A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is called a gulf, sound, or bight. A cove is a type of smaller bay with narrow entrance. A fjord is a steep bay shaped by glacial activity. A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may be nested within each other; some large bays, such as the Bay of Bengal and Hudson Bay, have varied marine geology. The land surrounding a bay reduces the strength of winds and blocks waves. Bays were significant in the history of human settlement because they provided safe places for fishing, they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports. The United Nations Convention on the Law of the Sea called the Law of the Sea, defines a bay as a well-marked indentation whose penetration is in such proportion to the width of its mouth as to contain land-locked waters and constitute more than a mere curvature of the coast.
An indentation shall not, however, be regarded as a bay unless its area is as large as, or larger than, that of the semi-circle whose diameter is a line drawn across the mouth of that indentation. There are various ways; the largest bays have developed through plate tectonics. As the super-continent Pangaea broke up along curved and indented fault lines, the continents moved apart and left large bays. Bays form through coastal erosion by rivers and glaciers. A bay formed by a glacier is a fjord. Rias are characterised by more gradual slopes. Deposits of softer rocks erode more forming bays, while harder rocks erode less leaving headlands. Bay platform Great capes Headlands and bays
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that protect the coral. Most reefs grow best in warm, clear and agitated water. Called "rainforests of the sea", shallow coral reefs form some of Earth's most diverse ecosystems, they occupy less than 0.1% of the world's ocean area, about half the area of France, yet they provide a home for at least 25% of all marine species, including fish, worms, echinoderms, sponges and other cnidarians. Coral reefs flourish in ocean waters, they are most found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. Coral reefs deliver ecosystem services for tourism and shoreline protection.
The annual global economic value of coral reefs is estimated between US$30–375 billion and 9.9 trillion USD. Coral reefs are fragile because they are sensitive to water conditions, they are under threat from excess nutrients, rising temperatures, oceanic acidification, sunscreen use, harmful land-use practices, including runoff and seeps. Most coral reefs were formed after the last glacial period when melting ice caused sea level to rise and flood continental shelves. Most coral reefs are less than 10,000 years old; as communities established themselves, the reefs grew pacing rising sea levels. Reefs that rose too could become drowned, without sufficient light. Coral reefs are found in the deep sea away from continental shelves, around oceanic islands and atolls; the majority of these islands are volcanic in origin. Others have tectonic origins. In The Structure and Distribution of Coral Reefs, Charles Darwin set out his theory of the formation of atoll reefs, an idea he conceived during the voyage of the Beagle.
He theorized that subsidence of the Earth's crust under the oceans formed the atolls. Darwin set out a sequence of three stages in atoll formation. A fringing reef forms around an extinct volcanic island as the ocean floor subsides; as the subsidence continues, the fringing reef becomes a barrier reef and an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast to form fringing reefs, can grow to become a barrier reef. Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies. If the land subsides the fringing reefs keep pace by growing upwards on a base of older, dead coral, forming a barrier reef enclosing a lagoon between the reef and the land.
A barrier reef can encircle an island, once the island sinks below sea level a circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs and atolls do not form complete circles, but are broken in places by storms. Like sea level rise, a subsiding bottom can overwhelm coral growth, killing the coral and the reef, due to what is called coral drowning. Corals that rely on zooxanthellae can die when the water becomes too deep for their symbionts to adequately photosynthesize, due to decreased light exposure; the two main variables determining the geomorphology, or shape, of coral reefs are the nature of the substrate on which they rest, the history of the change in sea level relative to that substrate. The 20,000-year-old Great Barrier Reef offers an example of how coral reefs formed on continental shelves. Sea level was 120 m lower than in the 21st century; as sea level rose, the water and the corals encroached on what had been hills of the Australian coastal plain.
