1.
Atlantic Ocean
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The Atlantic Ocean is the second largest of the worlds oceans with a total area of about 106,460,000 square kilometres. It covers approximately 20 percent of the Earths surface and about 29 percent of its surface area. It separates the Old World from the New World, the Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. The Equatorial Counter Current subdivides it into the North Atlantic Ocean, in contrast, the term Atlantic originally referred specifically to the Atlas Mountains in Morocco and the sea off the Strait of Gibraltar and the North African coast. The Greek word thalassa has been reused by scientists for the huge Panthalassa ocean that surrounded the supercontinent Pangaea hundreds of years ago. The term Aethiopian Ocean, derived from Ancient Ethiopia, was applied to the Southern Atlantic as late as the mid-19th century, many Irish or British people refer to the United States and Canada as across the pond, and vice versa. The Black Atlantic refers to the role of ocean in shaping black peoples history. Irish migration to the US is meant when the term The Green Atlantic is used, the term Red Atlantic has been used in reference to the Marxian concept of an Atlantic working class, as well as to the Atlantic experience of indigenous Americans. Correspondingly, the extent and number of oceans and seas varies, the Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Strait, Greenland Sea, Norwegian Sea, to the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltar and Africa. In the southeast, the Atlantic merges into the Indian Ocean, the 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. In the 1953 definition it extends south to Antarctica, while in later maps it is bounded at the 60° parallel by the Southern Ocean, the Atlantic has irregular coasts indented by numerous bays, gulfs, and seas. Including these marginal seas the coast line of the Atlantic measures 111,866 km compared to 135,663 km for the Pacific. Including its marginal seas, the Atlantic covers an area of 106,460,000 km2 or 23. 5% of the ocean and has a volume of 310,410,900 km3 or 23. 3%. Excluding its marginal seas, the Atlantic covers 81,760,000 km2 and has a volume of 305,811,900 km3, the North Atlantic covers 41,490,000 km2 and the South Atlantic 40,270,000 km2. The average depth is 3,646 m and the maximum depth, the bathymetry of the Atlantic is dominated by a submarine mountain range called the Mid-Atlantic Ridge. It runs from 87°N or 300 km south of the North Pole to the subantarctic Bouvet Island at 42°S, the MAR divides the Atlantic longitudinally into two halves, in each of which a series of basins are delimited by secondary, transverse ridges. The MAR reaches above 2000 m along most of its length, the MAR is a barrier for bottom water, but at these two transform faults deep water currents can pass from one side to the other
2.
Columbia University
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Columbia University is a private Ivy League research university in Upper Manhattan, New York City. It was established in 1754 as Kings College by royal charter of George II of Great Britain, after the American Revolutionary War, Kings College briefly became a state entity, and was renamed Columbia College in 1784. Columbia is one of the fourteen founding members of the Association of American Universities and was the first school in the United States to grant the M. D. degree. The university also has global research outposts in Amman, Beijing, Istanbul, Paris, Mumbai, Rio de Janeiro, Santiago, Asunción, Columbia administers annually the Pulitzer Prize. Additionally,100 Nobel laureates have been affiliated with Columbia as students, researchers, faculty, Columbia is second only to Harvard University in the number of Nobel Prize-winning affiliates, with over 100 recipients of the award as of 2016. In 1746 an act was passed by the assembly of New York to raise funds for the foundation of a new college. Classes were initially held in July 1754 and were presided over by the colleges first president, Dr. Johnson was the only instructor of the colleges first class, which consisted of a mere eight students. Instruction was held in a new schoolhouse adjoining Trinity Church, located on what is now lower Broadway in Manhattan, in 1763, Dr. Johnson was succeeded in the presidency by Myles Cooper, a graduate of The Queens College, Oxford, and an ardent Tory. In the charged political climate of the American Revolution, his opponent in discussions at the college was an undergraduate of the class of 1777. The suspension continued through the occupation of New York City by British troops until their departure in 1783. The colleges library was looted and its sole building requisitioned for use as a hospital first by American. Loyalists were forced to abandon their Kings College in New York, the Loyalists, led by Bishop Charles Inglis fled to Windsor, Nova Scotia, where they founded Kings Collegiate School. After the Revolution, the college turned to the State of New York in order to restore its vitality, the Legislature agreed to assist the college, and on May 1,1784, it passed an Act for granting certain privileges to the College heretofore called Kings College. The Regents finally became aware of the colleges defective constitution in February 1787 and appointed a revision committee, in April of that same year, a new charter was adopted for the college, still in use today, granting power to a private board of 24 Trustees. On May 21,1787, William Samuel Johnson, the son of Dr. Samuel Johnson, was unanimously elected President of Columbia College, prior to serving at the university, Johnson had participated in the First Continental Congress and been chosen as a delegate to the Constitutional Convention. The colleges enrollment, structure, and academics stagnated for the majority of the 19th century, with many of the college presidents doing little to change the way that the college functioned. In 1857, the college moved from the Kings College campus at Park Place to a primarily Gothic Revival campus on 49th Street and Madison Avenue, during the last half of the 19th century, under the leadership of President F. A. P. Barnard, the institution assumed the shape of a modern university
3.
