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ScienceDaily (Jan. 20, 2009) — First came the earthquakes, then the torrential rains. But the relentless march of sand across once fertile fields and bays, a process set in motion by the quakes and flooding, is probably what did in America's earliest civilization.
So concludes a group of anthropologists in a new assessment of the demise of the coastal Peruvian people who built the earliest, largest structures in North or South America before disappearing in the space of a few generations more than 3,600 years ago.
"This maritime farming community had been successful for over 2,000 years, they had no incentive to change, and then all of a sudden, 'boom,'" said Mike Moseley, a distinguished professor of anthropology at the University of Florida. "They just got the props knocked out from under them."
The extinction of the woolly mammoth some 3,600 years ago was driven by the disappearance of its icy habitat combined with the emergence of human hunters, scientists have confirmed. The relative importance of climate and hunting for the mammoth's fate has long been debated but rarely assessed quantitatively.
WASHINGTON (AP) -- The rains stopped coming, the temperature rose and the great grasslands of North Africa turned to desert a few thousand years ago -- changes that may have helped spur development of civilization in the Nile Valley.
The change to today's arid climate was not gradual, but occurred in two episodes -- the first 6,700 to 5,500 years ago and the second 4,000 to 3,600 years ago, according to a paper published Thursday by the journal Geophysical Research Letters.
"The latter was very severe, ruining ancient civilizations and socio-economic systems," the researchers wrote.
A team of researchers headed by Martin Claussen of Germany's Potsdam Institute for Climate Impact Research analyzed computer models of climate over the past several thousand years.
They concluded that the change to today's desert climate in the Sahara was triggered by changes in the Earth's orbit and the tilt of Earth's axis.
Scientists have learned the second largest volcanic eruption in human history -- the Bronze Age eruption -- was much larger than thought.
Researchers from the University of Rhode Island and the Hellenic Center for Marine Research in Athens, Greece (using techniques similar to those employed by oil companies to search for offshore deposits), earlier this year found deposits of volcanic pumice and ash up to 260 feet thick extending more than 15 miles in all directions from the Greek island of Santorini.
These deposits have changed our thinking about the total volume of erupted material from the Minoan eruption, said URI volcanologist Haraldur Sigurdsson.
Irish Tree Rings and an Event in 1628 BC
In prehistoric times, oaks growing on the surface of Irish raised bogs were recording rare extreme events.
These extreme events are characterized by the simultaneous occurrence of the narrowest rings in the lifetime of trees throughout a wide geographical spread of sites.
Significantly the dates of these extreme 'narrowest ring' events coincide with the estimated dates for major volcanic eruptions as recorded in the Greenland ice-cap. One of these events occurs in the decade of the 1620s BC and coincides very precisely with a previously suggested volcanic event at 1626 BC (now 1627 BC) put forward by LaMarche.
One is led to the inevitable conclusion that some major hemispheric event took place in the decade of the 1620s BC, and a strong circumstantial case can be constructed that the event was volcanic in origin. Since the dating is based on precisely dated tree rings no further refinement of the date of the event - probably 1628 BC - is required.
Michel R. Legrand and Robert J. Delmas of Laboratoire de Glaciologie et Geophysique de l'Environment published an article "Soluble Impurities in Four Antarctic Ice Cores Over the Last 30,000 Years" in Annals of Glaciology (10, 1988, pp 116-120). They graphed the Oxygen 18 variations and the ionic components Na = NH (sub4) and Ca (sup 2) and H and Cl and NO (sub 3) and SO (sub 4). The time scale for each ionic component level as well as the O (sup 18) levels stretches back 30,000 years. The graph shows correlations to spikes at 5,200 BC, 8,800 BC, 12,400 BC, c. 16,000 BC, c. 19,600 BC. All of these were times of great geologic stress.
When looking at the data and taking into account the acknowledged dating inaccuracies (some of the ranges of dates can go 100 years in either direction of the spike, even though the spiking is regular and rhythmic) for the more recent dates, and 3 to 600 years variance for the older dates - especially when one considers that these are broad analyses and nobody was really looking for anything specific - they just said "wow! look at that wavy line!" we find that the southern ice cores do not register the same as the northern ones. The 1628 BC event that really slammed the tree rings shows almost no registration in the antarctic cores in terms of volcanic activity. But the northern cores show the activity beginning 1644 BC.
The evidence for the 5200 BC event is strong in the Dome C core. The 8,800 BC event is well marked - in fact, seems to be the strongest of them all... The Flood of Noah, no doubt! The oxygen 18 isotope variation is noticeable, the rise in sea-salt, eleveated levels of C 1 and C1/Na. There is an extreme spike in SO (sub 4) and H readings suggesting widespread volcanic activity - great earth changes were happening at that time, and they registered in the climate, the oceans, and were preserved in ice.
The 12400 BC event is extremely pronounced in the cores. The graphs show a quick, vast change including the end of the Wisconsin Ice Age (ee: Evidence of Nuclear Activity in Paleoindian Times).
Originally posted by davesidious
reply to post by Amaterasu
There's no evidence for that pseudo-scientific hogwash.
reply to post by DEEZNUTZ
We passed the centre of the galaxy in 1998, I believe, so galactic alignment is a bit passe. Also, galactic alignments happen every 36 years, so if it was such a big thing, there'd be no Earth left.
Also, the Earth's magnetic field can shift and flip all it wants, with no ill-effect on us, as the field will be there through the flip, it just won't be as pretty as it currently is.
So this is just more baseless 2012 conjecture. Yay.
Originally posted by davesidious
We passed the centre of the galaxy in 1998, I believe, so galactic alignment is a bit passe. Also, galactic alignments happen every 36 years, so if it was such a big thing, there'd be no Earth left.
Also, the Earth's magnetic field can shift and flip all it wants, with no ill-effect on us, as the field will be there through the flip, it just won't be as pretty as it currently is.
So this is just more baseless 2012 conjecture. Yay.
To predict the length of time between the Solar System's crossings of the galactic plane, astronomers have had to gauge the up-and-down motion statistically, using the numbers and the velocities of many sample stars distributed above and below the plane. The mathematical analysis then yields as a final result both the period of the up-and-down motion and the space density of matter in the flat galactic disk. In the same way that a pendulum swings much faster on Earth than in a low-gravity environment, such as an Earth-orbiting spacecraft, the surprisingly large space density found in the galactic disk gives the Solar System an unexpectedly short up-and-down period of 30 to 35 million years. This new measurement agrees uncannily well with the known impact cratering period on Earth. And it is likely that another big impact on Earth will happen sometime soon, at least within the next million years, because the inner Solar System seems to be in a comet shower now.