The South Downs are a range of chalk hills that extends for about 260 square miles across the south-eastern coastal counties of England from the Itchen Valley of Hampshire in the west to Beachy Head, in the Eastbourne Downland Estate, East Sussex, in the east. The Downs are bounded on the northern side by a steep escarpment, from whose crest there are extensive views northwards across the Weald; the South Downs National Park forms a much larger area than the chalk range of the South Downs and includes large parts of the Weald. The South Downs are characterised by rolling chalk downland with close-cropped turf and dry valleys, are recognised as one of the most important chalk landscapes in England; the range is one of the four main areas of chalk downland in southern England. The South Downs are less populated compared to South East England as a whole, although there has been large-scale urban encroachment onto the chalk downland by major seaside resorts, including most notably Brighton and Hove.
The South Downs have been inhabited since ancient times and at periods the area has supported a large population during Romano-British times. There is a rich heritage of historical features and archaeological remains, including defensive sites, burial mounds and field boundaries. Within the South Downs Environmentally Sensitive Area there are thirty-seven Sites of Special Scientific Interest, including large areas of chalk grassland; the grazing of sheep on the thin, well-drained chalk soils of the Downs over many centuries and browsing by rabbits resulted in the fine, springy turf, known as old chalk grassland, that has come to epitomise the South Downs today. Until the middle of the 20th century, an agricultural system operated by downland farmers known as'sheep-and-corn farming' underpinned this: the sheep of villagers would be systematically confined to certain corn fields to improve their fertility with their droppings and they would be let out onto the downland to graze. However, starting in 1940 with government measures during World War II to increase domestic food production and continuing into the 1950s, much grassland was ploughed up for arable farming, fundamentally changing the landscape and ecology, with the loss of much biodiversity.
As a result, while old chalk grassland accounted for 40-50% of the eastern Downs before the war, only 3-4% survives. This and development pressures from the surrounding population centres led to the decision to create the South Downs National Park, which came into full operation on 1 April 2011, to protect and restore the Downs; the South Downs have been designated as a National Character Area by Natural England. It is bordered by the Hampshire Downs, the Wealden Greensand, the Low Weald and the Pevensey Levels to the north and the South Hampshire Lowlands and South Coast Plain to the south; the downland is a popular recreational destination for walkers and mountain bikers. A long distance footpath and bridleway, the South Downs Way, follows the entire length of the chalk ridge from Winchester to Eastbourne, complemented by many interconnecting public footpaths and bridleways; the term'downs' is from Old English dūn, meaning'hill'. The word acquired the sense of'elevated rolling grassland' around the fourteenth century.
These hills are prefixed'south' to distinguish them from another chalk escarpment, the North Downs, which runs parallel to them about 30 miles away on the northern edge of the Weald. The South Downs are formed from a thick band of chalk, deposited during the Cretaceous Period around sixty million years ago within a shallow sea which extended across much of northwest Europe; the rock is composed of the microscopic skeletons of plankton which lived in the sea, hence its colour. The chalk has many fossils, bands of flint occur throughout the formation; the Chalk is divided into the Lower and Upper Chalk, a thin band of cream-coloured nodular chalk known as the Melbourn Rock marking the boundary between the Lower and Middle units. The strata of southeast England, including the Chalk, were folded during a phase of the Alpine Orogeny to produce the Weald-Artois Anticline, a dome-like structure with a long east-west axis. Erosion has removed the central part of the dome, leaving the north-facing escarpment of the South Downs along its southern margin with the south-facing chalk escarpment of the North Downs as its counterpart on the northern side, as shown on the diagram.
