The British Isles are a group of islands in the North Atlantic off the north-western coast of continental Europe that consist of the islands of Great Britain, the Isle of Man, the Hebrides and over six thousand smaller isles. They have a total area of about 315,159 km2 and a combined population of 72 million, include two sovereign states, the Republic of Ireland, the United Kingdom of Great Britain and Northern Ireland; the islands of Alderney, Jersey and Sark, their neighbouring smaller islands, are sometimes taken to be part of the British Isles though, as islands off the coast of France, they do not form part of the archipelago. The oldest rocks in the group are in the north west of Scotland and North Wales and are 2.7 billion years old. During the Silurian period, the north-western regions collided with the south-east, part of a separate continental landmass; the topography of the islands is modest in scale by global standards. Ben Nevis rises to an elevation of only 1,345 metres, Lough Neagh, notably larger than other lakes in the island group, covers 390 square kilometres.
The climate is temperate marine, with warm summers. The North Atlantic drift brings significant moisture and raises temperatures 11 °C above the global average for the latitude; this led to a landscape, long dominated by temperate rainforest, although human activity has since cleared the vast majority of forest cover. The region was re-inhabited after the last glacial period of Quaternary glaciation, by 12,000 BC, when Great Britain was still part of a peninsula of the European continent. Ireland, which became an island by 12,000 BC, was not inhabited until after 8000 BC. Great Britain became an island by 5600 BC. Hiberni and Britons tribes, all speaking Insular Celtic, inhabited the islands at the beginning of the 1st millennium AD. Much of Brittonic-occupied Britain was conquered by the Roman Empire from AD 43; the first Anglo-Saxons arrived as Roman power waned in the 5th century, dominated the bulk of what is now England. Viking invasions began in the 9th century, followed by more permanent settlements and political change in England.
The Norman conquest of England in 1066 and the Angevin partial conquest of Ireland from 1169 led to the imposition of a new Norman ruling elite across much of Britain and parts of Ireland. By the Late Middle Ages, Great Britain was separated into the Kingdoms of England and Kingdom of Scotland, while control in Ireland fluxed between Gaelic kingdoms, Hiberno-Norman lords and the English-dominated Lordship of Ireland, soon restricted only to The Pale; the 1603 Union of the Crowns, Acts of Union 1707 and Acts of Union 1800 attempted to consolidate Britain and Ireland into a single political unit, the United Kingdom of Great Britain and Ireland, with the Isle of Man and the Channel Islands remaining as Crown Dependencies. The expansion of the British Empire and migrations following the Irish Famine and Highland Clearances resulted in the dispersal of some of the islands' population and culture throughout the world, a rapid depopulation of Ireland in the second half of the 19th century. Most of Ireland seceded from the United Kingdom after the Irish War of Independence and the subsequent Anglo-Irish Treaty, with six counties remaining in the UK as Northern Ireland.
The term "British Isles" is controversial in Ireland, where there are nationalist objections to its usage. The Government of Ireland does not recognise the term, its embassy in London discourages its use. Britain and Ireland is used as an alternative description, Atlantic Archipelago has seen limited use in academia; the earliest known references to the islands as a group appeared in the writings of sea-farers from the ancient Greek colony of Massalia. The original records have been lost. In the 1st century BC, Diodorus Siculus has Prettanikē nēsos, "the British Island", Prettanoi, "the Britons". Strabo used Βρεττανική, Marcian of Heraclea, in his Periplus maris exteri, used αἱ Πρεττανικαί νῆσοι to refer to the islands. Historians today, though not in absolute agreement agree that these Greek and Latin names were drawn from native Celtic-language names for the archipelago. Along these lines, the inhabitants of the islands were called the Πρεττανοί; the shift from the "P" of Pretannia to the "B" of Britannia by the Romans occurred during the time of Julius Caesar.
The Greco-Egyptian scientist Claudius Ptolemy referred to the larger island as great Britain and to Ireland as little Britain in his work Almagest. In his work, Geography, he gave these islands the names Alwion and Mona, suggesting these may have been names of the individual islands not known to him at the time of writing Almagest; the name Albion appears to have fallen out of use sometime after the Roman conquest of Great Britain, after which Britain became the more commonplace name for the island called Great Britain. The earliest known use of the phrase Brytish Iles in the English language is dated 1577 in a work by John Dee. Today, this name is seen by some as carrying imperialist overtones although it is still used. Other names used to describe the islands include the Anglo-Celtic Isles, Atlantic archipelago, British-Irish Isles and Ireland, UK
Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, petrology. In general a stratum will be igneous or sedimentary relating to how the rock was formed. Sedimentary layers are laid down by deposition of sediment associated with weathering processes, decaying organic matters or through chemical precipitation; these layers are distinguishable as having many fossils and are important for the study of biostratigraphy. Igneous layers are either plutonic or volcanic in character depending upon the cooling rate of the rock; these layers are devoid of fossils and represent intrusions and volcanic activity that occurred over the geologic history of the area. There are a number of principles; when an igneous rock cuts across a formation of sedimentary rock we can say that the igneous intrusion is younger than the sedimentary rock. The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed stratum is younger than the one beneath and older than the one above it.
