Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material, a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves, it conveys water and nutrients between the leaves, other growing tissues, the roots. Wood may refer to other plant materials with comparable properties, to material engineered from wood, or wood chips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons and paper. More it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
As of 2005, the growing stock of forests worldwide was about 434 billion cubic meters, 47% of, commercial. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991 3.5 billion cubic meters of wood were harvested. Dominant uses were for building construction. A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood 395 to 400 million years ago. Wood can be dated by carbon dating and in some species by dendrochronology to determine when a wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses, weapons, packaging and paper. Known constructions using wood date back ten thousand years. Buildings like the European Neolithic long house were made of wood. Recent use of wood has been enhanced by the addition of bronze into construction; the year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut.
Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, roots. This process is known as secondary growth; these cells go on to form thickened secondary cell walls, composed of cellulose and lignin. Where the differences between the four seasons are distinct, e.g. New Zealand, growth can occur in a discrete annual or seasonal pattern, leading to growth rings. If the distinctiveness between seasons is annual, these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will be deformed as the plant overgrows the scar. If there are differences within a growth ring the part of a growth ring nearest the center of the tree, formed early in the growing season when growth is rapid, is composed of wider elements.
It is lighter in color than that near the outer portion of the ring, is known as earlywood or springwood. The outer portion formed in the season is known as the latewood or summerwood. However, there are major differences, depending on the kind of wood; as a tree grows, lower branches die, their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base, can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood reducing the local strength and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a circular "solid" piece of wood around which the grain of the rest of the wood "flows". Within a knot, the direction of the wood is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a dormant bud.
A knot is conical in shape with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud. In grading lumber and structural timber, knots are classified according to their form, size and the firmness with which they are held in place; this firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow. Knots materially affect cracking and warping, ease in working, cleavability of timber, they are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression; the extent to which knots affect the strength of a beam depends upon their position, size and condition. A knot on the upper side is compressed. If there is a season check
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
Potash is some of various mined and manufactured salts that contain potassium in water-soluble form. The name derives from pot ash, which refers to plant ashes soaked in water in a pot, the primary means of manufacturing the product before the industrial era; the word potassium is derived from potash. Potash is produced worldwide at amounts exceeding 90 million tonnes per year for use in manufacturing. Various types of fertilizer-potash constitute the single largest industrial use of the element potassium in the world. Potassium was first derived in 1807 by electrolysis of caustic potash. Potash refers to potassium compounds and potassium-bearing materials, the most common being potassium chloride; the term potash comes from the Middle Dutch word potaschen. The old method of making potassium carbonate was by collecting or producing wood ash, leaching the ashes and evaporating the resulting solution in large iron pots, leaving a white residue called pot ash. 10% by weight of common wood ash can be recovered as pot ash.
Potash became the term applied to occurring potassium salts and the commercial product derived from them. The following table lists a number of potassium compounds which use the word potash in their traditional names: All commercial potash deposits come from evaporite deposits and are buried deep below the earth's surface. Potash ores are rich in potassium chloride, sodium chloride and other salts and clays, are obtained by conventional shaft mining with the extracted ore ground into a powder. Other methods include dissolution evaporation methods from brines. In the evaporation method, hot water is injected into the potash, dissolved and pumped to the surface where it is concentrated by solar induced evaporation. Amine reagents are added to either the mined or evaporated solutions; the amine coats the KCl but not NaCl. Air bubbles cling to the amine + KCl and float it to the surface while the NaCl and clay sink to the bottom; the surface is skimmed for the amine + KCl, dried and packaged for use as a K rich fertilizer—KCl dissolves in water and is available for plant nutrition.
Potash deposits can be found all over the world. At present, deposits are being mined in Canada, China, Israel, Chile, the United States, Spain, the United Kingdom and Brazil, with the most significant deposits present in Saskatchewan, Canada. Excessive respiratory disease has been a concern for potash miners throughout history due to environmental hazards, such as radon and asbestos. Potash miners are liable to develop silicosis. Based on a study done between 1977 and 1987 cardiovascular disease among potash workers, the overall mortality rates were low, but a noticeable difference in above ground workers was documented. Potash has been used in bleaching textiles, making glass, making soap, since about AD 500. Potash was principally obtained by leaching the ashes of sea plants. Beginning in the 14th century potash was mined in Ethiopia. One of the world's largest deposits, 140 to 150 million tons, is located in the Tigray's Dallol area. Potash was one of the most important industrial chemicals.
