Younger Dryas in the context of "Green Sahara"

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⭐ Core Definition: Younger Dryas

The Younger Dryas (YD, Greenland Stadial GS-1) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP). It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the North Atlantic Ocean cooled and annual air temperatures decreased by ~3 °C (5 °F) over North America, 2–6 °C (4–11 °F) in Europe and up to 10 °C (18 °F) in Greenland, in a few decades. Cooling in Greenland was particularly rapid, taking place over just 3 years or less. At the same time, the Southern Hemisphere experienced warming. This period ended as rapidly as it began, with dramatic warming over ~50 years, the transition from the glacial Pleistocene epoch into the current Holocene.

The Younger Dryas onset was not fully synchronized; in the tropics, the cooling was spread out over several centuries, and the same was true of the early-Holocene warming. Even in the Northern Hemisphere, temperature change was highly seasonal, with much colder winters, cooler springs, yet no change or even slight warming during the summer. Substantial changes in precipitation also took place, with cooler areas experiencing substantially lower rainfall, while warmer areas received more of it. In the Northern Hemisphere, the length of the growing season declined. Land ice cover experienced little net change, but sea ice extent had increased, contributing to ice–albedo feedback. This increase in albedo was the main reason for net global cooling of 0.6 °C (1.1 °F).

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👉 Younger Dryas in the context of Green Sahara

The African humid period (AHP; also known by other names) was a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt, changes in vegetation and dust in the Sahara which strengthened the African monsoon, and increased greenhouse gases.During the preceding Last Glacial Maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously to the Bølling–Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event.

The AHP led to a widespread settlement of the Sahara and the Arabian Desert, and had a profound effect on African cultures, such as the birth of the Ancient Egyptian civilization. People in the Sahara lived as hunter-gatherers and domesticated cattle, goats and sheep. They left archaeological sites and artifacts such as one of the oldest ships in the world, and rock paintings such as those in the Cave of Swimmers and in the Acacus Mountains. Earlier humid periods in Africa were postulated after the discovery of these rock paintings in now-inhospitable parts of the Sahara. When the period ended, humans gradually abandoned the desert in favour of regions with more secure water supplies, such as the Nile Valley and Mesopotamia, where they gave rise to early complex societies.

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Younger Dryas in the context of Late Pleistocene

The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently defined as the time between c. 129,000 and c. 11,700 years ago. The late Pleistocene equates to the proposed Tarantian Age of the geologic time scale, preceded by the officially ratified Chibanian (commonly known as the Middle Pleistocene). The beginning of the Late Pleistocene is the transition between the end of the Penultimate Glacial Period and the beginning of the Last Interglacial around 130,000 years ago (corresponding with the beginning of Marine Isotope Stage 5). The Late Pleistocene ends with the termination of the Younger Dryas, some 11,700 years ago when the Holocene Epoch began.

The term Upper Pleistocene is currently in use as a provisional or "quasi-formal" designation by the International Union of Geological Sciences (IUGS). Although the three oldest ages of the Pleistocene (the Gelasian, the Calabrian and the Chibanian) have been officially defined, the late Pleistocene has yet to be formally defined.

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Younger Dryas in the context of Pre-Pottery Neolithic

The Pre-Pottery Neolithic (PPN) represents the early Neolithic in the Near East, dating to c. 12,000 – c. 8,500 years ago, (10000 – 6500 BCE). It succeeds the Natufian culture of the Epipalaeolithic Near East (also called Mesolithic), as the domestication of plants and animals was in its formative stages, having possibly been induced by the Younger Dryas.

The Pre-Pottery Neolithic culture came to an end around the time of the 8.2-kiloyear event, a cool spell centred on 6200 BCE that lasted several hundred years. It is succeeded by the Pottery Neolithic.

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Younger Dryas in the context of Ice age

An ice age is a term describing periods of time when the reduction in the temperature of Earth's surface and atmosphere results in the presence or expansion of continental and polar ice sheets and alpine glaciers. The term is applied in several different senses to very long and comparatively short periods of cooling. Colder periods are called glacials or ice ages, and warmer periods are called interglacials.

Earth's climate alternates between icehouse and greenhouse periods based on whether there are glaciers on the planet, and for most of Earth's history it has been in a greenhouse period with little or no permanent ice. Over the very long term, Earth is currently in an icehouse period called the Late Cenozoic Ice Age, which started 34 million years ago. There have been colder and warmer periods within this ice age, and the term is also applied to the Quaternary glaciation, which started 2.58 million years ago. Within this period, the Last Interglacial ended 115,000 years ago, and was followed by the Last Glacial Period (LGP), which gave way to the current warm Holocene, which started 11,700 years ago. The most severe cold period of the LGP was the Last Glacial Maximum, which reached its maximum between 26,000 and 20,000 years ago. The most recent glaciation was the Younger Dryas between 12,800 and 11,700 years ago

