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Lake Agassiz, precursor of Lake Erie
Noah's Flood and the origin of Lake Erie
KNIGHT RIDDER WASHINGTON BUREAU, Tuesday, August 17, 1999
By Robert S. Boyd
"Comets may have caused Earth's great empires to fall
WASHINGTON -- Recent scientific discoveries are shedding new light on why great empires such as Egypt, Babylon and Rome fell apart, giving way to the periodic ``dark ages'' that punctuate human history.
At least five times during the last 6,000 years, major environmental calamities undermined civilizations around the world. Some researchers say these disasters appear to be linked to collisions with comets or fragments of comets such as the one that broke apart and smashed spectacularly into Jupiter five years ago.
The impacts, yielding many megatons of explosive energy, produced vast clouds of smoke and dust that circled the globe for years, dimming the sun, driving down temperatures and sowing hunger, disease and death.
The last such global crisis occurred between A.D. 530 and 540-- at the beginning of the Dark Ages in Europe -- when Earth was pummeled by a swarm of cosmic debris.
In a forthcoming book, Catastrophe, the Day the Sun Went Out, British historian David Keys describes a 2-year-long winter that began in A.D. 535. Trees from California to Ireland to Siberia stopped growing. Crops failed. Plague and famine decimated Italy, China and the Middle East.
Keys quotes the writings of a 6th-century Syrian bishop, John of Ephesus: ``The sun became dark. ... Each day it shone for about four hours and still this light was only a feeble shadow.'' A contemporary Italian historian, Flavius Cassiodorus, wrote: ``We marvel to see no shadows of our bodies at noon. We have summer without heat.'' And a contemporary Chinese chronicler reported, ``Yellow dust rained like snow.''
Researchers say similar environmental calamities occurred around 3200 B.C., 2300 B.C., 1628 B.C. and 1159 B.C. Each led to the collapse of urban societies in widely scattered portions of the globe.
Destructive as they were, the natural disasters that have plagued Earth since the dawn of human civilization are but popguns compared with the truly titanic catastrophes of prehistoric eras.
There have been at least five of these monster events, each of which wiped out most of the creatures living at the time, the fossil record shows.
The best known was a 6-mile-wide meteor that smashed into what is now the Gulf of Mexico 65 million years ago. The collision wreathed the planet in clouds of dust, poisoned the atmosphere and drove the dinosaurs, then rulers of the Earth, into extinction. Traces of the enormous crater, at least 100 miles across, created by the impact were found in 1990.
Even that wasn't the biggest blow the Earth has suffered. The mother of all extinctions, which wiped out 90 percent of living species, happened about 245 million years ago. Paleontologists say other mass extinctions occurred about 214 million, 360 million and 440 million years ago ...
These disasters, while terrible for their victims, opened the way for the survivors to flourish, diversify and -- for humans -- take over the world.
``We mammals may owe our pre-eminent position atop the Earth's food chain to a collision some 65 million years ago that wiped out most of our competition, including the dinosaurs,'' said Donald Yeomans, a NASA astronomer who tracks comets and asteroids.
These discoveries are lending weight to a revised theory of evolution. Instead of proceeding gradually by a series of tiny changes, as Charles Darwin proposed 140 years ago, life developed in a series of starts and stops, biologists now believe. They call it ``punctuated evolution,'' periods of slow development interrupted by wholesale extinctions and recoveries ...
The civilization-shattering events of the historic era ``must have been near misses, because if we had been hit by a full-blown comet in the past 10,000 years or so, we wouldn't be here today,'' said Mike Baillie, a British archaeologist who studies tree rings."
For More Information: Catastrophism
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FRESHWATER FORCING OF ABRUPT CLIMATE CHANGE DURING THE LAST GLACIATION
By Clark, P.U., et al.
Science 293(July 13, 2002):283-287. Available at http://www.sciencemag.org/cgi/content/full/293/5528/283 See article for all references noted below.
Peter U. Clark,1* Shawn J. Marshall,2 Garry K. C. Clarke,3 Steven W. Hostetler,4 Joseph M. Licciardi,1 James T. Teller5
Large millennial-scale fluctuations of the southern margin of the North American drainage to the Hudson or St. Lawrence Rivers:
We found that periods of increased freshwater flow to the North Atlantic occurred at the same time as reductions in the formation of North Atlantic Deep Water, thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume ...
* To whom correspondence should be addressed. E-mail: clarkp@ucs.orst.edu
Present address: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
A leading hypothesis about the origin of the large and abrupt fluctuations in high-latitude climate on millennial time scales invokes changes in the rate of formation of North Atlantic Deep Water and their attendant effect on oceanic heat transport (1, 2).
