1.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
2.
Pacific Ocean
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The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan, trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese also reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands. The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions also discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain also sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
3.
Tuamotus
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Its major islands are Anaa, Fakarava, Hao and Makemo. The Tuamotu islands were settled by Polynesians, so Tuamotuans share a common culture. French Polynesia is an island group designated as an overseas country of France. The Tuamotus combine with the Gambier Islands to form the Îles Tuamotu-Gambier which is one of the five divisions of French Polynesia. The Tuamotus are grouped into sixteen communes, Anaa, Arutua, Fakarava, Fangatau, Hao, Hikueru, Makemo, Manihi, Napuka, Nukutavake, Puka Puka, Rangiroa, Reao, Takaroa, Tatakoto, and Tureia. The communes on Tuamotu are part of two different electoral districts represented in the Assembly of French Polynesia, the other five communes in western Tuamotu – Arutua, Fakarava, Manihi, Rangiroa, and Takaroa – form the Îles Tuamotu Ouest electoral district. At the 2007 census, the Tuamotus had a population of 18,317 inhabitants, of these,769 inhabitants live in a 215-nautical-mile radius around Mururoa and Fangataufa, the sites of former French nuclear tests. The common language spoken in the Tuamotus is Tuamotuan, except in Puka-Puka which uses the Marquesan language, the islands economy is predominantly composed of subsistence agriculture. The most important sources of income are the cultivation of black pearls. Tourism-related income remains meager, especially by comparison to the industry of the neighboring Society Islands. A modest tourism infrastructure is found on the atolls of Rangiroa, despite the vast spread of the archipelago, it covers a total land area of only about 885 km2. The climate is tropical, without pronounced seasons. The annual average temperature is a relatively continuous 26 °C, water sources such as lakes or rivers are absent, leaving catchments of rain as the only source of fresh water. The annual average rainfall is 1400 mm, rainfall is not markedly different throughout the year, although it is lowest during the months of September and November. Geological stability of the archipelago is high, as it was created by the weakly active Easter Fracture Zone, no volcanic eruptions have been recorded historically. The sparse soil of the coral islands does not permit a diverse vegetation, the coconut palm, which forms the basis for copra production, is of special economic importance. On a few islands, vanilla is also cultivated, agriculture is generally otherwise limited to simple subsistence. Fruit and vegetable staples include yams, taro, and breadfruit, pandanus leaves are traditionally woven together as roof thatch, as well as for other items, such as mats and hats
4.
French Polynesia
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It is composed of 118 geographically dispersed islands and atolls stretching over an expanse of more than 2,000 kilometres in the South Pacific Ocean. Its total land area is 4,167 square kilometres, among its 118 islands and atolls,67 are inhabited. Tahiti, which is located within the Society Islands, is the most populous island and it has more than 68% of the population of the islands in 2012. Although not a part of its territory, Clipperton Island was administered from French Polynesia until 2007. Following the Great Polynesian Migration, European explorers visited the islands of French Polynesia on several occasions, traders and whaling ships also visited. In 1842, the French took over the islands and established a French protectorate they called Etablissements des français en Océanie, in 1946, the EFOs became an overseas territory under the constitution of the French Fourth Republic, and Polynesians were granted the right to vote through citizenship. In 1957, the EFOs were renamed French Polynesia, French Polynesia as we know it today was one of the last places on Earth to be settled by humans. Scientists believe the Great Polynesian Migration happened around 1500 BC as Austronesian people went on a journey using celestial navigation to find islands in the South Pacific Ocean, the first islands of French Polynesia to be settled were the Marquesas Islands in about 200 BC. The Polynesians later ventured southwest and discovered the Society Islands around AD300, European encounters began in 1521 when Portuguese explorer Ferdinand Magellan, sailing at the service of the Spanish Crown, sighted Puka-Puka in the Tuāmotu-Gambier Archipelago. Over a century later, British explorer Samuel Wallis visited Tahiti in 1767, French explorer Louis Antoine de Bougainville also visited Tahiti in 1768, while British explorer James Cook arrived in 1769. A short-lived Spanish settlement was created in 1774, and for a time some maps bore the name Isla de Amat after Viceroy Amat, in 1772, Dutchman Jakob Roggeveen came across Bora Bora in the Society Islands. Christian missions began with Spanish priests who stayed in Tahiti for a year, protestants from the London Missionary Society settled permanently in Polynesia in 1797. King Pōmare II of Tahiti was forced to flee to Moorea in 1803, he, French Catholic missionaries arrived on Tahiti in 1834, their expulsion in 1836 caused France to send a gunboat in 1838. In 1842, Tahiti and Tahuata were declared a French protectorate, the capital of Papeetē was founded in 1843. In 1880, France annexed Tahiti, changing the status from that of a protectorate to that of a colony, the island groups were not officially united until the establishment of the French protectorate in 1889. In the 1880s, France claimed the Tuamotu Archipelago, which belonged to the Pōmare Dynasty. Having declared a protectorate over Tahuata in 1842, the French regarded the entire Marquesas Islands as French, in 1885, France appointed a governor and established a general council, thus giving it the proper administration for a colony. The islands of Rimatara and Rūrutu unsuccessfully lobbied for British protection in 1888, postage stamps were first issued in the colony in 1892
5.