It was refined from the ashes of broadleaved trees and produced in the forested areas of Europe and North America. The first U. S. patent of any kind was issued in 1790 to Samuel Hopkins for an improvement "in the making of Pot ash and Pearl ash by a new Apparatus and Process". Pearl ash was a purer quality made by calcination of potash in kiln. Potash pits were once used in England to produce potash, used in making soap for the preparation of wool for yarn production; as early as 1767, potash from wood ashes was exported from Canada, exports of potash and pearl ash reached 43,958 barrels in 1865. There were 519 asheries in operation in 1871; the industry declined in the late 19th century when large-scale production of potash from mineral salts was established in Germany. In 1943, potash was discovered in Canada, in the process of drilling for oil. Active exploration began in 1951. In 1958, the Potash Company of America became the first potash producer in Canada with the commissioning of an underground potash mine at Patience Lake.
The underground mine was flooded in 1987 and was reactivated for commercial production as a solution mine in 1989. In the late 18th and early 19th centuries, potash production provided settlers in North America a way to obtain badly needed cash and credit as they cleared wooded land for crops. To make full use of their land, settlers needed to dispose of excess wood; the easiest way to accomplish this was to burn any wood not needed for construction. Ashes from hardwood trees could be used to make lye, which could either be used to make soap or boiled down to produce valuable potash. Hardwood could generate ashes at the rate of 60 to 100 bushels per acre. In 1790, ashes could be sold for $3.25 to $6.25 per acre in rural New York State – nearly the same rate as hiring a laborer to clear the same area. Potash making became a major industry in British North America. Great Britain was always the most important market; the American potash industry followed the woodsman's ax across the country. After about 1820, New York replaced New England as the most important source.
Potash production was always
Brittany is a cultural region in the northwest of France, covering the western part of what was known as Armorica during the period of Roman occupation. It became an independent kingdom and a duchy before being united with the Kingdom of France in 1532 as a province governed as if it were a separate nation under the crown. Brittany has been referred to as Less, Lesser or Little Britain, it is bordered by the English Channel to the north, the Celtic Sea and the Atlantic Ocean to the west, the Bay of Biscay to the south. Its land area is 34,023 km². Brittany is the site of some of the world's oldest standing architecture, home to the Barnenez, the Tumulus Saint-Michel and others, which date to the early 5th millennium BC. Today, the historical province of Brittany is split among five French departments: Finistère in the west, Côtes-d'Armor in the north, Ille-et-Vilaine in the north east, Loire-Atlantique in the south east and Morbihan in the south on the Bay of Biscay. Since reorganisation in 1956, the modern administrative region of Brittany comprises only four of the five Breton departments, or 80% of historical Brittany.
The remaining area of old Brittany, the Loire-Atlantique department around Nantes, now forms part of the Pays de la Loire region. At the 2010 census, the population of historic Brittany was estimated to be 4,475,295. Of these, 71 % lived in the region of Brittany. In 2012, the largest metropolitan areas were Nantes and Brest. Brittany is the traditional homeland of the Breton people and is recognised by the Celtic League as one of the six Celtic nations, retaining a distinct cultural identity that reflects its history. A nationalist movement seeks greater autonomy within the French Republic; the word Brittany, along with its French and Gallo equivalents Bretagne and Bertaèyn, derive from the Latin Britannia, which means "Britons' land". This word had been used by the Romans since the 1st century to refer to Great Britain, more the Roman province of Britain; this word derives from a Greek word, Πρεττανικη or Βρεττανίαι, used by Pytheas, an explorer from Massalia who visited the British Islands around 320 BC.
The Greek word itself comes from the common Brythonic ethnonym reconstructed as *Pritanī, itself from Proto-Celtic *kʷritanoi. The Romans called Brittany Armorica, together with a quite indefinite region that extended along the English Channel coast from the Seine estuary to the Loire estuary, according to several sources, maybe along the Atlantic coast to the Garonne estuary; this term comes from a Gallic word, which means "close to the sea". Another name, was used until the 12th century, it means "wide and flat" or "to expand" and it gave the Welsh name for Brittany: Llydaw. After the fall of the Western Roman Empire, many Britons settled in western Armorica, the region started to be called Britannia, although this name only replaced Armorica in the sixth century or by the end of the fifth. Authors like Geoffrey of Monmouth used the terms Britannia minor and Britannia major to distinguish Brittany from Britain. Breton-speaking people may pronounce the word Breizh in two different ways, according to their region of origin.