Ice core
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An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. As the ice forms from the buildup of annual layers of snow, lower layers are older than upper. The properties of the ice and the recrystallized inclusions within the ice can then be used to reconstruct a record over the age range of the core. This enables the reconstruction of local records and the history of atmospheric composition. Ice cores contain an abundance of information about climate, inclusions in the snow of each year remain in the ice, such as wind-blown dust, ash, pollen, bubbles of atmospheric gas and radioactive substances. The variety of climatic proxies is greater than in any other natural recorder of climate, the length of the record depends on the depth of the ice core and varies from a few years up to 800 kyr for the EPICA core. The time resolution depends on the amount of snowfall. Upper layers of ice in a core correspond to a year or sometimes a single season. Deeper into the ice the layers thin and annual layers become indistinguishable and it is the simultaneity of these properties recorded in the ice that makes ice cores such a powerful tool in paleoclimate research. Ice sheets are formed from snow, because an ice sheet survives summer, the temperature in that location usually does not warm much above freezing. In many locations in Antarctica the air temperature is well below the freezing point of water. If the summer temperatures do get above freezing, any ice core record will be degraded or completely useless. The surface layer is snow in various forms, with air gaps between snowflakes, as snow continues to accumulate, the buried snow is compressed and forms firn, a grainy material with a texture similar to granulated sugar. Air gaps remain, and some circulation of air continues, as snow accumulates above, the firn continues to densify, and at some point the pores close off and the air is trapped. Because the air continues to circulate until then, the ice age and the age of the gas enclosed are not the same, the gas age–ice age difference is as great as 7 kyr in glacial ice from Vostok. Under increasing pressure, at depth the firn is compressed into ice. This depth may range between a few to tens of meters to typically 100 m for Antarctic cores. Below this level material is frozen in the ice, Ice may appear clear or blue
4.
Asia
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Asia covers an area of 44,579,000 square kilometres, about 30% of Earths total land area and 8. 7% of the Earths total surface area. The continent, which has long been home to the majority of the population, was the site of many of the first civilizations. Asia is notable for not only its large size and population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, the western boundary with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. The most commonly accepted boundaries place Asia to the east of the Suez Canal, the Ural River, and the Ural Mountains, and south of the Caucasus Mountains, China and India alternated in being the largest economies in the world from 1 to 1800 A. D. The accidental discovery of America by Columbus in search for India demonstrates this deep fascination, the Silk Road became the main East-West trading route in the Asian hitherland while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may actually have more to do with human geography than physical geography. Asia varies greatly across and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties, the boundary between Asia and Africa is the Red Sea, the Gulf of Suez, and the Suez Canal. This makes Egypt a transcontinental country, with the Sinai peninsula in Asia, the border between Asia and Europe was historically defined by European academics. In Sweden, five years after Peters death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Urals as the border of Asia, the Russians were enthusiastic about the concept, which allowed them to keep their European identity in geography. Tatishchev announced that he had proposed the idea to von Strahlenberg, the latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century, the border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is usually placed along the crest of the Caucasus Mountains, the border between Asia and the loosely defined region of Oceania is usually placed somewhere in the Malay Archipelago. The terms Southeast Asia and Oceania, devised in the 19th century, have had several different geographic meanings since their inception. The chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the possessions of the various empires there. Lewis and Wigen assert, The narrowing of Southeast Asia to its present boundaries was thus a gradual process, Asia is larger and more culturally diverse than Europe. It does not exactly correspond to the borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system on the grounds there is no or is no substantial physical separation between them
5.