Between these two escarpments the anticline has been subject to differential erosion so that geologically distinct areas of hills and vales lie in concentric circles towards the centre. The chalk, being porous, allows water to soak through; the South Downs are a long chalk escarpment that stretches for over 110 kilometres, rising from the valley of the River Itchen near Winchester, Hampshire, in the west to Beachy Head near Eastbourne, East Sussex, in the east. Behind the steep north-facing scarp slope, the inclined dip slope of undulating chalk downland extends for a distance of up to 7 miles southwards. Viewed from high points further north in the High Weald and on the North Downs, the scarp of the South Downs presents itself as a steep wall that bounds the horizon, with its grassland heights punctuat
Lists of mountains and hills in the British Isles
The mountains and hills of the British Isles are categorised into lists based on elevation and other criteria. These lists are used for peak bagging, whereby hillwalkers attempt to reach all the summits on a list, the oldest and best-known, being the 282 § Munros in Scotland, which amongst other criteria, must be above 3,000 feet. A height above 2,000 ft, or more latterly 600 m, is considered necessary to be a "mountain" in the British Isles, apart from the Munros, all lists require a prominence of at least 15 metres. A prominence of between 15–30 metres, does not meet the UIAA definition of an "independent" peak. Most lists consider a prominence between 30–150 metres as a "top", not a mountain. A popular designation are the § Marilyns, with a prominence above 150 metres. Prominences above 600 metres, are the § P600, the international classification of a "major" mountain. There is no worldwide consensus on the definition of "mountain", but in Great Britain and Ireland it is taken to be any summit at least 2,000 feet high.
The UK government defines mountain as land over 600 metres for the purposes of freedom of access. When Calf Top in Cumbria, was re-surveyed 2016 and confirmed to be exactly 2,000 ft, 6 millimetres above the 609.6 m threshold for a 2,000 ft peak, the Ordnance Survey described Calf Top as England's "last mountain". List of mountains of the British Isles by height, a ranking by height and prominence on the Simms classification List of Marilyns in the British Isles, a ranking by height and prominence on the Marilyn classification List of P600 mountains in the British Isles, a ranking by height and prominence on the P600 classification In addition, all British Isles definitions, with the exception of definitions that rely on § Isolation, include a minimum topographical prominence requirement, 30–600 m; the lowest minimum prominence is 15 metres, the Nuttalls and Vandeleur-Lynams, however most definitions do not consider prominences below 30 metres. Many definitions use the term Tops to refer to the sub-class of peaks that do not meet a 150 metres prominence threshold for the main definition, but have a prominence of between 30–150 metres.
Some definitions ignore height and just focus purely on prominence. Prominence requirements are strongly debated regarding UIAA classification of major Himalayan mountains. In 1994, regarding classification of summits, the UIAA stated that for a "peak" to be independent, it needed a prominence over 30 m, in addition, a "mountain" had to have a prominence over 300 m. Unlike the single measurement of elevation, prominence requires the detailed measurement of all contours around the peak, is therefore subject to change and revision over time, thus tables based on prominence are subject to revision; some definitions use an imperial measurement for height, but a metric measurement for the topological prominence. List of mountains of the British Isles by height, a ranking by height and prominence on the Simms classification List of Marilyns in the British Isles, a ranking by height and prominence on the Marilyn classification List of P600 mountains in the British Isles, a ranking by height and prominence on the P600 classification No definition of a British Isles mountain or hill uses an explicit quantitative metric of topographic isolation, the concept of isolation is embedded in the qualitative definition of a Scottish Munro, from the Scottish Mountaineering Club requirement of "sufficient separation".
Mountains in Scotland are referred to as "hills" no matter what their height, as reflected in names such as the Cuillin Hills and the Torridon Hills. The Database of British and Irish Hills was created in 2001 "with the intention of providing a comprehensive, up-to-date resource for British hillwalkers", it is now maintained by a team of eight editors, is described by the Long Distance Walkers Association as "now the most reliable online source for all Registers". The DoBIH has been used as a source by books, hillwalking websites and smartphone apps, including Mark Jackson's 2010 book on the HuMPS, titled "More Relative Hills of Britain". DoBIH is available in an online version under the title Hill Bagging; as of August 2018 the database included 20,859 hills, including all Marilyns, HuMPs, TuMPs, Dodds and Tops, Corbetts and Tops and Tops, Donalds and Tops, Hewitts, Buxton & Lewis, Murdos, Donald Deweys, Highland Fives, Birketts, Fellrangers, County tops, SIBs, Arderins, Vandeleur-Lynams, Myrddyn Deweys and Binnions, "with subs and deletions".