Breton can be divided into the dialect of Vannes. KLT speakers pronounce it and would write it Breiz, while the Vannetais speakers pronounce it and would write it Breih; the official spelling is a compromise with a z and an h together. In 1941, efforts to unify the dialects led to the creation of the so-called Breton zh, a standard which has never been accepted. On its side, Gallo language has never had a accepted writing system and several ones coexist. For instance, the name of the region in that language can be written Bertaèyn in ELG script, or Bertègn in MOGA, a couple of other scripts exist. Brittany has been inhabited by humans since the Lower Paleolithic; the first settlers were Neanderthals. This population was scarce and similar to the other Neanderthals found in the whole of Western Europe, their only original feature was a distinct culture, called "Colombanian". One of the oldest hearths in the world has been found in Finistère, it is 450,000 years old. Homo sapiens settled in Brittany around 35,000 years ago.
They replaced or absorbed the Neanderthals and developed local industries, similar to the Châtelperronian or to the Magdalenian. After the last glacial period, the warmer climate allowed the area to become wooded. At that time, Brittany was populated by large communities who started to change their lifestyles from a life of hunting and gathering, to become settled farmers. Agriculture was introduced during the 5th millennium BC by migrants from the east. However, the Neolithic Revolution in Brittany did not happen due to a radical change of population, but by slow immigration and exchange of skills. Neolithic Brittany is characterised by important megalithic production, it is sometimes designated as the "core area" of megalithic culture; the oldest monuments, were followed by princely tombs and stone rows. The Morbihan département, on the southern coast, comprises a large share of these structures, including the Carnac stones and the Broken Menhir of Er Grah in the Locmariaquer megaliths, the largest single stone erected by Neoli
Sweden the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, is connected to Denmark in the southwest by a bridge-tunnel across the Öresund, a strait at the Swedish-Danish border. At 450,295 square kilometres, Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. Sweden has a total population of 10.2 million. It has a low population density of 22 inhabitants per square kilometre; the highest concentration is in the southern half of the country. Germanic peoples have inhabited Sweden since prehistoric times, emerging into history as the Geats and Swedes and constituting the sea peoples known as the Norsemen. Southern Sweden is predominantly agricultural, while the north is forested. Sweden is part of the geographical area of Fennoscandia; the climate is in general mild for its northerly latitude due to significant maritime influence, that in spite of this still retains warm continental summers.
Today, the sovereign state of Sweden is a constitutional monarchy and parliamentary democracy, with a monarch as head of state, like its neighbour Norway. The capital city is Stockholm, the most populous city in the country. Legislative power is vested in the 349-member unicameral Riksdag. Executive power is exercised by the government chaired by the prime minister. Sweden is a unitary state divided into 21 counties and 290 municipalities. An independent Swedish state emerged during the early 12th century. After the Black Death in the middle of the 14th century killed about a third of the Scandinavian population, the Hanseatic League threatened Scandinavia's culture and languages; this led to the forming of the Scandinavian Kalmar Union in 1397, which Sweden left in 1523. When Sweden became involved in the Thirty Years War on the Reformist side, an expansion of its territories began and the Swedish Empire was formed; this became one of the great powers of Europe until the early 18th century. Swedish territories outside the Scandinavian Peninsula were lost during the 18th and 19th centuries, ending with the annexation of present-day Finland by Russia in 1809.
The last war in which Sweden was directly involved was in 1814, when Norway was militarily forced into personal union. Since Sweden has been at peace, maintaining an official policy of neutrality in foreign affairs; the union with Norway was peacefully dissolved in 1905. Sweden was formally neutral through both world wars and the Cold War, albeit Sweden has since 2009 moved towards cooperation with NATO. After the end of the Cold War, Sweden joined the European Union on 1 January 1995, but declined NATO membership, as well as Eurozone membership following a referendum, it is a member of the United Nations, the Nordic Council, the Council of Europe, the World Trade Organization and the Organisation for Economic Co-operation and Development. Sweden maintains a Nordic social welfare system that provides universal health care and tertiary education for its citizens, it has the world's eleventh-highest per capita income and ranks in numerous metrics of national performance, including quality of life, education, protection of civil liberties, economic competitiveness, equality and human development.
