1.
Greece
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Greece, officially the Hellenic Republic, historically also known as Hellas, is a country in southeastern Europe, with a population of approximately 11 million as of 2015. Athens is the capital and largest city, followed by Thessaloniki. Greece is strategically located at the crossroads of Europe, Asia, situated on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, the Republic of Macedonia and Bulgaria to the north, and Turkey to the northeast. Greece consists of nine regions, Macedonia, Central Greece, the Peloponnese, Thessaly, Epirus, the Aegean Islands, Thrace, Crete. The Aegean Sea lies to the east of the mainland, the Ionian Sea to the west, the Cretan Sea and the Mediterranean Sea to the south. Greece has the longest coastline on the Mediterranean Basin and the 11th longest coastline in the world at 13,676 km in length, featuring a vast number of islands, eighty percent of Greece is mountainous, with Mount Olympus being the highest peak at 2,918 metres. From the eighth century BC, the Greeks were organised into various independent city-states, known as polis, which spanned the entire Mediterranean region and the Black Sea. Greece was annexed by Rome in the second century BC, becoming a part of the Roman Empire and its successor. The Greek Orthodox Church also shaped modern Greek identity and transmitted Greek traditions to the wider Orthodox World, falling under Ottoman dominion in the mid-15th century, the modern nation state of Greece emerged in 1830 following a war of independence. Greeces rich historical legacy is reflected by its 18 UNESCO World Heritage Sites, among the most in Europe, Greece is a democratic and developed country with an advanced high-income economy, a high quality of life, and a very high standard of living. A founding member of the United Nations, Greece was the member to join the European Communities and has been part of the Eurozone since 2001. Greeces unique cultural heritage, large industry, prominent shipping sector. It is the largest economy in the Balkans, where it is an important regional investor, the names for the nation of Greece and the Greek people differ from the names used in other languages, locations and cultures. The earliest evidence of the presence of human ancestors in the southern Balkans, dated to 270,000 BC, is to be found in the Petralona cave, all three stages of the stone age are represented in Greece, for example in the Franchthi Cave. Neolithic settlements in Greece, dating from the 7th millennium BC, are the oldest in Europe by several centuries and these civilizations possessed writing, the Minoans writing in an undeciphered script known as Linear A, and the Mycenaeans in Linear B, an early form of Greek. The Mycenaeans gradually absorbed the Minoans, but collapsed violently around 1200 BC and this ushered in a period known as the Greek Dark Ages, from which written records are absent. The end of the Dark Ages is traditionally dated to 776 BC, the Iliad and the Odyssey, the foundational texts of Western literature, are believed to have been composed by Homer in the 7th or 8th centuries BC. With the end of the Dark Ages, there emerged various kingdoms and city-states across the Greek peninsula, in 508 BC, Cleisthenes instituted the worlds first democratic system of government in Athens
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Vehicle registration plates of Greece
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Greek vehicle registration plates are composed of three letters and four digits per plate. The letters represent the district that issues the plates while the numbers begin from 1000 to 9999, similar plates with digits beginning from 1 to 999 are issued for motorcycles which exceed 50 cc. With the exception of Athens and Thessaloniki, all districts are represented by the first 2 letters, the final letter in the sequence changes in Greek alphabetical order after 9,000 issued plates. For example, Patras plates are ΑΧΑ-1000, where ΑΧ represents the Achaia prefecture of which Patras is the capital, when ΑΧΑ-9999 is reached the plates turn to ΑΧΒ-1000 and this continues until ΑΧΧ is finished. Only the letters from the intersection between the Latin and Greek alphabets by glyph appearance are used, namely Α, Β, Ε, Ζ, Η, Ι, Κ, Μ, Ν, Ο, Ρ, Τ, Υ, Χ. This is because Greece is a party to the Vienna Convention on Road Traffic. The rule applies in a way in Russia, Ukraine, Belarus, Bosnia and Herzegovina. Combinations used for residents are L-NNNN and are limited. Until 2003, taxis used L-NNNN, the plate was aligned with the prefecture, when number plates were introduced to Greece, they were numbered and in the late 1950s the system was L-NNN and LL-NNN. The letters were Greek letters and Latin letters, respectively, in 1956, the system was NNNNNN. In 1972, they became lettered and the system was LL-NNNN while trucks used L-NNNN, in 1983, the system was LLL-NNNN and the first two letters are prefecture letters. In 2004, the euroband was added, the first 2 of 3 letters of a licence plate usually represent the prefecture where the car was registered. Π. — Disabled in war ΔΟΚ — Test plates ΔΣ — Corps Diplomatique or foreign delegation Ε. Α. or ΕΛ. ΑΣ. — Hellenic Police ΛΣ — Coast Guard ΞΑ — Foreign missions ΕΣ — Hellenic Army ΠΑ — Hellenic Air Force ΠΝ — Hellenic Navy ΠΣ — Fire Guard ΠΚ — President of the Government, i. e
3.