Coral
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Corals are marine invertebrates in the class Anthozoa of phylum Cnidaria. They typically live in colonies of many identical individual polyps. The group includes the important reef builders that inhabit tropical oceans, a coral group is a colony of myriad genetically identical polyps. Each polyp is an animal typically only a few millimeters in diameter. A set of tentacles surround a central mouth opening, an exoskeleton is excreted near the base. Over many generations, the colony creates a large skeleton that is characteristic of the species. Individual heads grow by reproduction of polyps. Corals also breed sexually by spawning, polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon and these are commonly known as zooxanthellae and the corals that contain them are zooxanthellate corals. Such corals require sunlight and grow in clear, shallow water, other corals do not rely on zooxanthellae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3,000 metres. Some have been found on the Darwin Mounds, north-west of Cape Wrath, Corals have also been found as far north as off the coast of Washington State and the Aleutian Islands. In his Scala Naturae, Aristotle classified corals as zoophyta, animals that had characteristics of plants and were therefore hypothetically in between animals and plants, the Persian polymath Al-Biruni classified sponges and corals as animals, arguing that they respond to touch. The phylogeny of Anthozoans is not clearly understood and a number of different models have been proposed, within the Hexacorallia, the sea anemones, coral anemones and stony corals may constitute a monophyletic grouping united by their eight-fold symmetry and cnidocyte trait. The Octocorallia appears to be monophyletic, and primitive members of this group may have been stolonate, the cladogram presented here comes from a 2014 study by Stampar et al. which was based on the divergence of mitochondrial DNA within the group and on nuclear markers. Corals are classified in the class Anthozoa of the phylum Cnidaria and they are divided into three subclasses, Hexacorallia, Octocorallia, and Ceriantharia. The Hexacorallia include the stony corals, the sea anemones and the zoanthids and these groups have polyps that generally have 6-fold symmetry. The Octocorallia include blue coral, soft corals, sea pens and these groups have polyps with 8-fold symmetry, each polyp having eight tentacles and eight mesenteries. Fire corals are not true corals, being in the order Anthomedusa of the class Hydrozoa, Corals are sessile animals in the class Anthozoa and differ from most other cnidarians in not having a medusa stage in their life cycle. The body unit of the animal is a polyp, most corals are colonial, the initial polyp budding to produce another and the colony gradually developing from this small start
6.
Atoll
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An atoll, sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands/cays on the rim, the coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the crater or caldera while the higher rim remains above water or at shallow depths that permit the coral to grow. For the atoll to persist, continued erosion or subsidence must be at a slow enough to permit reef growth upwards and outwards to replace the lost height. The word atoll comes from the Dhivehi word atholhu, meaning an administrative subdivision, the distribution of atolls around the globe is instructive, most of the worlds atolls are in the Pacific Ocean and Indian Ocean. The Atlantic Ocean has no large groups of atolls, other than eight atolls east of Nicaragua that belong to the Colombian department of San Andres and Providencia in the Caribbean. Reef-building corals will thrive only in tropical and subtropical waters of oceans and seas. The northernmost atoll of the world is Kure Atoll at 28°24 N, the southernmost atolls of the world are Elizabeth Reef at 29°58 S, and nearby Middleton Reef at 29°29 S, in the Tasman Sea, both of which are part of the Coral Sea Islands Territory. The next southerly atoll is Ducie Island in the Pitcairn Islands Group, at this latitude coral reefs would not develop without the warming waters of the Gulf Stream. However, Bermuda is termed a pseudo-atoll because its general form, while there is no atoll directly on the equator, the closest atoll to the Equator is Aranuka of Kiribati, with its southern tip just 12 km north of the equator. In most cases, the area of an atoll is very small in comparison to the total area. Atoll islands are low lying, with their elevations less than 5 meters, measured by total area, Lifou is the largest raised coral atoll of the world, followed by Rennell Island. More sources however list as the largest atoll in the world in terms of land area Kiritimati, the remains of an ancient atoll as a hill in a limestone area is called a reef knoll. The second largest atoll by dry land area is Aldabra with 155 km², the largest atoll in terms of island numbers is Huvadhu Atoll in the south of the Maldives with 255 islands. In 1842, Charles Darwin explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a voyage aboard the HMS Beagle from 1831 to 1836. In time, subsidence carries the old volcano below the ocean surface, at this point, the island has become an atoll. Atolls are the product of the growth of marine organisms. Volcanic islands located beyond the water temperature requirements of hermatypic organisms become seamounts as they subside and are eroded away at the surface
7.