Since 2012, the DoBIH has a data-sharing agreement with the Irish online database of mountains and hills, called MountainViews. The P600s are mountains in the British Isles that have a topographical prominence of at leas
A hillfort is a type of earthworks used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are European and of the Bronze and Iron Ages; some were used in the post-Roman period. The fortification follows the contours of a hill, consisting of one or more lines of earthworks, with stockades or defensive walls, external ditches. Hillforts developed in the Late Bronze and Early Iron Age the start of the first millennium BC, were used in many Celtic areas of central and western Europe until the Roman conquest; the terms "hill fort", "hill-fort" and "hillfort" are all used in the archaeological literature. They all refer to an elevated site with one or more ramparts made of earth, stone and/or wood, with an external ditch. Many small early hillforts were abandoned, with the larger ones being redeveloped at a date; some hillforts contain houses. Similar but smaller and less defendable earthworks are found on the sides of hills; these may have been animal pens.
They are most common during periods: Urnfield culture and Atlantic Bronze Age Bronze Age Hallstatt culture late Bronze Age to early Iron Age La Tène culture late Iron AgePrehistoric Europe saw a growing population. It has been estimated that in about 5000 BC during the Neolithic between 2 million and 5 million lived in Europe. Outside Greece and Italy, which were more densely populated, the vast majority of settlements in the Iron Age were small, with no more than 50 inhabitants. Hillforts were the exception, were the home of up to 1,000 people. With the emergence of oppida in the Late Iron Age, settlements could reach as large as 10,000 inhabitants; as the population increased so did the complexity of prehistoric societies. Around 1100 BC hillforts in the following centuries spread through Europe, they served a range of purposes and were variously tribal centres, defended places, foci of ritual activity, places of production. During the Hallstatt C period, hillforts became the dominant settlement type in the west of Hungary.
Julius Caesar described the large late Iron Age hillforts he encountered during his campaigns in Gaul as oppida. By this time the larger ones had become more like cities than fortresses and many were assimilated as Roman towns. Hillforts were occupied by conquering armies, but on other occasions the forts were destroyed, the local people forcibly evicted, the forts left derelict. For example, Solsbury Hill was sacked and deserted during the Belgic invasions of southern Britain in the 1st century BC. Abandoned forts were sometimes reoccupied and refortified under renewed threat of foreign invasion, such as the Dukes' Wars in Lithuania, the successive invasions of Britain by Romans and Vikings. Excavations at hillforts in the first half of the 20th century focussed on the defenses, based on the assumption that hillforts were developed for military purposes; the exception to this trend began in the 1930s with a series of excavations undertaken by Mortimer Wheeler at Maiden Castle, Dorset. From 1960 onwards, archaeologists shifted their attention to the interior of hillforts, re-examining their function.
Post-processual archaeologists regard hillforts as symbols of wealth and power. Michael Avery has stated the traditional view of hillforts by saying, "The ultimate defensive weapon of European prehistory was the hillfort of the first millennium B. C.". Beyond the simple definition of hillfort, there is a wide variation in types and periods from the Bronze Age to the Middle Ages. Here are some considerations of general appearance and topology, which can be assessed without archaeological excavation: Location Hilltop Contour: the classic hillfort. Examples: Brent Knoll, Mount Ipf. Inland Promontory: an inland defensive position on a ridge or spur with steep slopes on 2 or 3 sides, artificial ramparts on the level approaches. Example: Lambert's Castle. Interfluvial: a promontory above the confluence of two rivers, or in the bend of a meander. Examples: Kelheim, Miholjanec. Lowland: an inland location without special defensive advantages, but surrounded by artificial ramparts. Examples: Maiden Castle, Old Oswestry, Stonea Camp.