Piraeus
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Piraeus is a port city in the region of Attica, Greece. Piraeus is located within the Athens urban area,12 kilometres southwest from its city center, the municipality of Piraeus and several other suburban municipalities within the regional unit of Piraeus form the greater Piraeus area, with a total population of 448,997. Piraeus has a recorded history, dating to ancient Greece. During the Golden Age of Athens the Long Walls were constructed to connect Athens with Piraeus, the port of Piraeus is the chief port in Greece, the largest passenger port in Europe and the second largest in the world, servicing about 20 million passengers annually. With a throughput of 1.4 million TEUs, Piraeus is placed among the top ten ports in container traffic in Europe, the city hosted events in both the 1896 and 2004 Summer Olympics held in Athens. The University of Piraeus is one of the largest universities in Greece, Piraeus, which roughly means the place over the passage, has been inhabited since the 26th century BC. Consequently, it was called the Halipedon, meaning the salt field, through the centuries, the area was increasingly silted and flooding ceased, and thus by early classical times the land passage was made safe. In the late 6th century BC, the area caught attention due to its advantages, in 511 BC, the hill of Munichia was fortified by Hippias and four years later Piraeus became a deme of Attica by Cleisthenes. The Athenian fleet played a role in the battle of Salamis against the Persians in 480 BC. From then on Piraeus was permanently used as the navy base, the citys fortification was farther reinforced later by the construction of the Long Walls under Cimon and Pericles, with which Piraeus was connected to Athens. Meanwhile, Piraeus was rebuilt to the grid plan of architect Hippodamus of Miletus, known as the Hippodamian plan. As a result, Piraeus flourished and became a port of high security and great commercial activity, during the Peloponnesian War, Piraeus suffered its first setback. In the second year of the war, the first cases of the Athens plague were recorded in Piraeus, in 404 BC, the Spartan fleet under Lysander blockaded Piraeus and subsequently Athens surrendered to the Spartans, putting an end to the Delian League and the war itself. As a result, the tattered and unfortified port city was not able to compete with prosperous Rhodes, the destruction was completed in 395 AD by the Goths under Alaric I. Piraeus was led to a period of decline which lasted for fifteen centuries. During the Byzantine period the harbour of Piraeus was occasionally used for the Byzantine fleet and it was also called Porto Drako by Greeks, drako meaning not just dragon, but any monster. When Piraeus was taken by the Ottoman Empire in 1456, it known as Aslan Liman. The Piraeus Lion itself was looted in 1687 by Francesco Morosini during his expedition against Athens and was carried to the Venetian Arsenal, a copy of the lion statue is on display at the Archaeological Museum of Piraeus
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Peloponnese
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The Peloponnese or Peloponnesus is a peninsula and geographic region in southern Greece. It is separated from the part of the country by the Gulf of Corinth. During the late Middle Ages and the Ottoman era, the peninsula was known as the Morea, the peninsula is divided among three administrative regions, most belongs to the Peloponnese region, with smaller parts belonging to the West Greece and Attica regions. In 2016, Lonely Planet voted the Peloponnese the top spot of their Best in Europe list, the Peloponnese is a peninsula that covers an area of some 21,549.6 square kilometres and constitutes the southernmost part of mainland Greece. It has two connections with the rest of Greece, a natural one at the Isthmus of Corinth. The peninsula has an interior and deeply indented coasts. The Peloponnese possesses four south-pointing peninsulas, the Messenian, the Mani, the Cape Malea, mount Taygetus in the south is the highest mountain in the Peloponnese, at 2,407 metres. Οther important mountains include Cyllene in the northeast, Aroania in the north, Erymanthos and Panachaikon in the northwest, Mainalon in the center, the entire peninsula is earthquake prone and has been the site of many earthquakes in the past. The longest river is the Alfeios in