Tahiti
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Tahiti is the largest island in the Windward group of French Polynesia, this overseas collectivity of the French Republic is sometimes referred to as a French overseas country. The island was formed from volcanic activity and is high and mountainous with surrounding coral reefs, the population is 183,645 inhabitants, making it the most populous island of French Polynesia and accounting for 68.5 percent of its total population. Tahiti is the economic, cultural and political centre of French Polynesia, the capital, Papeete, is located on the northwest coast with the only international airport in the region, Faaā International Airport, situated 5 km from the town centre. Tahiti was originally settled by Polynesians between 300 and 800 CE and they represent about 70 percent of the islands population with the rest made up of Europeans, Chinese and those of mixed heritage. The island was part of the Kingdom of Tahiti until its annexation by France in 1880, when it was proclaimed a colony of France, French is the only official language although the Tahitian language is widely spoken. Tahiti is the highest and largest island in French Polynesia lying close to Moorea island and it is located 4,400 kilometres south of Hawaii,7,900 km from Chile and 5,700 km from Australia. The island is 45 km across at its widest point and covers an area of 1,045 km2, the highest peak is Mont Orohena. Mount Roonui, or Mount Ronui in the southeast rises to 1,332 m, the island consists of two roughly round portions centred on volcanic mountains and connected by a short isthmus named after the small town of Taravao, situated there. The northwestern portion is known as Tahiti Nui, while the much smaller portion is known as Tahiti Iti or Taiarapū. Tahiti Nui is heavily populated along the coast, especially around the capital, the interior of Tahiti Nui is almost entirely uninhabited. Tahiti Iti has remained isolated, as its half is accessible only to those travelling by boat or on foot. The rest of the island is encircled by a road which cuts between the mountains and the sea. A scenic and winding road climbs past dairy farms and citrus groves with panoramic views. Tahitis landscape features lush rainforests and many rivers and waterfalls, including the Papenoo River on the side. November to April is the wet season, the wettest month of which is January with 13.2 in of rain in Papeetē, August is the driest with 1.9 inches. The average temperature ranges between 21 and 31 °C with little seasonal variation, the lowest and highest temperatures recorded in Papeete are 16 and 34 °C, respectively. The first Tahitians arrived from Southeast Asia in about 200 BCE and this hypothesis of an emigration from Southeast Asia is supported by a number of linguistic, biological and archaeological proofs. For example, the languages of Fiji and Polynesia all belong to the same Oceanic sub-group, Fijian-Polynesian, in 1769, for instance, James Cook mentions a great traditional ship in Tahiti that was 33 m long, and could be propelled by sail or paddles
8.