Sea Cliff: a semi-circular crescent of ramparts backing on to a straight sea cliff. Examples: Daw's Castle, Dinas Dinlle, Dún Aengus. Sea Promontory: a linear earthwork across a narrow neck of land leading to a peninsula with steep cliffs to the sea on three sides. Examples: Huelgoat. Sloping Enclosure or Hill-slope enclosure: smaller earthwork on sloping hillsides. Examples: Goosehill Camp, Plainsfield Camp, Trendle Ring. Area > 20 ha: large enclosures, too diffuse to defend used for domesticated animals. Example: Bindon Hill. 1–20 ha: defended areas large enough to support permanent tribal settlement. Example: Scratchbury Camp < 1 ha: small enclosures, more to be individual farmsteads or animal pens. Example: Trendle Ring. Ramparts and ditches Univallate: a single circuit of ramparts for enclosure and defence. Example: Solsbury Hill. Bivallate: a double circuit of defensive earthworks. Example: Battlesbury Camp. Multivallate: more than one layer of defensive earthworks, outer works might not be complet
The Bronze Age is a historical period characterized by the use of bronze, in some areas proto-writing, other early features of urban civilization. The Bronze Age is the second principal period of the three-age Stone-Bronze-Iron system, as proposed in modern times by Christian Jürgensen Thomsen, for classifying and studying ancient societies. An ancient civilization is defined to be in the Bronze Age either by producing bronze by smelting its own copper and alloying with tin, arsenic, or other metals, or by trading for bronze from production areas elsewhere. Bronze itself is harder and more durable than other metals available at the time, allowing Bronze Age civilizations to gain a technological advantage. Copper-tin ores are rare, as reflected in the fact that there were no tin bronzes in Western Asia before trading in bronze began in the third millennium BC. Worldwide, the Bronze Age followed the Neolithic period, with the Chalcolithic serving as a transition. Although the Iron Age followed the Bronze Age, in some areas, the Iron Age intruded directly on the Neolithic.
Bronze Age cultures differed in their development of the first writing. According to archaeological evidence, cultures in Mesopotamia and Egypt developed the earliest viable writing systems; the overall period is characterized by widespread use of bronze, though the place and time of the introduction and development of bronze technology were not universally synchronous. Human-made tin bronze technology requires set production techniques. Tin must be mined and smelted separately added to molten copper to make bronze alloy; the Bronze Age was a time of developing trade networks. A 2013 report suggests that the earliest tin-alloy bronze dates to the mid-5th millennium BC in a Vinča culture site in Pločnik, although this culture is not conventionally considered part of the Bronze Age; the dating of the foil has been disputed. Western Asia and the Near East was the first region to enter the Bronze Age, which began with the rise of the Mesopotamian civilization of Sumer in the mid 4th millennium BC.
Cultures in the ancient Near East practiced intensive year-round agriculture, developed a writing system, invented the potter's wheel, created a centralized government, written law codes and nation states and empires, embarked on advanced architectural projects, introduced social stratification and civil administration and practiced organized warfare and religion. Societies in the region laid the foundations for astronomy and astrology. Dates are approximate, consult particular article for details The Ancient Near East Bronze Age can be divided as following: The Hittite Empire was established in Hattusa in northern Anatolia from the 18th century BC. In the 14th century BC, the Hittite Kingdom was at its height, encompassing central Anatolia, southwestern Syria as far as Ugarit, upper Mesopotamia. After 1180 BC, amid general turmoil in the Levant conjectured to have been associated with the sudden arrival of the Sea Peoples, the kingdom disintegrated into several independent "Neo-Hittite" city-states, some of which survived until as late as the 8th century BC.
Arzawa in Western Anatolia during the second half of the second millennium BC extended along southern Anatolia in a belt that reaches from near the Turkish Lakes Region to the Aegean coast. Arzawa was the western neighbor – sometimes a rival and sometimes a vassal – of the Middle and New Hittite Kingdoms; the Assuwa league was a confederation of states in western Anatolia, defeated by the Hittites under an earlier Tudhaliya I, around 1400 BC. Arzawa has been associated with the much more obscure Assuwa located to its north, it bordered it, may be an alternative term for it. In Ancient Egypt the Bronze Age begins in the Protodynastic period, c. 3150 BC. The archaic early Bronze Age of Egypt, known as the Early Dynastic Period of Egypt follows the unification of Lower and Upper Egypt, c. 3100 BC. It is taken to include the First and Second Dynasties, lasting from the Protodynastic Period of Egypt until about 2686 BC, or the beginning of the Old Kingdom. With the First Dynasty, the capital moved from Abydos to Memphis with a unified Egypt ruled by an Egyptian god-king.