the west, followed by the Evrotas in the south, extensive lowlands are found only in the west, with the exception of the Evrotas valley in the south and in the Argolid in the northeast. The Peloponnese is home to spectacular beaches, which are a major tourist draw. Two groups of islands lie off the Peloponnesian coast, the Argo-Saronic Islands to the east, the island of Kythera, off the Epidaurus Limera peninsula to the south of the Peloponnese, is considered to be part of the Ionian Islands. The island of Elafonissos used to be part of the peninsula but was separated following the quake of 365 AD. Since antiquity, and continuing to the present day, the Peloponnese has been divided into seven regions, Achaia, Corinthia, Argolid, Arcadia, Laconia, Messinia. Each of these regions is headed by a city, the largest city is Patras in Achaia, followed by Kalamata in Messinia. The peninsula has been inhabited since prehistoric times and its modern name derives from ancient Greek mythology, specifically the legend of the hero Pelops, who was said to have conquered the entire region. The name Peloponnesos means Island of Pelops, the Mycenaean civilization, mainland Greeces first major civilization, dominated the Peloponnese in the Bronze Age from its stronghold at Mycenae in the north-east of the peninsula. The Mycenean civilization collapsed suddenly at the end of the 2nd millennium BC, archeological research has found that many of its cities and palaces show signs of destruction. The subsequent period, known as the Greek Dark Ages, is marked by an absence of written records
5.
Ferry
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A ferry is a merchant vessel used to carry passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate regular return services, a passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water taxi. Ferries form a part of the transport systems of many waterside cities and islands. However, ship connections of much larger distances may also be called ferry services, the profession of the ferryman is embodied in Greek mythology in Charon, the boatman who transported souls across the River Styx to the Underworld. Speculation that a pair of oxen propelled a ship having a wheel can be found in 4th century Roman literature Anonymus De Rebus Bellicis. Though impractical, there is no reason why it could not work and such a ferry, see When Horses Walked on Water, Horse-Powered Ferries in Nineteenth-Century America. The Marine Services Company of Tanzania offers passenger and cargo services in three of the African Great Lakes viz, Lake Victoria, Lake Tanganyika and Lake Nyasa. It also operates one of the oldest ferries in the region, Ferries from Great Britain also sail to Belgium, Denmark, the Netherlands, Norway, Spain and Ireland. Some ferries carry mainly tourist traffic, but most also carry freight, in Britain, car-carrying ferries are sometimes referred to as RORO for the ease by which vehicles can board and leave. The busiest single ferry route is across the part of Øresund. Before the Øresund bridge was opened in July 2000, car and car & train ferries departed up to seven times every hour, in 2013, this has been reduced, but a car ferry still departs from each harbor every 15 minutes during daytime. The route is around 2.2 nautical miles and the crossing takes 22 minutes, today, all ferries on this route are constructed so that they do not need to turn around in the harbors. This also means that the ferries lack natural stems and sterns, due to the same circumstances, starboard and port-side are dynamic and depending of in what direction the ferry sails. Despite the short crossing, the ferries are equipped with restaurants, cafeteria, kiosks, large cruiseferries sail in the Baltic Sea between Finland, Åland, Sweden, Estonia, Latvia and Saint Petersburg, Russia and from Italy to Sardinia, Corsica, Spain and Greece. In many ways, these ferries are like cruise ships, also many smaller ferries operate on domestic routes in Finland, Sweden and Estonia. The south-west and southern parts of the Baltic Sea has several routes mainly for heavy traffic, on the longer of these routes, simple cabins are available. In Istanbul, ferries connect the European and Asian shores of Bosphorus, as well as Princes Islands, in 2014 İDO transported 47 million passengers, the largest ferry system in the world. Due to the numbers of freshwater lakes and length of shoreline in Canada
6.