Tessellation
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A tessellation of a flat surface is the tiling of a plane using one or more geometric shapes, called tiles, with no overlaps and no gaps. In mathematics, tessellations can be generalized to higher dimensions and a variety of geometries, a periodic tiling has a repeating pattern. The patterns formed by periodic tilings can be categorized into 17 wallpaper groups, a tiling that lacks a repeating pattern is called non-periodic. An aperiodic tiling uses a set of tile shapes that cannot form a repeating pattern. In the geometry of higher dimensions, a space-filling or honeycomb is called a tessellation of space. A real physical tessellation is a made of materials such as cemented ceramic squares or hexagons. Such tilings may be decorative patterns, or may have such as providing durable and water-resistant pavement. Historically, tessellations were used in Ancient Rome and in Islamic art such as in the decorative geometric tiling of the Alhambra palace, in the twentieth century, the work of M. C. Escher often made use of tessellations, both in ordinary Euclidean geometry and in geometry, for artistic effect. Tessellations are sometimes employed for decorative effect in quilting, Tessellations form a class of patterns in nature, for example in the arrays of hexagonal cells found in honeycombs. Tessellations were used by the Sumerians in building wall decorations formed by patterns of clay tiles, decorative mosaic tilings made of small squared blocks called tesserae were widely employed in classical antiquity, sometimes displaying geometric patterns. In 1619 Johannes Kepler made a documented study of tessellations. He wrote about regular and semiregular tessellations in his Harmonices Mundi, he was possibly the first to explore and to explain the structures of honeycomb. Some two hundred years later in 1891, the Russian crystallographer Yevgraf Fyodorov proved that every periodic tiling of the features one of seventeen different groups of isometries. Fyodorovs work marked the beginning of the mathematical study of tessellations. Other prominent contributors include Shubnikov and Belov, and Heinrich Heesch, in Latin, tessella is a small cubical piece of clay, stone or glass used to make mosaics. The word tessella means small square and it corresponds to the everyday term tiling, which refers to applications of tessellations, often made of glazed clay. Tessellation or tiling in two dimensions is a topic in geometry that studies how shapes, known as tiles, can be arranged to fill a plane without any gaps, according to a given set of rules
9.
Nauru
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Nauru, officially the Republic of Nauru and formerly known as Pleasant Island, is an island country in Micronesia in the Central Pacific. Its nearest neighbour is Banaba Island in Kiribati,300 kilometres to the east and it further lies northwest of Tuvalu, north of the Solomon Islands, east-northeast of Papua New Guinea, southeast of the Federated States of Micronesia and south of the Marshall Islands. With 10,084 residents in a 21-square-kilometre area, Nauru is the smallest state in the South Pacific and third smallest state by area in the world, behind only Vatican City and Monaco. Settled by native peoples from Micronesia and Polynesia, Nauru was annexed and claimed as a colony by the German Empire in the late 19th century, after World War I, Nauru became a League of Nations mandate administered by Australia, New Zealand and the United Kingdom. During World War II, Nauru was occupied by Japanese troops, after the war ended, the country entered into UN trusteeship. Nauru gained its independence in 1968, Nauru is a phosphate rock island with rich deposits near the surface, which allowed easy strip mining operations. It has some remaining phosphate resources which, as of 2011, are not economically viable for extraction, Nauru boasted the highest per-capita income enjoyed by any sovereign state in the world during the late 1960s and early 1970s. When the phosphate reserves were exhausted, and the environment had been seriously harmed by mining. To earn income, Nauru briefly became a tax haven and illegal money laundering centre, from 2001 to 2008, and again from 2012, it accepted aid from the Australian Government in exchange for hosting the Nauru detention centre. As a result of dependence on Australia, many sources have identified Nauru as a client state of Australia. Nauru was first inhabited by Micronesians and Polynesians at least 3,000 years ago, there were traditionally 12 clans or tribes on Nauru, which are represented in the 12-pointed star on the countrys flag. Traditionally, Nauruans traced their descent matrilineally, inhabitants practised aquaculture, they caught juvenile ibija fish, acclimatised them to fresh water, and raised them in the Buada Lagoon, providing a reliable source of food. The other locally grown components of their diet included coconuts and pandanus fruit, the name Nauru may derive from the Nauruan word Anáoero, which means I go to the beach. The British sea captain John Fearn, a hunter, became the first Westerner to visit Nauru in 1798. From around 1830, Nauruans had contact with Europeans from whaling ships, around this time, deserters from European ships began to live on the island. The islanders traded food for alcoholic palm wine and firearms, the firearms were used during the 10-year Nauruan Tribal War that began in 1878. After an agreement with Great Britain, Nauru was annexed by Germany in 1888, the arrival of the Germans ended the civil war, and kings were established as rulers of the island. The most widely known of these was King Auweyida, christian missionaries from the Gilbert Islands arrived in 1888
10.