Monsoon
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Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes used for locally heavy but short-term rains. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons, the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The south-west monsoon winds are called Nairutya Maarut in India, the English monsoon came from Portuguese monção, ultimately from Arabic mawsim and/or Hindi mausam, perhaps partly via early modern Dutch monsun. Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to climate change. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago, then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean and it is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma,1.83 Ma,0.68 Ma,0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. The impact of monsoon on the weather is different from place to place. In some places there is just a likelihood of having a more or less rain. In other places, quasi semi-deserts are turned into green grasslands where all sorts of plants. The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands, see photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways, in contrast, dirt, sand, and rocks have lower heat capacities, and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at an even temperature
6.
Middle East
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The Middle East is a transcontinental region centered on Western Asia and Egypt. The corresponding adjective is Middle-Eastern and the noun is Middle-Easterner. The term has come into usage as a replacement of the term Near East beginning in the early 20th century. Arabs, Turks, Persians, Kurds, and Azeris constitute the largest ethnic groups in the region by population. Indigenous minorities of the Middle East include Jews, Assyrians and other Arameans, Baloch, Berbers, Copts, Druze, Lurs, Mandaeans, Samaritans, Shabaks, Tats, in the Middle East, there is also a Romani community. European ethnic groups form a diaspora in the region include Albanians, Bosniaks, Circassians, Crimean Tatars, Franco-Levantines. Among other migrant populations are Bengalis as well as other Indians, Chinese, Filipinos, Indonesians, Pakistanis, the history of the Middle East dates back to ancient times, with the importance of the region being recognized for millennia. Most of the countries border the Persian Gulf have vast reserves of crude oil. The term Middle East may have originated in the 1850s in the British India Office, however, it became more widely known when American naval strategist Alfred Thayer Mahan used the term in 1902 to designate the area between Arabia and India. During this time the British and Russian Empires were vying for influence in Central Asia, Mahan realized not only the strategic importance of the region, but also of its center, the Persian Gulf. Mahan first used the term in his article The Persian Gulf and International Relations, published in September 1902 in the National Review, a British journal. The Middle East, if I may adopt a term which I have not seen, will some day need its Malta, as well as its Gibraltar, it does not follow that either will be in the Persian Gulf. The British Navy should have the facility to concentrate in force if occasion arise, about Aden, India, mahans article was reprinted in The Times and followed in October by a 20-article series entitled The Middle Eastern Question, written by Sir Ignatius Valentine Chirol. During this series, Sir Ignatius expanded the definition of Middle East to include regions of Asia which extend to the borders of India or command the approaches to India. After the series ended in 1903, The Times removed quotation marks from subsequent uses of the term, in the late 1930s, the British established the Middle East Command, which was based in Cairo, for its military forces in the region. After that time, the term Middle East gained broader usage in Europe, the description Middle has also led to some confusion over changing definitions. Before the First World War, Near East was used in English to refer to the Balkans and the Ottoman Empire, while Middle East referred to Iran, the Caucasus, Afghanistan, Central Asia, and Turkestan. The first official use of the term Middle East by the United States government was in the 1957 Eisenhower Doctrine, the Associated Press Stylebook says that Near East formerly referred to the farther west countries while Middle East referred to the eastern ones, but that now they are synonymous
7.
Akkadian Empire
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The empire united all the Akkadian and Sumerian speakers under one rule. The Akkadian Empire controlled Mesopotamia, the Levant, and eastern and southern parts of Anatolia and Iran, sending military expeditions as far south as Dilmun and Magan in the Arabian Peninsula. During the 3rd millennium BC, there developed an intimate cultural symbiosis between the Sumerians and the Akkadians, which included widespread bilingualism. Akkadian gradually replaced Sumerian as a spoken language somewhere between the 3rd and the 2nd millennia BC, the Akkadian Empire reached its political peak between the 24th and 22nd centuries BC, following the conquests by its founder Sargon of Akkad. Under Sargon and his successors, the Akkadian language was imposed on neighboring conquered states such as Elam. Akkad is sometimes regarded as the first empire in history, though there are earlier Sumerian claimants, the Bible refers to Akkad in Genesis 10,10, which states that the beginning of Nimrods kingdom was in the land of Akkad. Nimrod is a Hebrew name not attested in Mesopotamians sources, many have pointed out similarities with the legend of Gilgamesh who founded Uruk, which is said to be the city Nimrod came to power. Today, some 7,000 texts from the Akkadian period alone are known, many later texts from the successor states of Assyria and Babylonia also deal with the Akkadian Empire. Understanding of the Akkadian Empire continues to be hampered by the fact that its capital Akkad has not yet been located, likewise, material that is thought to be Akkadian continues to be in use into the Ur III period. Many of the recent insights on the Akkadian Empire have come from excavations in the Upper Khabur area in modern northeastern Syria which was to become a part of Assyria after the fall of Akkad. For example, excavations at Tell Mozan brought to light a sealing of Taram-Agade, an unknown daughter of Naram-Sin. The excavators at nearby Tell Leilan have used the results from their investigations to argue that the Akkadian Empire came to an end due to a sudden drought, the so-called 4.2 kiloyear event. The impact of this event on Mesopotamia in general, and on the Akkadian Empire in particular. The Akkadian Period is contemporary with, EB IV, EB IVA and EJ IV, the absolute dates of their reigns are approximate. The Akkadian Empire takes its name from the region and city of Akkad, although the city of Akkad has not yet been identified on the ground, it is known from various textual sources. Among these is at least one text predating the reign of Sargon, together with the fact that the name Akkad is of non-Akkadian origin, this suggests that the city of Akkad may have already been occupied in pre-Sargonic times. Sargon of Akkad defeated and captured Lugal-Zage-Si in the Battle of Uruk, the earliest records in the Akkadian language date to the time of Sargon. Sargon was claimed to be the son of Laibum or Itti-Bel, a humble gardener, One legend related of Sargon in Assyrian times says that My mother was a changeling, my father I knew not
8.