The name Sweden was loaned from Dutch in the 17th century to refer to Sweden as an emerging great power. Before Sweden's imperial expansion, Early Modern English used Swedeland. Sweden is derived through back-formation from Old English Swēoþēod, which meant "people of the Swedes"; this word is derived from Sweon/Sweonas. The Swedish name Sverige means "realm of the Swedes", excluding the Geats in Götaland. Variations of the name Sweden are used in most languages, with the exception of Danish and Norwegian using Sverige, Faroese Svøríki, Icelandic Svíþjóð, the more notable exception of some Finnic languages where Ruotsi and Rootsi are used, names considered as referring to the people from the coastal areas of Roslagen, who were known as the Rus', through them etymologically related to the English name for Russia; the etymology of Swedes, thus Sweden, is not agreed upon but may derive from Proto-Germanic Swihoniz meaning "one's own", referring to one's own Germanic tribe. Sweden's prehistory begins in the Allerød oscillation, a warm period around 12,000 BC, with Late Palaeolithic reindeer-hunting camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania.
This period was characterised by small bands of hunter-gatherer-fishers using flint technology. Sweden is first described in a written source in Germania by Tacitus in 98 AD. In Germania 44 and 45 he mentions the Swedes as a powerful tribe with ships that had a prow at each end. Which kings ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC; as for literacy in Sweden itself, the runic script was in use among the south Scandinavian elite by at least the 2nd century AD, but all that has come down to the present from the Roman Period is curt inscriptions on artefacts of male names, demonstrating th
The littoral zone or nearshore is the part of a sea, lake or river, close to the shore. In coastal environments the littoral zone extends from the high water mark, inundated, to shoreline areas that are permanently submerged, it always includes this intertidal zone and is used to mean the same as the intertidal zone. However, the meaning of "littoral zone" can extend well beyond the intertidal zone. There is no single definition. What is regarded as the full extent of the littoral zone, the way the littoral zone is divided into subregions, varies in different contexts; the use of the term varies from one part of the world to another, between different disciplines. For example, military commanders speak of the littoral in ways that are quite different from marine biologists; the adjacency of water gives a number of distinctive characteristics to littoral regions. The erosive power of water results in particular types of landforms, such as sand dunes, estuaries; the natural movement of the littoral along the coast is called the littoral drift.
Biologically, the ready availability of water enables a greater variety of plant and animal life, the formation of extensive wetlands. In addition, the additional local humidity due to evaporation creates a microclimate supporting unique types of organisms; the word "littoral" is used both as an adjective. It derives from the Latin noun litus, meaning "shore". In oceanography and marine biology, the idea of the littoral zone is extended to the edge of the continental shelf. Starting from the shoreline, the littoral zone begins at the spray region just above the high tide mark. From here, it moves to the intertidal region between the high and low water marks, out as far as the edge of the continental shelf; these three subregions are called, in order, the supralittoral zone, the eulittoral zone and the sublittoral zone. The supralittoral zone is the area above the spring high tide line, splashed, but not submerged by ocean water. Seawater penetrates these elevated areas only during storms with high tides.
Organisms here must cope with exposure to fresh water from rain, cold and predation by land animals and seabirds. At the top of this area, patches of dark lichens can appear as crusts on rocks; some types of periwinkles and detritus feeding Isopoda inhabit the lower supralittoral. The eulittoral zone is the intertidal zone known as the foreshore, it extends from the spring high tide line, inundated, to the spring low tide line, not inundated. The wave action and turbulence of recurring tides shapes and reforms cliffs and caves, offering a huge range of habitats for sedentary organisms. Protected rocky shorelines show a narrow homogenous eulittoral strip marked by the presence of barnacles. Exposed sites show a wider extension and are divided into further zones. For more on this, see intertidal ecology; the sublittoral zone starts below the eulittoral zone. This zone is permanently covered with seawater and is equivalent to the neritic zone. In physical oceanography, the sublittoral zone refers to coastal regions with significant tidal flows and energy dissipation, including non-linear flows, internal waves, river outflows and oceanic fronts.
In practice, this extends to the edge of the continental shelf, with depths around 200 meters. In marine biology, the sublittoral refers to the areas where sunlight reaches the ocean floor, that is, where the water is never so deep as to take it out of the photic zone; this results in high primary production and makes the sublittoral zone the location of the majority of sea life. As in physical oceanography, this zone extends to the edge of the continental shelf; the benthic zone in the sublittoral is much more stable than in the intertidal zone. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones. Within the sublittoral, marine biologists identify the following: The infralittoral zone is the algal dominated zone to maybe five metres below the low water mark; the circalittoral zone is the region beyond the infralittoral, that is, below the algal zone and dominated by sessile animals such as oysters. Shallower regions of the sublittoral zone, extending not far from the shore, are sometimes referred to as the subtidal zone.