Hydrofoil
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A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes, boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains speed, the lift the boats hull out of the water, decreasing drag. The hydrofoil usually consists of a wing like structure mounted on struts below the hull, as a hydrofoil equipped watercraft increases in speed, the hydrofoil elements below the hull develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides an increase in speed and fuel efficiency. Wider adoption of hydrofoils is prevented by the complexity of building and maintaining them. Hydrofoils are generally more expensive than conventional watercraft. However, the design is simple enough that there are many human-powered hydrofoil designs, amateur experimentation and development of the concept is popular. Since air and water are governed by similar fluid equations—albeit with different levels of viscosity, density, the foil shape moves smoothly through the water, deflecting the flow downward, which, following the Euler equations, exerts an upward force on the foil. This turning of the water creates higher pressure on the bottom of the foil and this pressure difference is accompanied by a velocity difference, via Bernoullis principle, so the resulting flowfield about the foil has a higher average velocity on one side than the other. When used as an element on a hydrofoil boat, this upward force lifts the body of the vessel, decreasing drag. The lifting force eventually balances with the weight of the craft, reaching a point where the no longer lifts out of the water. Hydrofoils of this type are known as surface-piercing since portions of the V-shape hydrofoils rise above the surface when foilborne. Some modern hydrofoils use fully submerged inverted T-shape foils, fully submerged hydrofoils are less subject to the effects of wave action, and, therefore, more stable at sea and more comfortable for crew and passengers. This type of configuration, however, is not self-stabilizing, the angle of attack on the hydrofoils must be adjusted continuously to changing conditions, a control process performed by sensors, a computer, and active surfaces. Italian inventor Enrico Forlanini began work on hydrofoils in 1898 and used a ladder foil system, Forlanini obtained patents in Britain and the United States for his ideas and designs. Between 1899 and 1901, British boat designer John Thornycroft worked on a series of models with a stepped hull, in 1909 his company built the full scale 22-foot long boat, Miranda III. Driven by a 60 hp engine, it rode on a bowfoil, the subsequent Miranda IV was credited with a speed of 35 kn
7.
Hydra (island)
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Hydra is one of the Saronic Islands of Greece, located in the Aegean Sea between the Saronic Gulf and the Argolic Gulf. It is separated from the Peloponnese by a strip of water. In ancient times, the island was known as Hydrea, a reference to the springs on the island. The municipality of Hydra consists of the islands Hydra, Dokos, the province of Hydra was one of the provinces of the Piraeus Prefecture. Its territory corresponded with that of the current municipality, there is one main town, known simply as Hydra port. It consists of a harbor, around which is centered a strand of restaurants, shops, markets. Steep stone streets lead up and outward from the harbor area, most of the local residences, as well as the hostelries on the island, are located on these streets. Other small villages or hamlets on the island include Mandraki, Kamini, Vlychos, Palamidas, Episkopi, Hydra depends on tourism, and Athenians account for a sizable segment of its visitors. High-speed hydrofoils and catamarans from Piraeus, some 37 nautical miles away, serve Hydra, there is a passenger ferry service providing an alternative to Hydrofoils that runs from Hydra Harbor to Metochi on the Peloponnese coast. Many Athenians drive to Metochi, leave their car in the car park. Rubbish trucks are the motor vehicles on the island, since by law, cars. Horses, mules and donkeys, and water taxis provide public transportation, the inhabited area, however, is so compact that most people walk everywhere. Hydra benefits from numerous bays and natural harbors, and has a maritime culture. The island is a popular yachting destination and is the home of the Kamini Yacht Club, in 2007, a National Geographic Traveler panel of 522 experts rated Hydra the highest of any Greek island as a unique destination preserving its integrity of place. The Tsamadou mansion on the side of the harbor as one enters is now a Maritime Academy. The Tombazi mansion is now part of the School of Fine Arts, the mansions of Lazarus and George Kountouriotis, Boudouri, Kriezi, Voulgari, Sahini, and Miaouli all contain collections of 18th-century island furniture. The descendants of Lazarus Kountouriotis donated his mansion to the Historic-Ethnologic Institute of Greece, today, it operates as an extension branch of the National Museum of History. There are numerous churches and six Orthodox monasteries on the island, two particularly noteworthy monasteries are Profitis Ilias, founded in the 10th century, and Ayia Efpraxia
8.