Old Kingdom of Egypt
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The term itself was coined by eighteenth-century historians and the distinction between the Old Kingdom and the Early Dynastic Period is not one which would have been recognized by Ancient Egyptians. The Old Kingdom is most commonly regarded as the period from the Third Dynasty through to the Sixth Dynasty, many Egyptologists also include the Memphite Seventh and Eighth Dynasties in the Old Kingdom as a continuation of the administration centralized at Memphis. During the Old Kingdom, the king of Egypt became a god who ruled absolutely and could demand the services. Under King Djoser, the first king of the Third Dynasty of the Old Kingdom, the capital of Egypt was moved to Memphis. A new era of building was initiated at Saqqara under his reign, King Djosers architect, Imhotep is credited with the development of building with stone and with the conception of the new architectural form—the Step Pyramid. Indeed, the Old Kingdom is perhaps best known for the number of pyramids constructed at this time as burial places for Egypts kings. For this reason, the Old Kingdom is frequently referred to as the Age of the Pyramids, the first king of the Old Kingdom was Djoser of the third dynasty, who ordered the construction of a pyramid in Memphis necropolis, Saqqara. An important person during the reign of Djoser was his vizier and it was in this era that formerly independent ancient Egyptian states became known as nomes, under the rule of the king. The former rulers were forced to assume the role of governors or otherwise work in tax collection, Egyptians in this era worshipped their king as a god, believing that he ensured the annual flooding of the Nile that was necessary for their crops. Egyptian views on the nature of time during this period held that the worked in cycles. They also perceived themselves as a specially selected people, the Old Kingdom and its royal power reached a zenith under the Fourth Dynasty, which began with Sneferu. Using more stones than any king, he built three pyramids, a now collapsed pyramid in Meidum, the Bent Pyramid at Dahshur. However, the development of the pyramid style of building was reached not at Saqqara. Sneferu was succeeded by his son, Khufu who built the Great Pyramid of Giza, after Khufus death, his sons Djedefra and Khafra may have quarrelled. The latter built the pyramid and the Sphinx in Giza. Recent reexamination of evidence has led Egyptologist Vassil Dobrev to propose that the Sphinx had been built by Djedefra as a monument to his father Khufu, alternatively, the Sphinx has been proposed to be the work of Khafra and Khufu himself. There were military expeditions into Canaan and Nubia, with Egyptian influence reaching up the Nile into what is today the Sudan, the later kings of the Fourth Dynasty were king Menkaure, who built the smallest pyramid in Giza, Shepseskaf and, perhaps, Djedefptah. The Fifth Dynasty began with Userkaf and was marked by the importance of the cult of sun god Ra
9.
Glacier
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A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs and they also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia also have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue. The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
10.
