forms many erosional landforms; these include limestone pavements, pot holes, cenotes and gorges. Such erosion landscapes are known
Liberal Democratic Party of Moldova
The Liberal Democratic Party of Moldova is a conservative political party in Moldova. The party is led by a former Minister of Defense of Moldova; until 2016, PLDM was led by Vlad Filat, Prime Minister of Moldova from 2009 to 2013, in two cabinets. After the 2014 parliamentary elections, with 21 seats in the Moldovan Parliament, PLDM was the largest of the three democratic pro-European parliamentary parties; the party's founding congress was held on 8 December 2007 and Vlad Filat was elected as president. The initiative group of the party was centered on Filat, a prominent member of the Democratic Party of Moldova, disappointed with the direction taken by that political party under Dumitru Diacov's leadership. Soon, a lot of local branches of the Christian Democratic Popular Party, disappointed with Iurie Roşca's policy of cooperation with the Communist Party of Moldova, joined PLDM en masse; the party attracted many of prominent members of civil society. At its first election, in April 2009, PLDM won 15 seats, which increased to 18 three months after which Filat became the Prime Minister, leading the Alliance for European Integration.
In November 2010, the PLDM jumped to 32 seats. The AIE was replaced by the Pro-European Coalition in 2013, when Iurie Leancă replaced Filat as Prime Minister, with Filat remaining as the party chairman. On October 8, 2007, the initiative group composed of 53 leaders renowned in their fields, launched the idea of creating the Liberal Democratic Party of Moldova; the leaders of the group included: Vlad Filat, Deputy in the Parliament of the Republic of Moldova. In their statements, the initiative group members acknowledged the profound crisis in the Republic of Moldova and the inability of political parties to face the situation; the Liberal Democratic Party of Moldova emerged as a capable alternative to start the process of moral reorganization of the political class and modernization of the country, reestablishment of the society back on its natural track of democratic development. For two months, over 20,000 citizens from all districts of the country submitted applications to join the Liberal Democratic Party.
Organizations were created in all territorial-administrative units of the second level in Chişinău, Bălţi, Tiraspol and Gagauzia. The first founding Congress of the Liberal Democratic Party of Moldova took place on December 8, 2007 in Chişinău, it was attended by 592 delegates from 38 local organizations. The Congress approved the Program and Statute and elected the governing and control bodies of the party; the second Congress of the Liberal Democratic Party of Moldova took place on September 27, 2008, in Balti. It was attended by 547 delegates from local party organizations; the Congress debated the issues related to the work of the Liberal Democratic Party of Moldova between the congresses and supplementing the Statute of PLDM, as well as issues related to Moldova current domestic situation. The Liberal Democratic Teachers Association was formed within the party on September 13, 2008 and on October 11, 2008 – the Liberal Democratic Doctors and Pharmacists Association. Formation of socio-professional associations within the party is stipulated in the statute of the Liberal Democratic Party of Moldova.
The Founding Conference of the Youth Organization of the Liberal Democratic Party of Moldova took place on November 15, 2008. It was attended by 517 delegates from all country districts; the delegates at the conference approved the Regulation of the Youth Organization of the Liberal Democratic Party of Moldova and elected the administration of the organization. The Conference approved the "Green Charter for Youth" - a programmatic document that includes solutions to key issues that young people face. On December 27, 2008, the Liberal Democratic Women's Organization was created within the PLDM, on January 24, 2009 – the Association of Elderly Persons; the Liberal Democratic Association of People active in the cultural field was created on January 31, 2008 within the framework of the party. At the parliamentary elections of April 5, 2009, PLDM obtained 12.43% of the votes, with 15 seats in the Parliament of Moldova. At the early elections of July 29, PLDM gained 16.57% of the votes and was represented in the Parliament by 18 deputies.
Together with deputies from the LP, DPM and AMN, the Liberal Democratic Party of Moldova formed the new majority coalition in the Legislative - the Alliance for European Integration. On September 25, 2009, the Parliament gave the vote of trust to the Government and Prime Minister Vlad Filat, president of PLDM. Besides the Prime Minister, PLDM is represented in the government by six ministers: Iurie Leanca, Alexandru Tanase, Veaceslav Negrută, Victor Bodiu, Vladimir Hotineanu, Victor Catan; the Third Extraordinary Congress of the PLDM took place on December 2009 in Chişinău. It was attended by 1,800 delegates from local party
Clay is a finely-grained natural rock or soil material that combines one or more clay minerals with possible traces of quartz, metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to particle size and geometry as well as water content, become hard and non–plastic upon drying or firing. Depending on the soil's content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, some overlap in particle size and other physical properties; the distinction between silt and clay varies by discipline. Geologists and soil scientists consider the separation to occur at a particle size of 2 µm, sedimentologists use 4–5 μm, colloid chemists use 1 μm.
Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 silt particles as being larger. Mixtures of sand and less than 40% clay are called loam. Loam is used as a building material. Clay minerals form over long periods of time as a result of the gradual chemical weathering of rocks silicate-bearing, by low concentrations of carbonic acid and other diluted solvents; these solvents acidic, migrate through the weathering rock after leaching through upper weathered layers. In addition to the weathering process, some clay minerals are formed through hydrothermal activity. There are two types of clay deposits: secondary. Primary clays remain at the site of formation. Secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with low energy depositional environments such as large lakes and marine basins.
Depending on the academic source, there are three or four main groups of clays: kaolinite, montmorillonite-smectite and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a separate group within the phyllosilicates. There are 30 different types of "pure" clays in these categories, but most "natural" clay deposits are mixtures of these different types, along with other weathered minerals. Varve is clay with visible annual layers, which are formed by seasonal deposition of those layers and are marked by differences in erosion and organic content; this type of deposit is common in former glacial lakes. When fine sediments are delivered into the calm waters of these glacial lake basins away from the shoreline, they settle to the lake bed; the resulting seasonal layering is preserved in an distribution of clay sediment banding. Quick clay is a unique type of marine clay indigenous to the glaciated terrains of Norway, Northern Ireland, Sweden, it is a sensitive clay, prone to liquefaction, involved in several deadly landslides.
Powder X-ray diffraction can be used to identify clays. The physical and reactive chemical properties can be used to help elucidate the composition of clays. Clays exhibit plasticity. However, when dry, clay becomes firm and when fired in a kiln, permanent physical and chemical changes occur; these changes convert the clay into a ceramic material. Because of these properties, clay is used for making pottery, both utilitarian and decorative, construction products, such as bricks and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware and porcelain. Prehistoric humans discovered the useful properties of clay; some of the earliest pottery shards recovered are from Japan. They are associated with the Jōmon culture and deposits they were recovered from have been dated to around 14,000 BC. Clay tablets were the first known writing medium. Scribes wrote by inscribing them with cuneiform script using a blunt reed called a stylus. Purpose-made clay balls were used as sling ammunition.
Clays sintered in fire were the first form of ceramic. Bricks, cooking pots, art objects, smoking pipes, musical instruments such as the ocarina can all be shaped from clay before being fired. Clay is used in many industrial processes, such as paper making, cement production, chemical filtering; until the late 20th century, bentonite clay was used as a mold binder in the manufacture of sand castings. Clay, being impermeable to water, is used where natural seals are needed, such as in the cores of dams, or as a barrier in landfills against toxic seepage. Studies in the early 21st century have investigated clay's absorption capacities in various applications, such as the removal of heavy metals from waste water and air purification. Traditional uses of clay as medicine goes back to prehistoric times. An example is Armenian bole, used to soothe an upset stomach; some animals such as parrots and pigs ingest clay for similar reasons. Kaolin clay and attapulgite have been used as anti-diarrheal medicines.
Clay as the defining ingredient of loam is one of the oldest building materials on Earth, among other
Șaptebani is a village in Rîșcani District, Moldova. The village centre is located at an altitude of 171 meters. Șaptebani was first mentioned in documents in 1425. There is a World War II memorial in the central square; the local geography of open plains broken by rolling hills and gullies show a major tank battle, with many thousands killed. After the war, some of the local inhabitants were deported to Siberia for up to 15 years. In an unusual gesture, the local school conferred honorary degrees on the returnees. A wooden church was built between 1904 and 1906; the entrance has a large Byzantine-style painting on the town on a mural in tempera, without knowing painter. In 1944, when the Soviet Army entered the area, the church was closed, the priest was intimidated and abused. Although it reopened for a short period in 1954-1957, it closed in 1957 upon the death of the priest, although it reopened in autumn 1990. Gheorghe Tudor
Bessarabia is a historical region in Eastern Europe, bounded by the Dniester river on the east and the Prut river on the west. About two thirds of Bessarabia lies within modern-day Moldova, with the Ukrainian Budjak region covering the southern coastal region and part of the Ukrainian Chernivtsi Oblast covering a small area in the north. In the aftermath of the Russo-Turkish War, the ensuing Peace of Bucharest, the eastern parts of the Principality of Moldavia, an Ottoman vassal, along with some areas under direct Ottoman rule, were ceded to Imperial Russia; the acquisition was among the Empire's last territorial acquisitions in Europe. The newly acquired territories were organised as the Governorate of Bessarabia, adopting a name used for the southern plains, between the Dniester and the Danube rivers. Following the Crimean War, in 1856, the southern areas of Bessarabia were returned to Moldavian rule. In 1917, in the wake of the Russian Revolution, the area constituted itself as the Moldavian Democratic Republic, an autonomous republic part of a proposed federative Russian state.