By 13,000 years ago, sea level had risen to 60 m lower than at present, many hills of the coastal plains had become continental islands. As sea level rise continued, water topped most of the continental islands; the corals could overgrow the hills, forming cays and reefs. Sea level on the Great Barrier Reef has not changed in the last 6,000 years; the age of living reef structure is estimated to be between 8,000 years. Although the Great Barrier Reef formed along a continental shelf, not around a volcanic island, Darwin's principles apply. Development stopped at the barrier reef stage, it formed 300 -- 1,000 m from shore, stretching for 2,000 km. Healthy tropical coral reefs grow horizontally from 1 to 3 cm per year, grow vertically anywhere from 1 to 25 cm per year; as the name implies, coral reefs are made up of coral skeletons from intact coral colonies. As other chemical elements present in corals become incorporated into the calcium carbonate deposits, aragonite is formed. However
An anchialine pool or pond is a landlocked body of water with a subterranean connection to the ocean. Anchialine pools are a feature of coastal aquifers which are density stratified, with the water near the surface being fresh or brackish, saline water intruding from the coast below at some depth. Depending on the site, it is sometimes possible to access the deeper saline water directly in the anchialine pool or sometimes it may be accessible by cave diving. Water levels in anchialine pools fluctuate with tidal changes due to the coastal location and the connection with the ocean; the range in water levels fluctuations will be decreased and delayed compared to the range and time observed for the adjacent tide. The primary controls on the damping and lag are the distance from the coast, the hydraulic conductivity of the geological materials. Anchialine pools are common worldwide along Neotropical coastlines where the geology and aquifer system are young, there is minimal soil development; such conditions occur notably where the bedrock is limestone or formed volcanic lava.
Many anchialine pools are found on the coastlines of the island of Hawaii, on the Yucatán Peninsula, where they are locally called cenotes, as well as Christmas Island. The Sailor's Hat crater created by an explosives test in 1965 is an anchialine pool. Ecological studies of anchialine pools identify regionally rare and sometimes endemic species. In Hawaii, the pools are home to the ʻōpaeʻula. In karst anchialine pools and the caves these may be connected to, the fauna are diverse and include crustaceans, including remipedia and copepods, among the vertebrates are several species of blind cave fish. Brackish water Cenote Anchialine Pool Information United States Geological Survey, National Park Service 2005 Anchialine Caves and Cave Fauna of the World
Scotland is a country, part of the United Kingdom. Sharing a border with England to the southeast, Scotland is otherwise surrounded by the Atlantic Ocean to the north and west, by the North Sea to the northeast and by the Irish Sea to the south. In addition to the mainland, situated on the northern third of the island of Great Britain, Scotland has over 790 islands, including the Northern Isles and the Hebrides; the Kingdom of Scotland emerged as an independent sovereign state in the Early Middle Ages and continued to exist until 1707. By inheritance in 1603, James VI, King of Scots, became King of England and King of Ireland, thus forming a personal union of the three kingdoms. Scotland subsequently entered into a political union with the Kingdom of England on 1 May 1707 to create the new Kingdom of Great Britain; the union created a new Parliament of Great Britain, which succeeded both the Parliament of Scotland and the Parliament of England. In 1801, the Kingdom of Great Britain and Kingdom of Ireland enacted a political union to create a United Kingdom.
The majority of Ireland subsequently seceded from the UK in 1922. Within Scotland, the monarchy of the United Kingdom has continued to use a variety of styles and other royal symbols of statehood specific to the pre-union Kingdom of Scotland; the legal system within Scotland has remained separate from those of England and Wales and Northern Ireland. The continued existence of legal, educational and other institutions distinct from those in the remainder of the UK have all contributed to the continuation of Scottish culture and national identity since the 1707 union with England; the Scottish Parliament, a unicameral legislature comprising 129 members, was established in 1999 and has authority over those areas of domestic policy which have been devolved by the United Kingdom Parliament. The head of the Scottish Government, the executive of the devolved legislature, is the First Minister of Scotland. Scotland is represented in the UK House of Commons by 59 MPs and in the European Parliament by 6 MEPs.
Scotland is a member of the British–Irish Council, sends five members of the Scottish Parliament to the British–Irish Parliamentary Assembly. Scotland is divided into councils. Glasgow City is the largest subdivision in Scotland in terms of population, with Highland being the largest in terms of area. "Scotland" comes from the Latin name for the Gaels. From the ninth century, the meaning of Scotia shifted to designate Gaelic Scotland and by the eleventh century the name was being used to refer to the core territory of the Kingdom of Alba in what is now east-central Scotland; the use of the words Scots and Scotland to encompass most of what is now Scotland became common in the Late Middle Ages, as the Kingdom of Alba expanded and came to encompass various peoples of diverse origins. Repeated glaciations, which covered the entire land mass of modern Scotland, destroyed any traces of human habitation that may have existed before the Mesolithic period, it is believed the first post-glacial groups of hunter-gatherers arrived in Scotland around 12,800 years ago, as the ice sheet retreated after the last glaciation.