Norway
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The Antarctic Peter I Island and the sub-Antarctic Bouvet Island are dependent territories and thus not considered part of the Kingdom. Norway also lays claim to a section of Antarctica known as Queen Maud Land, until 1814, the kingdom included the Faroe Islands, Greenland, and Iceland. It also included Isle of Man until 1266, Shetland and Orkney until 1468, Norway has a total area of 385,252 square kilometres and a population of 5,258,317. The country shares a long border with Sweden. Norway is bordered by Finland and Russia to the north-east, Norway has an extensive coastline, facing the North Atlantic Ocean and the Barents Sea. King Harald V of the Dano-German House of Glücksburg is the current King of Norway, erna Solberg became Prime Minister in 2013, replacing Jens Stoltenberg. A constitutional monarchy, Norway divides state power between the Parliament, the Cabinet and the Supreme Court, as determined by the 1814 Constitution, the kingdom is established as a merger of several petty kingdoms. By the traditional count from the year 872, the kingdom has existed continuously for 1,144 years, Norway has both administrative and political subdivisions on two levels, counties and municipalities. The Sámi people have an amount of self-determination and influence over traditional territories through the Sámi Parliament. Norway maintains close ties with the European Union and the United States, the country maintains a combination of market economy and a Nordic welfare model with universal health care and a comprehensive social security system. Norway has extensive reserves of petroleum, natural gas, minerals, lumber, seafood, the petroleum industry accounts for around a quarter of the countrys gross domestic product. On a per-capita basis, Norway is the worlds largest producer of oil, the country has the fourth-highest per capita income in the world on the World Bank and IMF lists. On the CIAs GDP per capita list which includes territories and some regions, from 2001 to 2006, and then again from 2009 to 2017, Norway had the highest Human Development Index ranking in the world. It also has the highest inequality-adjusted ranking, Norway ranks first on the World Happiness Report, the OECD Better Life Index, the Index of Public Integrity and the Democracy Index. Norway has two names, Noreg in Nynorsk and Norge in Bokmål. The name Norway comes from the Old English word Norðrveg mentioned in 880, meaning way or way leading to the north. In contrasting with suðrvegar southern way for Germany, and austrvegr eastern way for the Baltic, the Anglo-Saxon of Britain also referred to the kingdom of Norway in 880 as Norðmanna land. This was the area of Harald Fairhair, the first king of Norway, and because of him
11.
Boreal (age)
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In peat bog sediments, the Boreal is also recognized by its characteristic pollen zone. It was preceded by the Younger Dryas, the last cold snap of the Pleistocene, and followed by the Atlantic, the Boreal, transitional between the two periods, varied a great deal, at times comprising within it climates like todays. Subsequent to the original Blytt-Sernander scheme, the first stage of the Boreal was divided off as a Pre-boreal transitional phase, some current schemes based on pollen zones also distinguish a pre-Boreal, an early Boreal and a late Boreal. The generally accepted date for the end of the Younger Dryas, the start of the period is relatively sharply defined by a rise of 7 °C in 50 years. The date is based fairly solidly on Greenland ice cores, which give 11,640 BP for the late Younger Dryas and 11,400 BP for the early Pre-Boreal, but estimates of other dates vary by up to 1000 years, for a number of reasons. First, Boreal can identify a paleoclimate, a zone or a temporally-fixed chronozone. Second, different dating methods obtain different dates, the underlying problem is that climate and pollen vary somewhat from region to region. The scientists of each use the methods available in their region, whether lake varves. Standardization has become of increasing concern to scientists everywhere, dates from many methods continue to multiply as paleoclimatologists seek higher resolution. But it is unclear whether regional variation will allow high-resolution standardization, yet, there are some solid dates of the Pre-Boreal and Boreal. The Saksunarvatn tephra is dated in Greenland ice to 10, 180±60 BP, in deposits at Krakenes in Norway, to 10, 010–9,980 years BP calibrated, in northwest German lakes. The tephra occurs in early Boreal contexts, so, it seems certain that the early Boreal includes the year 10,000 BP. Similarly, the late Boreal includes the Kilian/Vasset tephra of Swiss and southwest German lakes at 8200 BP, but the borders are less certain. Studies of bogs in northwest Russia are the basis for a division of the PreBoreal into PB-1,10, 000-9800, the scheme goes on to divide the Boreal into BO-1, 9300–9000, BO-2, 9000–8500, and BO-3, 8500–8000, incal. CalPal used on these dates suggests overall boundaries of 11,500 and 10,500 BP for the Pre-Boreal, dates given recently are usually earlier than those given more than 10 years ago. For example, Iverson and Rud give dates of 10, 000–9000 BP for the PreBoreal and 9000–8000 BP for the Boreal, presumably, more-recent dates are more accurate, as technology improves with time, often quite rapidly. Yet, pollen and climate phases also to some degree may depend on latitude, scientists look for the overall pattern of the dates, but that technique is not 100% reliable, either. Large numbers of herbivores wandered in herds over vast distances, the blanket teemed with small, rapidly reproducing species, which supported food chains of larger predators
. PMID 18772385.