Abydos remained the major holy land in the south. The hallmarks of ancient Egyptian civilization, such as art and many aspects of religion, took shape during the Early Dynastic period. Memphis in the Early Bronze Age was the largest city of the time; the Old Kingdom of the regional Bronze Age is the name given to the period in the 3rd millennium BC when Egypt attained its first continuous peak of civilization in complexity and achievement – the first of three "Kingdom" periods, which mark the high points of civilization in the lower Nile Valley. The First Intermediate Period of Egypt described as a "dark period" in ancient Egyptian history, spanned about 100 years after the end of the Old Kingdom from about 2181 to 2055 BC. Little monumental evidence survives from this period from the early part of it; the First Intermediate Period was a dynamic time when the rule of Egypt was divided between two competing power bases: Heracleopolis in Lower Egypt and Thebes in Upper Egypt. These two kingdoms would come into conflict, with the Theban kings conquering the north, resulting in the reunification of Egypt under a single ruler during the second part of the 11th Dynasty.
The Middle Kingdom of Egypt laste
In topography, prominence measures the height of a mountain or hill's summit relative to the lowest contour line encircling it but containing no higher summit within it. It is a measure of the independence of a summit. A peak's key col is a unique point on this contour line and the parent peak is some higher mountain, selected according to various objective criteria. There are at least two definitions of prominence: The prominence of a peak is the minimum height necessary to descend to get from the summit to any higher terrain, which can be calculated for a given peak in the following way: for every path connecting the peak to higher terrain, find the lowest point on the path. See Figure 1; the prominence of a peak is the height of the peak’s summit above the lowest contour line encircling it but containing no higher summit within it. This allows the prominence of points like Everest to be calculated, as long as a lowest point can be defined; the following mental exercise may illustrate the meaning of topographic prominence.
Imagine a peak and imagine that an imaginary sea level rises to the peak. Now lower the imaginary sea level and an imaginary island appears beneath your feet; the island will merge with other islands that emerge. The island will touch an island with a higher peak than the initial island The summit of that island is the parent peak of the summit, the point at which the two islands touch is the key col of the summit, the elevation rise from the key col to the summit is the topographic prominence of the summit; the parent peak may be either far from the subject peak. The summit of Mount Everest is the parent peak of Aconcagua at a distance of 17,755 km, as well as the parent of the South Summit of Mount Everest at a distance of 360 m; the key col may be close to the subject peak or far from it. The key col for Aconcagua, if sea level is disregarded, is the Bering Strait at a distance of 13,655 km; the key col for the South Summit of Mount Everest is about 100 m distant. Prominence is interesting to many mountaineers because it is an objective measurement, correlated with the subjective significance of a summit.
Peaks with low prominence are either subsidiary tops of some higher summit or insignificant independent summits. Peaks with high prominence tend to be the highest points around and are to have extraordinary views. Only summits with a sufficient degree of prominence are regarded as independent mountains. For example, the world's second-highest mountain is K2. While Mount Everest's South Summit is taller than K2, it is not considered an independent mountain because it is a sub-summit of the main summit. Many lists of mountains take topographic prominence as cutoff. John and Anne Nuttall's The Mountains of England and Wales uses a cutoff of 15 m, Alan Dawson's list of Marilyns uses 150 m.. In the contiguous United States, the famous list of "fourteeners" uses a cutoff of 300 ft / 91 m. In the U. S. 2000 ft of prominence has become an informal threshold that signifies that a peak has major stature. Lists with a high topographic prominence cutoff tend to favor isolated peaks or those that are the highest point of their massif.