Bolshevik agitation in late 1917 and early 1918 resulted in the intervention of the Romanian Army, ostensibly to pacify the region. Soon after, the parliamentary assembly declared independence, union with the Kingdom of Romania; the legality of these acts was however disputed, most prominently by the Soviet Union, which regarded the area as a territory occupied by Romania. In 1940, after securing the assent of Nazi Germany through the Molotov–Ribbentrop Pact, the Soviet Union pressured Romania, under threat of war, into withdrawing from Bessarabia, allowing the Red Army to annex the region; the area was formally integrated into the Soviet Union: the core joined parts of the Moldavian ASSR to form the Moldavian SSR, while territories inhabited by Slavic majorities in the north and the south of Bessarabia were transferred to the Ukrainian SSR. Axis-aligned Romania recaptured the region in 1941 with the success of Operation München during the Nazi invasion of the Soviet Union, but lost it in 1944 as the tide of war changed.
In 1947, the Soviet-Romanian border along the Prut was internationally recognised by the Paris Treaty that ended World War II. During the process of the dissolution of the Soviet Union, the Moldavian and Ukrainian SSRs proclaimed their independence in 1991, becoming the modern states of Moldova and Ukraine, while preserving the existing partition of Bessarabia. Following a short war in the early 1990s, the Pridnestrovian Moldavian Republic was proclaimed in the Transnistria, extending its authority over the municipality of Bender on the right bank of Dniester river. Part of the Gagauz-inhabited areas in the southern Bessarabia was organised in 1994 as an autonomous region within Moldova. According to the traditional explanation, the name Bessarabia derives from the Wallachian Basarab dynasty, who ruled over the southern part of the area in the 14th century; some scholars question this, claiming that: the name was an exonym applied by Western cartographers it was first used in local sources only in the late 17th century.
According to Dimitrie Cantemir, the name Bessarabia applied only to the part of the territory south of the Upper Trajanic Wall, i.e. an area only bigger than present-day Budjak. The region is bounded by the Dniester to the north and east, the Prut to the west and the lower River Danube and the Black Sea to the south, it has an area of 45,630 km2. The area is hilly plains with flat steppes, it is fertile, has lignite deposits and stone quarries. People living in the area grow sugar beet, wheat, tobacco, wine grapes and fruit, they raise sheep and cattle. The main industry in the region is agricultural processing; the region's main cities are Chișinău, Izmail and Bilhorod-Dnistrovs'kyi called Cetatea Albă / Akkerman. Other towns of administrative or historical importance include: Khotyn and Kilia, Lipcani, Soroca, Bălți, Ungheni, Bender/Tighina and Cahul. In the late 14th century, the newly established Principality of Moldavia encompassed what became known as Bessarabia. Afterwards, this territory was directly or indirectly or wholly controlled by: the Ottoman Empire, Russian Empire, the USSR.
Since 1991, most of the territory forms the core of Moldova, with smaller parts in Ukraine. The territory of Bessarabia has been inhabited by people for thousands of years. Cucuteni–Trypillia culture flourished between the 6th and 3rd millennium BC. In Antiquity the region was inhabited by Thracians, as well as for shorter periods by Cimmerians, Scythians and Celts by tribes such as the Costoboci, Britogali and Bastarnae. In the 6th century BC
Gravel is a loose aggregation of rock fragments. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular pebble gravel. ISO 14688 grades gravels as fine and coarse with ranges 2 mm to 6.3 mm to 20 mm to 63 mm. One cubic metre of gravel weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with tarmac. Both sand and small gravel are important for the manufacture of concrete. Large gravel deposits are a common geological feature, being formed as a result of the weathering and erosion of rocks; the action of rivers and waves tends to pile up gravel in large accumulations. This can sometimes result in gravel becoming compacted and lithified into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, or basalt.