Concrete
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Concrete is a composite material composed of coarse aggregate bonded together with a fluid cement that hardens over time. Most concretes used are lime-based concretes such as Portland cement concrete or concretes made with other hydraulic cements, when aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a matrix that binds the materials together into a durable stone-like material that has many uses. Often, additives are included in the mixture to improve the properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials embedded to provide tensile strength, famous concrete structures include the Hoover Dam, the Panama Canal, and the Roman Pantheon. The earliest large-scale users of technology were the ancient Romans. The Colosseum in Rome was built largely of concrete, and the dome of the Pantheon is the worlds largest unreinforced concrete dome. Today, large concrete structures are made with reinforced concrete. After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century, today, concrete is the most widely used man-made material. The word concrete comes from the Latin word concretus, the passive participle of concrescere, from con-. Perhaps the earliest known occurrence of cement was twelve years ago. A deposit of cement was formed after an occurrence of oil shale located adjacent to a bed of limestone burned due to natural causes and these ancient deposits were investigated in the 1960s and 1970s. On a human timescale, small usages of concrete go back for thousands of years and they discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of houses, concrete floors. The cisterns were kept secret and were one of the reasons the Nabataea were able to thrive in the desert, some of these structures survive to this day. In the Ancient Egyptian and later Roman eras, it was re-discovered that adding volcanic ash to the mix allowed it to set underwater, similarly, the Romans knew that adding horse hair made concrete less liable to crack while it hardened, and adding blood made it more frost-resistant. Crystallization of strätlingite and the introduction of pyroclastic clays creates further fracture resistance, german archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400–1200 BC. Lime mortars were used in Greece, Crete, and Cyprus in 800 BC, the Assyrian Jerwan Aqueduct made use of waterproof concrete
11.
Levee
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A levee, dike, dyke, embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines, the word levee, from the French word levée, is used in American English. It originated in New Orleans a few years after the founding in 1718 and was later adopted by English speakers. The name derives from the trait of the ridges being raised higher than both the channel and the surrounding floodplains. The modern word dike or dyke most likely derives from the Dutch word dijk, the 126 kilometres long Westfriese Omringdijk was completed by 1250, and was formed by connecting existing older dikes. The Roman chronicler Tacitus even mentions that the rebellious Batavi pierced dikes to flood their land, the word dijk originally indicated both the trench and the bank. It is closely related to the English verb to dig, in Anglo-Saxon, the word dic already existed and was pronounced as dick in northern England and as ditch in the south. Similar to Dutch, the English origins of the lie in digging a trench. This practice has meant that the name may be given to either the excavation or the bank, thus Offas Dyke is a combined structure and Car Dyke is a trench though it once had raised banks as well. In the midlands and north of England, and in the United States, a dike is what a ditch is in the south, a property boundary marker or small drainage channel. Where it carries a stream, it may be called a dike as in Rippingale Running Dike. The Weir Dike is a dike in Bourne North Fen, near Twenty and alongside the River Glen. In the Norfolk and Suffolk Broads, a dyke may be a ditch or a narrow artificial channel off a river or broad for access or mooring, some longer dykes being named. In parts of Britain, particularly Scotland, a dyke may be a field wall, Levees can be mainly found along the sea, where dunes are not strong enough, along rivers for protection against high-floods, along lakes or along polders. Furthermore, levees have been built for the purpose of empoldering, the latter can be a controlled inundation by the military or a measure to prevent inundation of a larger area surrounded by levees. Levees have also built as field boundaries and as military defences. More on this type of levee can be found in the article on dry-stone walls, Levees can be permanent earthworks or emergency constructions built hastily in a flood emergency. When such a bank is added on top of an existing levee it is known as a cradge
12.
Reef
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A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Reefs may be up to 261 feet below the surface, artificial reefs such as shipwrecks are sometimes created to enhance physical complexity on generally featureless sand bottoms in order to attract a diverse assemblage of organisms, especially fish. There is a variety of reef types, including oyster reefs. These biotic reef types take on additional names depending upon how the reef lies in relation to the land, Reef types include fringing reef, barrier reefs, as well as atolls. A fringing reef is a reef that is attached to an island, a barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a reef with no land present. The reef front is a high energy locale whereas the internal lagoon will be at an energy with fine grained sediments. One useful definition distinguishes reefs from mounds as follows, reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind, corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework, mounds are built by microorganisms or by organisms that dont grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria, excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake of Utah, and in Shark Bay, Western Australia. Cyanobacteria do not have skeletons and individuals are microscopic, cyanobacteria encourage the precipitation or accumulation of calcium carbonate and can produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, bryozoans and crinoids, common contributors to marine sediments during the Mississippian, produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate, however, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief. The Proterozoic Belt Supergroup contains evidence of microbial mat and dome structures similar to stromatolite reef complexes. Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide information about the location in Earths history. Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other groups, such as calcifying algae, especially members of the red algae Rhodophyta