The principle of original horizontality states that the deposition of sediments occurs as horizontal beds. A lithostratigraphic unit conforms to the law of superposition, which state that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks; the principle of lateral continuity states that a set of bed extends and can be traceable over a large area. Lithostratigraphic units are defined on the basis of observable rock characteristics; the descriptions of strata based on physical appearance define facies. Lithostratigraphic units are only defined by lithic characteristics, not by age. Stratotype: A designated type of unit consisting of accessible rocks that contain clear-cut characteristics which are representative of a particular lithostratigraphic unit. Lithosome: Masses of rock of uniform character and having interchanging relationships with adjacent masses of different lithology. E.g.: shale lithosome, limestone lithosome. The fundamental Lithostratigraphic unit is the formation.
A formation is a lithologically distinctive stratigraphic unit, large enough to be mappable and traceable. Formations may be subdivided into members and beds and aggregated with other formations into groups and supergroups. Two types of contact: conformable and unconformable. Conformable: unbroken deposition, no break or hiatus; the surface strata resulting is called a conformity. Two types of contact between conformable strata: abrupt contacts and gradational contact. Unconformable: period of erosion/non-deposition; the surface stratum resulting is called an unconformity. Four types of unconformity: Angular unconformity: younger sediment lies upon an eroded surface of tilted or folded older rocks; the older rock dips at a different angle from the younger. Disconformity: the contact between younger and older beds is marked by visible, irregular erosional surfaces. Paleosol might develop right above the disconformity surface because of the non-deposition setting. Paraconformity: the bedding planes below and above the unconformity are parallel.
A time gap is present, as shown by a faunal break, but there is no erosion, just a period of non-deposition. Nonconformity: young sediments are deposited right above older igneous or metamorphic rocks. To correlate lithostratigraphic units, geologists define facies, look for key beds or key sequences that can be used as a datum. Direct correlation: based on lithology, structure, thickness… Indirect correlation: electric log correlation Biostratigraphy Chronostratigraphy Topostratigraphy Online stratigraphic column generator Tamu.edu: Lithostratigraphy USGS.gov: Lithostratigraphy Agenames
Skye, or the Isle of Skye, is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous centre dominated by the Cuillin, the rocky slopes of which provide some of the most dramatic mountain scenery in the country. Although it has been suggested that the Gaelic Sgitheanach describes a winged shape there is no definitive agreement as to the name's origins; the island has been occupied since the Mesolithic period, its history includes a time of Norse rule and a long period of domination by Clan MacLeod and Clan Donald. The 18th century Jacobite risings led to the breaking up of the clan system and subsequent Clearances that replaced entire communities with sheep farms, some of which involved forced emigrations to distant lands. Resident numbers declined from over 20,000 in the early 19th century to just under 9,000 by the closing decade of the 20th century. Skye's population increased by 4 per cent between 1991 and 2001.
About a third of the residents were Gaelic speakers in 2001, although their numbers are in decline, this aspect of island culture remains important. The main industries are tourism, agriculture and forestry. Skye is part of the Highland Council local government area; the island's largest settlement is Portree, its capital, known for its picturesque harbour. There are links to various nearby islands by ferry and, since 1995, to the mainland by a road bridge; the climate is mild and windy. The abundant wildlife includes red deer and Atlantic salmon; the local flora are dominated by heather moor, there are nationally important invertebrate populations on the surrounding sea bed. Skye has provided the locations for various novels and feature films and is celebrated in poetry and song; the first written references to the island are Roman sources such as the Ravenna Cosmography, which refers to Scitis and Scetis, which can be found on a map by Ptolemy. One possible derivation comes from skitis, an early Celtic word for winged, which may describe how the island's peninsulas radiate out from a mountainous centre.
Subsequent Gaelic-, Norse- and English-speaking peoples have influenced the history of Skye. Various etymologies have been proposed, such as the "winged isle" or "the notched isle" but no definitive solution has been found to date. In the Norse sagas Skye is called Skíð, for example in the Hákonar saga Hákonarsonar and a skaldic poem in the Heimskringla from c. 1230 contains a line that translates as "the hunger battle-birds were filled in Skye with blood of foemen killed". The island was referred to by the Norse as Skuy, Skýey or Skuyö; the traditional Gaelic name is An t-Eilean Sgitheanach, An t-Eilean Sgiathanach being a more recent and less common spelling. In 1549 Donald Munro, High Dean of the Isles, wrote of "Sky": "This Ile is callit Ellan Skiannach in Irish, to say in Inglish the wyngit Ile, be reason it has mony wyngis and pointis lyand furth fra it, throw the dividing of thir foirsaid Lochis." But the meaning of this Gaelic name is unclear. Eilean a' Cheò, which means island of the mist, is a poetic Gaelic name for the island.