Quarries where gravel is extracted are known as gravel pits. Southern England possesses large concentrations of them due to the widespread deposition of gravel in the region during the Ice Ages; as of 2006, the United States is consumer of gravel. The word gravel comes from the Breton language. In Breton, "grav" means coast. Adding the "-el" suffix in Breton denotes the component parts of something larger, thus "gravel" means the small stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravelle. Gravel has the meaning a mixture of different size pieces of stone mixed with sand and some clay. In American English, rocks broken into small pieces by a crusher are known as crushed stone. Types of gravel include: Bank gravel: deposited gravel intermixed with sand or clay found in and next to rivers and streams. Known as "bank run" or "river run". Bench gravel: a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level.
Creek rock or river rock: this is rounded, semi-polished stones of a wide range of types, that are dredged or scooped from stream beds. It is often used as concrete aggregate and less as a paving surface. Crushed stone: rock crushed and graded by screens and mixed to a blend of stones and fines, it is used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone and other rocks. Known as "crusher run", DGA QP, shoulder stone. Fine gravel: gravel consisting of particles with a diameter of 2 to 8 mm. Stone dust: fine, gravel from the final stage of screen separation, such that the gravel is not separated out from fine dust particles. Lag gravel: a surface accumulation of coarse gravel produced by the removal of finer particles. Pay gravel: known as "pay dirt"; the metals are recovered through gold panning. Pea gravel: known as "pea shingle" is gravel that consists of small, rounded stones used in concrete surfaces. Used for walkways, driveways and as a substrate in home aquariums.
Piedmont gravel: a coarse gravel carried down from high places by mountain streams and deposited on flat ground, where the water runs more slowly. Plateau gravel: a layer of gravel on a plateau or other region above the height at which stream-terrace gravel is found. In locales where gravelly soil is predominant, plant life is more sparse; this outcome derives from the inferior ability of gravels to retain moisture, as well as the corresponding paucity of mineral nutrients, since finer soils that contain such minerals are present in smaller amounts. Construction aggregate Pebble Rock Media related to Gravel at Wikimedia Commons
Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than coarser than silt. Sand can refer to a textural class of soil or soil type; the composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica in the form of quartz. The second most common type of sand is calcium carbonate, for example, created, over the past half billion years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non-renewable resource over human timescales, sand suitable for making concrete is in high demand. Desert sand, although plentiful, is not suitable for concrete, 50 billion tons of beach sand and fossil sand is needed each year for construction; the exact definition of sand varies.
The scientific Unified Soil Classification System used in engineering and geology corresponds to US Standard Sieves, defines sand as particles with a diameter of between 0.074 and 4.75 millimeters. By another definition, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this range size is termed a sand grain. Sand grains are between silt; the size specification between sand and gravel has remained constant for more than a century, but particle diameters as small as 0.02 mm were considered sand under the Albert Atterberg standard in use during the early 20th century. The grains of sand in Archimedes Sand Reckoner written around 240 BCE, were 0.02 mm in diameter. A 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A 1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers.
Silt, by comparison, feels like flour). ISO 14688 grades sands as fine and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is divided into five sub-categories based on size: fine sand, fine sand, medium sand, coarse sand, coarse sand; these sizes are based on the Krumbein phi scale, where size in Φ = -log2D. On this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers; the most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica in the form of quartz, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering. The composition of mineral sand is variable, depending on the local rock sources and conditions; the bright white sands found in tropical and subtropical coastal settings are eroded limestone and may contain coral and shell fragments in addition to other organic or organically derived fragmental material, suggesting sand formation depends on living organisms, too.
The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, white color. Arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop; some sands contain magnetite, glauconite or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are green in color, as are sands derived from basaltic lava with a high olivine content. Many sands those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones. Rocks erode/weather over a long period of time by water and wind, their sediments are transported downstream; these sediments continue to break apart into smaller pieces. The type of rock the sediment originated from and the intensity of the environment gives different compositions of sand.
The most common rock to form sand is Granite, where the Feldspar minerals dissolve faster than the Quartz, causing the rock to break apart into small pieces. In high energy environments rocks break apart much faster than in more calm settings. For example, Granite rocks this means more Feldspar minerals in the sand because it wouldn't have had time to dissolve; the term for sand formed by weathering is epiclastic. Sand from rivers are collected either from the river itself or its flood plain, accounts for the majority of the sand used in the construction industry; because if this, many small rivers have been depleted, causing environmental concern and economic losses to adjacent land. The rate of sand mining in such areas outweighs the rate the sand can replenish, making it a non-renewable resource. Sand dunes are a consequence of wind deposition; the Sahara Desert is dry because of its geographic location and is known for its vast sand dunes. They exist here because little vegetation is able to grow and there's not a lot of water.
Over time, wind blow