While the use of prominence as a cutoff to form a list of peaks ranked by elevation is standard and is the most common use of the concept, it is possible to use prominence as a mountain measure in itself. This generates lists of peaks ranked by prominence, which are qualitatively different from lists ranked by elevation; such lists tend to emphasize isolated high peaks, such as range or island high points and stratovolcanoes. One advantage of a prominence-ranked list is that it needs no cutoff since a peak with high prominence is automatically an independent peak, it is common to define a peak's parent as a particular peak in the higher terrain connected to the peak by the key col. If there are many higher peaks there are various ways of defining which one is the parent, not based on geological or geomorphological factors; the "parent" relationship defines a hierarchy. For example, in Figure 1, the middle peak is a subpeak of the right peak, in turn a subpeak of the left peak, the highest point on its landmass.
In that example, there is no controversy over the hierarchy. These different definitions follow. A special case occurs for the highest point on an oceanic continent; some sources define no parent in this case. Called prominence island parentage, this is defined as follows. In figure 2 the key col of peak A is at the meeting place of two closed contours, one encircling A and the other containing at least one higher peak; the encirclement parent of A is the highest peak, inside this other contour. In terms of the
Geographic coordinate system
A geographic coordinate system is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position and two or three of the numbers represent a horizontal position. A common choice of coordinates is latitude and elevation. To specify a location on a plane requires a map projection; the invention of a geographic coordinate system is credited to Eratosthenes of Cyrene, who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC. A century Hipparchus of Nicaea improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of lunar eclipses, rather than dead reckoning. In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, measured north or south of the island of Rhodes off Asia Minor.
Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day. Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. After their work was translated into Arabic in the 9th century, Al-Khwārizmī's Book of the Description of the Earth corrected Marinus' and Ptolemy's errors regarding the length of the Mediterranean Sea, causing medieval Arabic cartography to use a prime meridian around 10° east of Ptolemy's line. Mathematical cartography resumed in Europe following Maximus Planudes' recovery of Ptolemy's text a little before 1300. In 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, England as the zero-reference line; the Dominican Republic voted against the motion, while Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911.
In order to be unambiguous about the direction of "vertical" and the "horizontal" surface above which they are measuring, map-makers choose a reference ellipsoid with a given origin and orientation that best fits their need for the area they are mapping. They choose the most appropriate mapping of the spherical coordinate system onto that ellipsoid, called a terrestrial reference system or geodetic datum. Datums may be global, meaning that they represent the whole Earth, or they may be local, meaning that they represent an ellipsoid best-fit to only a portion of the Earth. Points on the Earth's surface move relative to each other due to continental plate motion and diurnal Earth tidal movement caused by the Moon and the Sun; this daily movement can be as much as a metre. Continental movement can be up to 10 m in a century. A weather system high-pressure area can cause a sinking of 5 mm. Scandinavia is rising by 1 cm a year as a result of the melting of the ice sheets of the last ice age, but neighbouring Scotland is rising by only 0.2 cm.
These changes are insignificant if a local datum is used, but are statistically significant if a global datum is used. Examples of global datums include World Geodetic System, the default datum used for the Global Positioning System, the International Terrestrial Reference Frame, used for estimating continental drift and crustal deformation; the distance to Earth's center can be used both for deep positions and for positions in space. Local datums chosen by a national cartographical organisation include the North American Datum, the European ED50, the British OSGB36. Given a location, the datum provides the latitude ϕ and longitude λ. In the United Kingdom there are three common latitude and height systems in use. WGS 84 differs at Greenwich from the one used on published maps OSGB36 by 112 m; the military system ED50, used by NATO, differs from about 120 m to 180 m. The latitude and longitude on a map made against a local datum may not be the same as one obtained from a GPS receiver. Coordinates from the mapping system can sometimes be changed into another datum using a simple translation.