At the time, Scotland was covered in forests, had more bog-land, the main form of transport was by water. These settlers began building the first known permanent houses on Scottish soil around 9,500 years ago, the first villages around 6,000 years ago; the well-preserved village of Skara Brae on the mainland of Orkney dates from this period. Neolithic habitation and ritual sites are common and well preserved in the Northern Isles and Western Isles, where a lack of trees led to most structures being built of local stone. Evidence of sophisticated pre-Christian belief systems is demonstrated by sites such as the Callanish Stones on Lewis and the Maes Howe on Orkney, which were built in the third millennium BCE; the first written reference to Scotland was in 320 BC by Greek sailor Pytheas, who called the northern tip of Britain "Orcas", the source of the name of the Orkney islands. During the first millennium BCE, the society changed to a chiefdom model, as consolidation of settlement led to the concentration of wealth and underground stores of surplus food.
The first Roman incursion into Scotland occurred in 79 AD. After the Roman victory, Roman forts were set along the Gask Ridge close to the Highland line, but by three years after the battle, the Roman armies had withdrawn to the Southern Uplands; the Romans erected Hadrian's Wall in northern England and the Limes Britannicus became the northern border of the Roman Empire. The Roman influence on the southern part of the country was considerable, they introduced Christianity to Scotland. Beginning in the sixth century, the area, now Scotland was divided into three areas: Pictland, a patchwork of small lordships in central Scotland; these societies were based on the family unit and had sharp divisions in wealth, although the vast majority were poor and worked full-time in subsistence agriculture. The Picts kept slaves through the ninth century. Gaelic influence over Pictland and Northumbria was facilitated by the large number of Gaelic-speaking clerics working as missionaries. Operating in the sixth ce
An island or isle is any piece of sub-continental land, surrounded by water. Small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or a lake island may be called an eyot or ait, a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines. An island may be described despite the presence of an artificial land bridge; some places may retain "island" in their names for historical reasons after being connected to a larger landmass by a land bridge or landfill, such as Coney Island and Coronado Island, though these are speaking, tied islands. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal or Marble Hill in northern Manhattan during the time between the building of the United States Ship Canal and the filling-in of the Harlem River which surrounded the area, it is not considered an island.
There are two main types of islands in the sea: oceanic. There are artificial islands; the word island derives from Middle English iland, from Old English igland. However, the spelling of the word was modified in the 15th century because of a false etymology caused by an incorrect association with the etymologically unrelated Old French loanword isle, which itself comes from the Latin word insula. Old English ieg is a cognate of Swedish ö and German Aue, related to Latin aqua. Greenland is the world's largest island, with an area of over 2.1 million km2, while Australia, the world's smallest continent, has an area of 7.6 million km2, but there is no standard of size that distinguishes islands from continents, or from islets. There is a difference between continents in terms of geology. Continents are the largest landmass of a particular continental plate. By contrast, islands are either extensions of the oceanic crust, or belong to a continental plate containing a larger landmass. Continental islands are bodies of land.
Examples are Borneo, Sumatra, Sakhalin and Hainan off Asia. A special type of continental island is the microcontinental island, created when a continent is rifted. Examples are Madagascar and Socotra off Africa, New Caledonia, New Zealand, some of the Seychelles. Another subtype is an island or bar formed by deposition of tiny rocks where water current loses some of its carrying capacity; this includes: barrier islands, which are accumulations of sand deposited by sea currents on the continental shelves fluvial or alluvial islands formed in river deltas or midstream within large rivers. While some are transitory and may disappear if the volume or speed of the current changes, others are stable and long-lived. Islets are small islands. Oceanic islands are islands; the vast majority are volcanic in origin, such as Saint Helena in the South Atlantic Ocean. The few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the ocean floor above the surface.