At 1,656 square kilometres, Skye is the second-largest island in Scotland after Harris. The coastline of Skye is a series of peninsulas and bays radiating out from a centre dominated by the Cuillin hills. Malcolm Slesser suggested that its shape "sticks out of the west coast of northern Scotland like a lobster's claw ready to snap at the fish bone of Harris and Lewis" and W. H. Murray, commenting on its irregular coastline, stated that "Skye is sixty miles long, but what might be its breadth is beyond the ingenuity of man to state". Martin Martin, a native of the island, reported on it at length in a 1703 publication, his geological observations included a note that: There are marcasites black and white, resembling silver ore, near the village Sartle: there are in the same place several stones, which in bigness, shape, &c. resemble nutmegs, many rivulets here afford variegated stones of all colours. The Applesglen near Loch-Fallart has agate growing in it of different colours. Stones of a purple colour flow down the rivulets here after great rains.
The Black Cuillin, which are composed of basalt and gabbro, include twelve Munros and provide some of the most dramatic and challenging mountain terrain in Scotland. The ascent of Sgùrr a' Ghreadaidh is one of the longest rock climbs in Britain and the Inaccessible Pinnacle is the only peak in Scotland that requires technical climbing skills to reach the summit; these hills make demands of the hill walker that exceed any others found in Scotland and a full traverse of the Cuillin ridge may take 15–20 hours. The Red Hills to the south are known as the Red Cuillin, they are composed of granite that has weathered into more rounded hills with many long scree slopes on their flanks. The highest point of these hills is one of only two Corbetts on Skye; the northern peninsula of Trotternish is underlain by basalt, which provides rich soils and a variety of unusual rock features. The Kilt Rock is named after the tartan-like patterns in the 105 metres cliffs; the Quiraing is a spectacular series of rock pinnacles on the eastern side of th
The Hettangian is the earliest age and lowest stage of the Jurassic period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma. The Hettangian is followed by the Sinemurian. In European stratigraphy the Hettangian is a part of the time span. An example is the British Blue Lias. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but rare ammonites, including Alsatites, have been found; the Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier, in 1864. The stage takes its name from Hettange-Grande, a town in north-eastern France, just south of the border with Luxembourg on the main road from Luxembourg City to Metz; the base of the Hettangian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Psiloceras first appear. A global reference profile for the base was defined 2010 at the Kuhjoch in the Karwendel in western Austria; the top of the Hettangian stage is at the first appearances of ammonite genera Vermiceras and Metophioceras.
The Hettangian contains three ammonite biozones in the Tethys domain: zone of Schlotheimia angulata zone of Alsatites liasicus zone of Psiloceras planorbis At the end of the Triassic period, the ammonites died out entirely. During the Hettangian, the "Neoammonites" developed quickly, so that in the middle Hettangian a large number of genera and species existed. Triassic-Jurassic extinction event Komlosaurus carbonis Gradstein, F. M.. G. & Smith, A. G.. Renevier, E.: Notices géologiques et paléontologiques sur les Alpes Vaudoises, et les régions environnantes. I. Infralias et Zone à Avicula contorta des Alpes Vaudoises Bulletin de la Société Vaudoise des Sciences Naturelles 8, p. 39-97. GeoWhen Database - Hettangian Lower Jurassic timescale, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Lower Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
The North Sea is a marginal sea of the Atlantic Ocean located between the United Kingdom, Norway, Germany, the Netherlands and France. An epeiric sea on the European continental shelf, it connects to the ocean through the English Channel in the south and the Norwegian Sea in the north, it is more than 970 kilometres long and 580 kilometres wide, with an area of 570,000 square kilometres. The North Sea has long been the site of important European shipping lanes as well as a major fishery; the sea is a popular destination for recreation and tourism in bordering countries and more has developed into a rich source of energy resources including fossil fuels and early efforts in wave power. The North Sea has featured prominently in geopolitical and military affairs in Northern Europe, it was important globally through the power northern Europeans projected worldwide during much of the Middle Ages and into the modern era. The North Sea was the centre of the Vikings' rise. Subsequently, the Hanseatic League, the Netherlands, the British each sought to dominate the North Sea and thus access to the world's markets and resources.