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Younger Dryas in the context of History of Ireland

The first evidence of human presence in Ireland dates to around 34,000 years ago, with further findings dating the presence of Homo sapiens to 7,000 BC. The receding of the ice the Younger Dryas cold phase of the Quaternary, around 9700 BC, heralds the beginning of Prehistoric Ireland, which includes the archaeological periods known as the Mesolithic, the Neolithic from about 4000 BC, and the Copper Age beginning around 2500 BC with the arrival of the Beaker Culture. The Irish Bronze Age proper begins around 2000 BC and ends with the arrival of the Iron Age of the Celtic Hallstatt culture, beginning about 600 BC. The subsequent La Tène culture brought new styles and practices by 300 BC.

Greek and Roman writers give some information about Ireland during the Classical period (see "protohistoric" period), by which time the island may be termed "Gaelic Ireland". By the late 4th century CE Christianity had begun to gradually subsume or replace the earlier Celtic polytheism. By the end of the 6th century, it had introduced writing along with a predominantly monastic Celtic Christian church, profoundly altering Irish society. Seafaring raiders and pirates from Scandinavia (later referred to as Vikings), settled from the late 8th century AD which resulted in extensive cultural interchange, as well as innovation in military and transport technology. Many of Ireland's towns were founded at this time as Scandinavian trading posts and coinage made its first appearance. Scandinavian penetration was limited and concentrated along coasts and rivers, and ceased to be a major threat to Gaelic culture after the Battle of Clontarf in 1014. The Norman invasion in 1169 resulted again in a partial conquest of the island and marked the beginning of more than 800 years of English political and military involvement in Ireland. Initially successful, Norman gains were rolled back over succeeding centuries as a Gaelic resurgence reestablished Gaelic cultural preeminence over most of the country, apart from the walled towns and the area around Dublin known as The Pale.

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Younger Dryas in the context of 8.2-kiloyear event

In climatology, the 8.2 kiloyear event was a rapid drop in global temperatures that occurred around 8,200 years ago, lasting between two and four centuries. This event marks the beginning of the Northgrippian Age within the Holocene epoch. While this cooling phase was not as intense as the earlier Younger Dryas period that occurred just before the Holocene began, it was still significant. During the 8.2-kiloyear event, atmospheric methane levels dropped by 80 parts per billion, a 15% reduction, suggesting a broad cooling and drying trend across the Northern Hemisphere.

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Younger Dryas in the context of Creswellian

The Creswellian is a British Upper Palaeolithic culture named after the type site of Creswell Crags in Derbyshire by Dorothy Garrod in 1926. It is also known as the British Late Magdalenian. According to Andreas Maier: "In current research, the Creswellian and Hamburgian are considered to be independent but closely related entities which are rooted in the Magdalenian." The Creswellian is dated between 13,000 and 11,800 BP and was followed by the most recent ice age, the Younger Dryas, when Britain was at times unoccupied by humans.

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Younger Dryas in the context of Early Holocene

In the geologic time scale, the Greenlandian is the earliest age or lowest stage of the Holocene Epoch or Series, part of the Quaternary. Beginning in 11,650 BP (9701 BCE or 300 HE) and ending with the 8.2-kiloyear event (c. 8200–8300 BP, 6200–6300 BCE, 3600–3700 HE), it is the earliest of three sub-divisions of the Holocene. It was officially ratified by the International Commission on Stratigraphy in June 2018 with the later Northgrippian and Meghalayan Ages/Stages. The lower boundary of the Greenlandian Age is the GSSP sample from the North Greenland Ice Core Project in central Greenland (75.1000°N 42.3200°W). The Greenlandian GSSP has been correlated with the end of Younger Dryas (from near-glacial to interglacial) and a "shift in lower deuterium excess values".

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Younger Dryas in the context of Muonio

Muonio (previously called Muonionniska; Northern Sami: Muoná) is a municipality of Finland. The town is located in fell-region of far northern Finland above the Arctic Circle on the country's western border with Sweden, the Muonio River. It lies within the area of the former Lappi (Lapland) province in the Fell Lapland subregion. The next closest Finnish municipalities are Enontekiö to the north, Kittilä on the east, and Kolari to the south. Southwest of the town, a road bridge crosses the Muonio River, across the river, in Sweden, lies the nearby hamlet of Muoniovaara ("Muonio hill") in northern Pajala Municipality in Norrbotten County.

The area has been occupied by humans for at least 10,000 years; their arrival is thought to have coincided with deglaciation at the end of the Younger Dryas. They likely arrived from the south or east, since the Scandinavian Mountains rise 2,100 metres on the west, and over 1,300 metres to the north - both form a significant barrier to migration. Remains of eight dwellings from the Middle Stone Age have been excavated on the shore of Lake Akajarvi (fifteen miles from the center of the present-day village).

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