In freshwater situations, littoral zones occur on the edge of large lakes and rivers with extensive areas of wetland. Hence, they are sometimes referred to as fringing wetlands. Here, the effects of tides are minimal. For example, the Minnesota Department of Natural Resources defines littoral as that portion of the lake, less than 15 feet in depth; the littoral zone may form a narrow or broad fringing wetland, with extensive areas of aquatic plants sorted by their tolerance to different water depths. Four zones are recognized, from higher to lower on the shore: wooded wetland, wet meadow and aquatic vegetation; the relative areas of these four types depends not only on the profile of the shoreline, but upon past water levels. The area of wet meadow is dependent upon past water levels.
The intertidal zone known as the foreshore and seashore and sometimes referred to as the littoral zone, is the area, above water at low tide and underwater at high tide. This area can include many different types of habitats, with many types of animals, such as starfish, sea urchins, numerous species of coral; the well-known area includes steep rocky cliffs, sandy beaches, or wetlands. The area can be a narrow strip, as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slopes interact with high tidal excursion. Peritidal zone is similar but a somewhat wider zone, extending from above the highest tide level to below that of the lowest tide level. Organisms in the intertidal zone are adapted to an environment of harsh extremes; the intertidal zone is home to many several species from different taxa including Porifera, Coelenterates, crustaceans, etc. Water is available with the tides but varies from fresh with rain to saline and dry salt with drying between tidal inundations.
Wave splash can dislodge residents from the littoral zone. With the intertidal zone's high exposure to the sun, the temperature range can be anything from hot with full sun to near freezing in colder climates; some microclimates in the littoral zone are ameliorated by local features and larger plants such as mangroves. Adaptation in the littoral zone allows the use of nutrients supplied in high volume on a regular basis from the sea, moved to the zone by tides. Edges of habitats, in this case land and sea, are themselves significant ecologies, the littoral zone is a prime example. A typical rocky shore can be divided into a spray zone or splash zone, above the spring high-tide line and is covered by water only during storms, an intertidal zone, which lies between the high and low tidal extremes. Along most shores, the intertidal zone can be separated into the following subzones: high tide zone, middle tide zone, low tide zone; the intertidal zone is one of a number of marine biomes or habitats, including estuaries, neritic and deep zones.
Marine biologists divide the intertidal region into three zones, based on the overall average exposure of the zone. The low intertidal zone, which borders on the shallow subtidal zone, is only exposed to air at the lowest of low tides and is marine in character; the mid intertidal zone is exposed and submerged by average tides. The high intertidal zone is only covered by the highest of the high tides, spends much of its time as terrestrial habitat; the high intertidal zone borders on the splash zone. On shores exposed to heavy wave action, the intertidal zone will be influenced by waves, as the spray from breaking waves will extend the intertidal zone. Depending on the substratum and topography of the shore, additional features may be noticed. On rocky shores, tide pools form in depressions. Under certain conditions, such as those at Morecambe Bay, quicksand may form; this subregion is submerged - it is only exposed at the point of low tide and for a longer period of time during low tides. This area is teeming with life.
There is a great biodiversity. Organisms in this zone are not well adapted to periods of dryness and temperature extremes; some of the organisms in this area are abalone, sea anemones, brown seaweed, crabs, green algae, isopods, mussels, sculpin, sea cucumber, sea lettuce, sea palms, sea urchins, snails, surf grass, tube worms, whelks. Creatures in this area can grow to larger sizes because there is more available energy in the localized ecosystem. Marine vegetation can grow to much greater sizes than in the other three intertidal subregions due to the better water coverage; the water is shallow enough to allow plenty of light to reach the vegetation to allow substantial photosynthetic activity, the salinity is at normal levels. This area is protected from large predators such as fish because of the wave action and the shallow water; the intertidal region is an important model system for the study of ecology on wave-swept rocky shores. The region contains a high diversity of species, the zonation created by the tides causes species ranges to be compressed into narrow bands.
This makes it simple to study species across their entire cross-shore range, something that can be difficult in, for instance, terrestrial habitats that can stretch thousands of kilometres. Communities on wave-swept shores have high turnover due to disturbance, so it is possible to watch ecological succession over years rather than decades; the burrowing invertebrates that make up large portions of sandy beach ecosystems are known to travel great distances in cross-shore directions as beaches change on the order of days, semilunar cycles, seasons, or years. The distribution of some species has been found to correlate with geomorphic datums such as the high tide strand and the water table outcrop. Since the foreshore is alternately covered by the sea and exposed to the air, organisms living in this environment must have adaptions for both wet and dry conditions. Hazards include being smashed or carried away by rough waves, exposure to dangerously high temperatures, desiccation. Typical inhabit