For example, to convert from ETRF89 to the Irish Grid add 49 metres to the east, subtract 23.4 metres from the north. More one datum is changed into any other datum using a process called Helmert transformations; this involves converting the spherical coordinates into Cartesian coordinates and applying a seven parameter transformation, converting back. In popular GIS software, data projected in latitude/longitude is represented as a Geographic Coordinate System. For example, data in latitude/longitude if the datum is the North American Datum of 1983 is denoted by'GCS North American 1983'; the "latitude" of a point on Earth's surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the Equator and to each other; the North Pole is 90° N. The 0° parallel of latitude is designated the Equator, the fun
Long barrows known as chambered tombs, were a style of monument constructed across Western Europe in the fifth and fourth millennia BCE, during the Early Neolithic period. Constructed from earth and either timber or stone, those using the latter material represent the oldest widespread tradition of stone construction in the world; the long barrows consist of an earthen tumulus, or "barrow", sometimes with a timber or stone chamber in one end. These monuments contained human remains interred within their chambers, as a result, are interpreted as tombs, although there are some examples where this appears not to have happened; the choice of whether to use timber or stone may have had more to do with the availability of local materials than any cultural differences. The earliest examples developed in Iberia and western France during the mid-fifth millennium BCE; the tradition spread northwards, into the British Isles and the Low Countries and Southern Scandinavia. Each area developed its own regional variations of the long barrow tradition exhibiting their own architectural innovations.
The purpose and meaning of such barrows remains an issue of debate among archaeologists. One argument is that they are religious sites erected as part of a system of ancestor veneration or as a religion spread by missionaries or settlers. An alternative explanation views them in economic terms, as territorial markers delineating the areas controlled by different communities as they transitioned toward farming. Around 40,000 chambered long barrows survive today. Many have been excavated by archaeologists. Given their dispersal across Western Europe, long barrows have been given different names in the various different languages of this region; the term "barrow" is a southern English dialect word for an earthen tumulus, was adopted as a scholarly term for such monuments by the 17th century English antiquarian John Aubrey. Synonyms found in other parts of Britain included low in Cheshire and Derbyshire, tump in Gloucestershire and Hereford, howe in Northern England and Scotland, cairn in Scotland.
Another term to have achieved international usage has been "dolmen", a Breton word meaning "table-stone". The historian Ronald Hutton suggested that such sites could be termed "tomb-shrines" to reflect the fact that they appear to have been used both to house the remains of the dead and to have been used in ritualised activities; the decision as to whether a long barrow used wood or stone appears to have been based on the availability of resources. Some of the long barrows contained stone-lined chambers within them. Early 20th century archaeologists began to call these monuments chambered tombs; the archaeologists Roy and Lesley Adkins referred to these monuments as megalithic long barrows. In most cases, local stone was used; the style of the chamber falls into two categories. One form, known as grottes sepulchrales artificielles in French archaeology, are dug into the earth; the second form, more widespread, are known as cryptes dolmeniques in French archaeology and involved the chamber being erected above ground.
Many chambered long barrows contained side chambers within them producing a cruciform shape. Others had no such side alcoves; the term earthen long barrow was coined by the British archaeologist Stuart Piggott. These long barrows might have used timber; the construction of long barrows in the Early Neolithic would have required the co-operation of a number of different individuals and would have represented an important investment in time and resources. Many were restyled over their long period of use. Ascertaining at what date a chambered long barrow was constructed is difficult for archaeologists as a result of the various modifications that were made to the monument during the Early Neolithic. Both modifications and damage can make it difficult to determine the nature of the original long barrow design. Enviro-archaeological studies have demonstrated that many of the long barrows were erected in wooded landscapes. In Britain, these chambered long barrows are located on prominent hills and slopes, in particular being located above rivers and inlets and overlooking valleys.
In Britain, long barrows were often constructed near to causewayed enclosures, a form of earthen monument. Across Europe, about 40,000 long barrows are known to survive from the Early Neolithic, they are found across much of Western Europe. The long barrows are not the world's oldest known structures using stone—they are predated by Göbekli Tepe in modern Turkey—but they do represent the oldest widespread tradition of using stone in construction; the archaeologist Frances Lynch has described them as "the oldest built structures in Europe" to survive. Although found across this large area, they can be subdivided into clear regionalised traditions based on architectural differences. Excavation has revealed that some of the long barrows in the area of modern Spain and western France were erected in the mid-fifth millennium BCE, making these older than those long barrows further north. Although the general area in which the oldest long barrows were built is therefore known, archaeologists do not know where the tradition started nor which long barrows are the first ones to have been built.
It therefore appears that the architectural tradition developed in this southern area of Western Europe before spreading north