Examples are Saint Paul Rocks in the Atlantic Ocean and Macquarie Island in the Pacific. One type of volcanic oceanic island is found in a volcanic island arc; these islands arise from volcanoes. Examples are the Aleutian Islands, the Mariana Islands, most of Tonga in the Pacific Ocean; the only examples in the Atlantic Ocean are some of the Lesser Antilles and the South Sandwich Islands. Another type of volcanic oceanic island occurs. There are two examples: Iceland, the world's second largest volcanic island, Jan Mayen. Both are in the Atlantic. A third type of volcanic oceanic island is formed over volcanic hotspots. A hotspot is more or less stationary relative to the moving tectonic plate above it, so a chain of islands results as the plate drifts. Over long periods of time, this type of island is "drowned" by isostatic adjustment and eroded, becoming a seamount. Plate movement across a hot-spot produces a line of islands oriented in the direction of the plate movement. An example is the Hawaiian Islands, from Hawaii to Kure, which continue beneath the sea surface in a more northerly direction as the Emperor Seamounts.
Another chain with similar orientation is the Tuamotu Archipelago. The southernmost chain is the Austral Islands, with its northerly trending part the atolls in the nation of Tuvalu. Tristan da Cunha is an example of a hotspot volcano in the Atlantic Ocean. Another hotspot in the Atlantic is the island of Surtsey, formed in 1963. An atoll is an island formed from a coral reef that has grown on an eroded and submerged volcanic island; the reef forms a new island. Atolls are ring-shaped with a central lagoon. Examples are the Line Islands
St Ninian's Isle
St Ninian's Isle is a small tied island connected by the largest tombolo in the UK to the south-western coast of the Mainland, Shetland, in Scotland. It is part of the civil parish of Dunrossness on the South Mainland; the tombolo, known locally as an ayre from the Old Norse for "gravel bank", is 500 metres long. During the summer the tombolo accessible to walkers. During winter, stronger wave action removes sand from the beach so that it is covered at high tide, throughout the tidal cycle, until the sand is returned the following spring. Depending on the definition used, St. Ninian's is thus either a peninsula; the nearest settlement is Bigton in the parish of Dunrossness. The important early medieval St Ninian's Isle Treasure of metalwork in silver, was discovered under the church floor in 1958. Many seabirds, including puffins, visit the island, with several species nesting there; as its name suggests, the island has ecclesiastical connections, which may like others in the Northern Isles and Faroes have connections to the Culdees or papar.
However, the island's history is far older than Christianity, Neolithic graves have been found within the walls of the chapel. The ruins of a 12th-century chapel can still be seen near the end of the tombolo; the dedication is to Shetland's patron saint, the enigmatic Saint Ninian of Galloway, widely venerated on the nearby Orkney Islands, may be commemorated in the name of North Ronaldsay. In 1958, an excavation found a hoard of 8th century silver in the chapel grounds under a stone slab in a wooden box, which caused a renewed archaeological interest in the island, it was suspected to have been stolen in, a Viking raid. The remains of a pre-Norse chapel were found, which may indicate some kind of Culdee presence; the last family to live on the island, that of Henry Leask, left the island in 1796. Henry Leask had 13 children; the St Ninian's Isle Treasure was discovered under a cross-marked slab in the floor of the early St. Ninian's church, on 4 July 1958 by a local schoolboy, Douglas Coutts.
Coutts was helping visiting archaeologists led by Professor A. C. O'Dell of Aberdeen University at a dig on the isle; the silver bowls and other pieces are believed to date from approx. 800 AD. O'Dell, A. St. Ninian's Isle Treasure. A Silver Hoard Discovered on St. Ninian's Isle, Zetland on 4th July, 1958. Aberdeen University Studies. No. 141 Nicolson, James R. Shetland. Newton Abbott. David & Charles. Youngs, Susan, "The Work of Angels", Masterpieces of Celtic Metalwork, 6th–9th centuries AD, pp. 108–112, 1989, British Museum Press, London, ISBN 978-0-7141-0554-3 Webster, Anglo-Saxon Art, 2012, British Museum Press, ISBN 9780714128092 Photographs of the St Ninian's Isle Treasure, at the National Museums Scotland website Shetland Museum - Pictures of the treasure St Ninian's Isle - Shetland Heritage St Ninian's Isle Treasure on Shetlopedia