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73c2a8d
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Around 12,800 years ago, it was as though an enchantment of ice had gripped the earth. In many areas that had been approaching terminal meltdown full glacial conditions were restored with breathtaking rapidity and all the gains that had been made since the LGM were simply stripped away: 'Temperatures ... fell back on the order of 8-15 degrees centigrade ... with half this brutal decline possibly occurring within decades. The Polar Front in the North Atlantic redescended to the level of Cabo Finisterre in northwest Spain and glaciers readvanced in the high mountain chains. With respect to temperature the setback to full glacial conditions was nearly complete ...' For human populations at the time, in many except the most accidentally favoured parts of the world, the sudden and inexplicable plunge into severe cold and aridity must have been devastating. And in the Karakoram-Himalayan region, as in other glaciated areas, it is very likely that it was accompanied by a significant readvance of the ice-cap that previously had been in recession for some 7000 years.
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younger-dryas
ice-sheets
ice-age
deep-human-history
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Graham Hancock |
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ae33dc1
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Areas that are densely populated today, Chicago, New York, Manchester, Amsterdam, Hamburg, Berlin, Moscow -- in fact most of North America and northern Europe -- were absolutely due to the fact that they were covered by ice-caps several kilometers thick. Conversely, many areas that are uninhabitable today -- on account of being on the bottom of the sea, or in the middle of hostile deserts such as the Sahara (which bloomed for about 4000 years at the end of the last Ice Age) -- were once (and relatively recently) desirable places to live that were capable of supporting dense populations. Geologists calculate that nearly 5 per cent of the earth's surface -- an area of around 25 million square kilometers or 10 million square miles -- has been swallowed by rising sea-levels since the end of the Ice Age. That is roughly the equivalent to the combined areas of the United States and the whole of South America. It is an area almost three times as large as Canada and much larger than China and Europe combined. What adds greatly to the significance of these lost lands of the last Ice Age is not only their enormous area but also -- because they were coastal and in predominantly warm latitudes -- that they would have been among the very best lands available to humanity anywhere in the world at that time. Moreover, although they represent 5 per cent of the earth's surface today, it is worth reminding ourselves that humanity during the Ice Age was denied useful access to much of northern Europe and North America because of the ice-sheets. So the 25 million square kilometers that were lost to the rising seas add up to a great deal more than 5 per cent of the earth's useful and habitable landspace at that time.
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uninhabitable
meltwater-pulses
ice-sheets
ice-age
geology
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Graham Hancock |
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1c35051
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In 1988 the German oceanographer Hartmut Heinrich was the first to come up with the firm geological evidence for such a cataclysmic 'iceberg-calving' process during the last Ice Age. By examining deep-sea drill cores sampled at various points across the North Atlantic he demonstrated the existence of widely dispersed layers of 'ice-rafted detritus' -- millions of tonnes of rocks and rocky debris that had once stood on land, that had been clawed up by the ice-sheets and that had ultimately been carried out to sea frozen into huge icebergs: 'As they melted they released rock debris that was dropped into the fine-grained sediments of the ocean floor. Much of this ice-rafted debris consists of limestones similar to those exposed over large areas of eastern Canada today. The Heinrich layers as they have become known, extend 3000 kilometers across the North Atlantic, almost reaching Ireland.' The Heinrich layers record at least six separate discharges of 'stupendous flotillas of ice-bergs' into the North Atlantic -- discharges that are now known, obviously enough, as 'Heinrich Events' and that are thought to have unfolded in concentrated bursts of activity that may, in each case, have lasted less than a century. Because of the progressive thickening of the Heinrich layers towards the western side of the Atlantic and the continuation of this trend into the Labrador Sea in the direction of Hudson Bay, it is obvious to geologists that 'much of the floating ice was sourced from the Laurentide ice-sheet'. However, other debris has been found intermingled in some Heinrich layers that 'could only have come from separate ice-sheets covering not only Canada, but Greenland, Iceland, the British Isles and Scandinavia'. Likewise, research into southern hemisphere ice-caps in the Andes and New Zealand shows that these too 'grew and then collapsed synchronously with the ice-rafting pulses recorded in the North Atlantic'. The implication [...] is that some 'global rather than regional forcing of climate change' must have been at work.
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icebergs
ice-sheets
ice-age
deluges
geology
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Graham Hancock |
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b75e4ff
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Thomas Crowley and Gerald North, oceanographers at Texas A&M University, describe the melting of the great ice-sheets at the end of the last Ice Age as 'one of the most rapid and extreme examples of climate change recorded in the geologic record'.
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younger-dryas
ice-sheets
ice-age
geology
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Graham Hancock |
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6b3bf58
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We know that relatively minor sea-level rises could set off major ice-sheet breakups, and it has been suggested by Stephen Oppenheimer that the tremendous earthquakes caused by isostatic rebalancing at the end of the Ice Age could have stirred up 'mountain-topping superwaves' in the northern regions of the Atlantic and Pacific Oceans. Other than Oppenheimer's own investigations, however, my impression is that while many brilliant individual scientists have studied individual post-glacial phenomena in great depth, very little has yet been done to investigate all these phenomena together as part of a complex system or to consider the effects on the earth and its human population of multiple, interacting cataclysms -- floods, lands subsiding into the sea, earthquakes, volcanic eruptions -- all occurring at the same time.
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earthquakes
ice-sheets
superwaves
volcanism
deep-human-history
sea-level-rises
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Graham Hancock |
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d35039c
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As the discoverer and principal excavator of Murray Springs, [...] Haynes deserves credit for drawing attention to a very curious aspect of the site--a distinct dark layer of soil draped 'like a shrink-wrap,' as Allen West puts it, over the top of the Clovis remains and of the extinct megafauna--including Eloise. Haynes has identified this 'black mat' (his term) not only at Murray Springs but at dozens of other sites across North America, and was the first to acknowledge its clear and obvious association with the Late Pleistocene Extinction Event. he speaks of the 'remarkable circumstances' surrounding the event, the abrupt die-off on a continental scale of all large mammals 'immediately before deposition of the ... black mat,' and the total absence thereafter of 'mammoth, mastodon, horse, camel, dire wold, American lion, tapir and other [megafauna], as well as Clovis people.' Haynes notes also that 'The basal black mat contact marks a major climate change from the warm dry climate of the terminal Allerod to the glacially cold Younger Dryas.' From roughly 18,000 years ago, and for several thousand years thereafter, global temperatures had been slowly but steadily rising and the ice sheets melting. Our ancestors would have had reason to hope that earth's long winter was at last coming to an end and that a new era of congenial climate beckoned. This process of warming became particularly pronounced after about 14,500 years ago. Then suddenly, around 12,800 years ago, the direction of climate change reversed and the world turned dramatically, instantly cold--as cold as it had been at the peak of the Ice Age many thousands of years earlier. This deep freeze--the mysterious epoch now known as the Younger Dryas--lasted for approximately 1,200 years until 11,600 years ago, at which point the climate flipped again, global temperatures shot up rapidly, the remnant ice sheets melted and collapsed into the oceans, and the world became as warm as it is today.
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pleistocene
paleontology
younger-dryas
ice-sheets
extinction
climate-change
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Graham Hancock |