Mesozoic
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The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. This Era is also called from a paleobotanist view the Age of Conifers, Mesozoic means middle life, deriving from the Greek prefix meso-/μεσο- for between and zōon/ζῷον meaning animal or living being. It is one of three eras of the Phanerozoic Eon, preceded by the Paleozoic and succeeded by the Cenozoic. The era is subdivided into three periods, the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs. The Mesozoic was a time of significant tectonic, climate and evolutionary activity, the era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would eventually move into their current positions. The climate of the Mesozoic was varied, alternating between warming and cooling periods, overall, however, the Earth was hotter than it is today. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs, the first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg —until the Cenozoic. Following the Paleozoic, the Mesozoic extended roughly 186 million years and this time frame is separated into three geologic periods. It is also known as the Great Dying because it is considered the largest mass extinction in the Earths history, the upper boundary of the Mesozoic is set at the Cretaceous–Paleogene extinction event, which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula. Towards the Late Cretaceous large volcanic eruptions are believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of the non-avian dinosaurs, the Triassic ranges roughly from 252 million to 201 million years ago. The Triassic is a time in Earths history bracketed between the Permian Extinction and the Triassic–Jurassic extinction event, two of the big five, and precedes the Jurassic Period and it has three major epochs, the Early Triassic, the Middle Triassic and the Late Triassic. The Early Triassic was between about 252 million to 247 million years ago and was dominated by deserts as Pangaea had not yet broken up, thus the interior was nothing, the Earth had just witnessed a massive die-off in which 95% of all life became extinct. The most common life on earth were Lystrosaurus, labyrinthodonts. Temnospondyls evolved during this time and would be the dominant predator for much of the Triassic, the Middle Triassic spans roughly from 247 million to 237 million years ago. The Middle Triassic featured the beginnings of the breakup of Pangaea, the ecosystem had recovered from the devastation that was the Great Dying. Algae, sponge, corals, and crustaceans all had recovered, new aquatic reptiles evolved, such as ichthyosaurs and nothosaurs. Meanwhile, on land, pine forests flourished, as did groups of insects like mosquitoes, the first ancient crocodilians evolved, which sparked competition with the large amphibians that had since ruled the freshwater world
9.
Sedimentary rock
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Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
10.
Limestone
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Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and 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 commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, 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, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the 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 building process, limestone recrystallizes into marble
11.
Sandstone
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Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
12.
Ophiolite
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An ophiolite is a section of the Earths oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. Ophio is Greek for snake, and lite means stone from the Greek lithos, the term was little-used in other areas until the late 1950s to early 1960s, with the recognition that this assemblage provided an analog for oceanic crust and the process of seafloor spreading. Moores and Vine concluded that the dike complex at Troodos could form only by a process similar to the seafloor spreading proposed by Vine. Thus, it widely accepted that ophiolites represent oceanic crust that had been emplaced on land. This insight was one of the pillars of plate tectonics, and ophiolites have always played a central role in plate tectonic theory. The stratigraphic sequence observed in ophiolites corresponds to the processes at mid-oceanic ridges, Sediments, muds. Extrusive sequence, basaltic pillow lavas show magma/seawater contact, sheeted dike complex, vertical, parallel dikes that fed lavas above. High level intrusives, isotropic gabbro, indicative of fractionated magma chamber, layered gabbro, resulting from settling out of minerals from a magma chamber. Cumulate peridotite, dunite-rich layers of minerals that settled out from a magma chamber, the Penrose field conference on ophiolites in 1972 redefined the term ophiolite to include only the igneous rocks listed above, excluding the sediments formed independently of the crust they sit on. Oceanic crust has a layered velocity structure that implies a layered rock series similar to that listed above, in detail there are problems, with many ophiolites exhibiting thinner accumulations of igneous rock than are inferred for oceanic crust. Another problem relating oceanic crust and ophiolites is that the thick layer of ophiolites calls for large magma chambers beneath mid-ocean ridges. Seismic sounding of mid-ocean ridges has revealed only a few magma chambers beneath ridges, a few deep drill holes into oceanic crust have intercepted gabbro, but it is not layered like ophiolite gabbro. For example, plagioclase, pyroxenes, and olivine in the dikes and lavas will alter to albite, chlorite. Thus there is reason to believe that ophiolites are indeed oceanic mantle and crust, however and these chemical differences extend to a range of trace elements as well. The crystallization order of feldspar and pyroxene in the gabbros is reversed, indeed, there is increasing evidence that most ophiolites are generated when subduction begins and thus represent fragments of fore-arc lithosphere. This led to introduction of the term supra-subduction zone ophiolite in the 1980s to acknowledge that some ophiolites are more related to island arcs than ocean ridges. A fore-arc setting for most ophiolites also solves the problem of how oceanic lithosphere can be emplaced on top of continental crust. Most ophiolites can be divided one of two groups, Tethyan and Cordilleran
"Poros". Encyclopædia Britannica (11th ed.). 1911.
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