As Germany's only outlet to the ocean, the North Sea continued to be strategically important through both World Wars. The coast of the North Sea presents a diversity of geographical features. In the north, deep fjords and sheer cliffs mark the Norwegian and Scottish coastlines, whereas in the south, the coast consists of sandy beaches and wide mudflats. Due to the dense population, heavy industrialization, intense use of the sea and area surrounding it, there have been various environmental issues affecting the sea's ecosystems. Adverse environmental issues – including overfishing and agricultural runoff and dumping, among others – have led to a number of efforts to prevent degradation of the sea while still making use of its economic potential; the North Sea is bounded by the Orkney Islands and east coast of Great Britain to the west and the northern and central European mainland to the east and south, including Norway, Germany, the Netherlands and France. In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean.
In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively. In the north it is bordered by the Shetland Islands, connects with the Norwegian Sea, which lies in the north-eastern part of the Atlantic; the North Sea is more than 970 kilometres long and 580 kilometres wide, with an area of 570,000 square kilometres and a volume of 54,000 cubic kilometres. Around the edges of the North Sea are sizeable islands and archipelagos, including Shetland and the Frisian Islands; the North Sea receives freshwater from a number of European continental watersheds, as well as the British Isles. A large part of the European drainage basin empties into the North Sea, including water from the Baltic Sea; the largest and most important rivers flowing into the North Sea are the Elbe and the Rhine – Meuse watershed. Around 185 million people live in the catchment area of the rivers discharging into the North Sea encompassing some industrialized areas.
For the most part, the sea lies on the European continental shelf with a mean depth of 90 metres. The only exception is the Norwegian trench, which extends parallel to the Norwegian shoreline from Oslo to an area north of Bergen, it has a maximum depth of 725 metres. The Dogger Bank, a vast moraine, or accumulation of unconsolidated glacial debris, rises to a mere 15 to 30 m below the surface; this feature has produced the finest fishing location of the North Sea. The Long Forties and the Broad Fourteens are large areas with uniform depth in fathoms; these great banks and others make the North Sea hazardous to navigate, alleviated by the implementation of satellite navigation systems. The Devil's Hole lies 200 miles east of Scotland; the feature is a series of asymmetrical trenches between 20 and 30 kilometres long and two kilometres wide and up to 230 metres deep. Other areas which are less deep are Fisher Bank and Noordhinder Bank; the International Hydrographic Organization defines the limits of the North Sea as follows: On the Southwest.
A line joining the Walde Lighthouse and Leathercoat Point. On the Northwest. From Dunnet Head in Scotland to Tor Ness in the Island of Hoy, thence through this island to the Kame of Hoy on to Breck Ness on Mainland through this island to Costa Head and to Inga Ness in Westray through Westray, to Bow Head, across to Mull Head and on to Seal Skerry and thence to Horse Island. On the North. From the North point of the Mainland of the Shetland Islands, across to Graveland Ness in the Island of Yell, through Yell to Gloup Ness and across to Spoo Ness in Unst island, through Unst to Herma Ness, on to the SW point of the Rumblings and to Muckle Flugga all these being included in the North Sea area.
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors; the Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; the term "Permian" was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic era. Large continental landmass interiors experience climates with extreme variations of heat and cold and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age. Glaciers receded around the mid-Permian period as the climate warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Permian marine deposits are rich in fossil mollusks and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between ~ 237 Ma; the Ladinian was succeeded by the Carnian. The Ladinian is coeval with the Falangian Chinese regional stage; the Ladinian was established by Austrian geologist Alexander Bittner in 1892. Its name comes from the Ladin people; the base of the Ladinian stage is defined as the place in the stratigraphic record where the ammonite species Eoprotrachyceras curionii first appears or the first appearance of the conodont Budurovignathus praehungaricus. The global reference profile for the base is at an outcrop in the river bed of the Caffaro river at Bagolino, in the province of Brescia, northern Italy; the top of the Ladinian is at the first appearance of ammonite species Daxatina canadensis. The Ladinian is sometimes subdivided into two subages or substages, the Fassanian and the Longobardian; the Ladinian contains four ammonite biozones, which are evenly distributed among the two substages: zone of Frechites regoledanus zone of Protrachyceras archelaus zone of Protrachyceras gredleri zone of Eoprotrachyceras curionii Many Ladinian and Carnian vertebrates have been discovered in the paleorrota in Brazil: Rhynchosaurs, exaeretodonts, Guaibasaurus, Saturnalia tupiniquim, Sacisaurus and many others.
Paleorrota lies within the Caturrita Formation. Vertebrates of Ladinian age include: Spondylosoma Dicynodonts Paleorrota Bittner, A.. Brack, P.. Gradstein, F. M.. G. & Smith, A. G.. GeoWhen Database - Ladinian Upper Triassic and Lower Triassic timescales, at the website of the subcommission for stratigraphic information of the ICS Norges Network of offshore records of geology and stratigraphy: Stratigraphic charts for the Triassic, and