The 8.2 Kiloyear event and pre-pottery neolithic B

[bioblitzkrieg]

8.2 kiloyear event
From Wikipedia, the free encyclopedia

Temperature proxies from ice cores; the 8.2 kyr event can just be seenThe 8.2 kiloyear event is the term that climatologists have adopted for a sudden decrease in global temperatures that occurred approximately 8200 years before the present, or c. 6200 BCE, and which lasted for the next two to four centuries. Milder than the Younger Dryas cold spell that preceded it, but more severe than the Little Ice Age that would follow, the 8.2 kiloyear cooling was a significant exception to general trends of the Holocene climatic optimum.

The strongest evidence for the event comes from the North Atlantic region; the disruption in climate shows clearly in Greenland ice cores and in sedimentary and other records of the temporal and tropical North Atlantic. It is less evident in ice cores from Antarctica and in South American indices.[1] The effects of the cold snap were global, however, most notably in changes in sea level during the relevant era.

The cooling event of 6200 BCE may have been caused by a large meltwater pulse from the shrinking but still massive Laurentide ice sheet of northeastern North America — most likely when the glacial Lake Ojibway suddenly drained into the North Atlantic Ocean.[2] (The same type of action produced the Missoula floods that created the Channeled scablands of the Columbia River basin.) The meltwater pulse adversely effected the Gulf Stream and the global thermohaline circulation regulating the Earth's climate regime (an instance of warming causing cooling). Cooling occurred to 5-6°C (9-11°F) in the temperate zones, and 3°C (5°F) in the tropics: "cores drilled into an ancient coral reef in Indonesia show an abrupt sea surface cooling of about 3 degrees Centigrade."[3] Cooler and drier conditions prevailed, again as in the Younger Dryas though less extreme. Yet the changes were severe enough to impact the earliest settled human communities: the first phase of Catal Huyuk ended during the 8.2 kiloyear event. The site was abandoned and not re-occupied until about 5 centuries later, when climate conditions had improved markedly.

Drier conditions were notable in North Africa, while East Africa suffered five centuries of general drought. The initial meltwater pulse raised sea levels by as much as 1.2 meters (4 ft.), but the cooling that followed allowed a glacial advance and consequent marine regression. After 2 centuries, or by 8000 ybp (6000 BCE), global sea level had dropped by 14 meters (40 ft.). After that point, however, milder climate conditions re-asserted themselves; by 7800 ybp (5800 BCE) the global climate returned to the clement conditions that prevailed during the Holocene climatic optimum.

In 2003, the Office of Net Assessment at the U. S. Department of Defense was commissioned to produce a study on the likely and potential effects of a modern climate change. The study, conducted under ONA head Andrew Marshall, modelled its prospective climate change on the 8.2 kiloyear event, precisely because it was the middle alternative between the Younger Dryas and the Little Ice Age. The study caused a controversy when it was made public in 2004.[4]



Pre-Pottery Neolithic B
From Wikipedia, the free encyclopedia

Pre-Pottery Neolithic B (PPNB) is a division of the Neolithic developed by Dame Kathleen Kenyon during her archaeological excavations at Jericho in the southern Levant region.

The culture of this period differs from that of the earlier Pre-Pottery Neolithic A period in that people living during this period began to introduce domesticated animals to supplement their earlier agrarian diet. In addition the flint tool kit of the period is new and quite disparate from that of the earlier period. One of its major elements is the naviform core. This is the first period in which architectural styles of the southern Levant became primarily rectilinear; earlier typical dwellings were circular, elliptical and occasionally even octagonal. Pyrotechnology was highly developed in this period. One of the main features of houses were the white plaster floors, made of lime produced from limestone. The period is dated to between ca. 9600 and ca. 8000 BP.

Like the earlier PPNA people, the PPNB culture developed from the Earlier Natufian but shows evidence of a northerly origin, possibly indicating an influx from the region of north eastern Anatolia. The culture disappeared during the 8.2 kiloyear event, a term that climatologists have adopted for a sudden decrease in global temperatures that occurred approximately 8200 years before the present, or c. 6200 BCE, and which lasted for the next two to four centuries. In the following Munhatta and Yamukian post-pottery Neolithic cultures that succeeded it, rapid cultural development continues, although PPNB culture continued in the Amuq valley, where it influenced the later development of Ghassulian culture.

Work at the site of 'Ain Ghazal in Jordan has indicated a later Pre-Pottery Neolithic C period which lasted between 8200 and 7900 BP.