Numerous modeling studies demonstrate that the Atlantic thermohaline circulation is sensitive to the freshwater budget at the sites of deepwater formation (3-5): Increased freshwater flux to the North Atlantic decreases the formation of deep water, thereby reducing meridional heat transport, which causes cooling of the high latitudes.
... The best-documented case of such freshwater forcing occurred during the Younger Dryas cold interval, when continental runoff that was rerouted from the Mississippi River to the St. Lawrence River at 11,000 (Carbon-14) years Before the Present (yr B.P.) reduced North Atlantic Deep Water formation (6-9).
This mechanism for large-scale cooling has been regarded as unique to the Younger Dryas, however, and alternative mechanisms have been proposed to explain other millennial-scale climate fluctuations (10).
Our new reconstructions of North American runoff (11, 12) suggest that the freshwater rerouting that caused the Younger Dryas was, in fact, one of a number of similar events that occurred when the southern margin of the Laurentide Ice Sheet was located in the Great Lakes region (Fig. 1).
Here, we compare our time series of North American runoff during the last deglaciation to high-resolution records of North Atlantic climate and conclude that these other rerouting events caused abrupt climate change in the North Atlantic region similar to that of the Younger Dryas ...
Our reconstruction of rerouting events suggests that these initial deglacial warming trends were subsequently reversed by three sequential periods of increased freshwater flow to the North Atlantic ...
The relations between changes in the fluxes of fresh water, Thermohaline Circulation, and climate indicate that the prolonged freshwater forcing during the Oldest Dryas delayed the transition from a glacial to an interglacial climate in the North Atlantic region by suppressing formation of North Atlantic Deep Water.
Moreover, although our estimates suggest that the total flux of fresh water from North America to the Atlantic basin remained substantially higher than the modern flux throughout the deglaciation (11), our results support modeling studies (5, 7-9) in showing that the most important factor in causing changes in the Atlantic Thermohaline Circulation is the location of freshwater injection:
Increased freshwater flow through eastern outlets suppresses Thermohaline Circulation, whereas the diversion of fresh water to the Mississippi favors more vigorous Thermohaline Circulation. Further support for this hypothesis is drawn from the relations between subsequent rerouting events and abrupt climate change that we describe next ...
The onset of the Younger Dryas cold interval at 11.0 (Carbon-14) kyr (1000 years) B.P. coincided with the diversion of drainage from the Mississippi River to the St. Lawrence River as the ice margin retreated out of the Lake Superior basin (6).
Abrupt drainage of Lake Agassiz waters (9.5 × 1012 m3 of water) during the initial stages of this diversion (16) may have sensitized the North Atlantic to the increased flux through the St. Lawrence River associated with the rerouting of continental drainage (R3), which nearly doubled the amount of fresh water flowing through the St. Lawrence River (Fig. 2) (17) ...
[See below for a map of Lake Agassiz.]
The readvance of the ice margin across the eastern outlet of Lake Agassiz at about 10.0 (Carbon-14) 1000-years (kyr) caused an abrupt decrease in the freshwater flux through the St. Lawrence River by rerouting drainage to other outlets, marking the end of the Younger Dryas (22) ...
The next substantial increase in the flux of North American fresh water to the North Atlantic (R2) again occurred through the St. Lawrence River, starting about 9.1 (Carbon-14) 1000-years (kyr) B.P. and continuing until about 7.7 (Carbon-14) 1000-years (kyr) B.P.
Like the preceding Younger Dryas age rerouting event through the St. Lawrence River, this event began with the abrupt release of a large volume of water (2.5 to 7 × 1012 m3) stored in proglacial Lake Agassiz (16), followed by a lesser, but sustained, increase in flux of fresh water that was still substantially higher than that preceding the event.
Unlike the Younger Dryas, however, the primary climatic response to this rerouting event appears to be to the initial draining of Lake Agassiz, as indicated by proxy records from the North Atlantic region that identify a reduction in the formation of North Atlantic Deep Water (Fig. 2C) and a cooling at this time (19, 23) ...
Lack of a sustained climatic response to the sustained freshwater forcing during this period (as compared to the Younger Dryas) may reflect a more vigorous interglacial Thermohaline Circulation ...
The final substantive rerouting event of the last deglaciation (R1) occurred when the center of the Laurentide Ice Sheet over Hudson Bay collapsed at about 7.7 (Carbon-14) 1000-years (kyr) B.P., allowing the remaining large proglacial lakes to release on the order of 2 × 1014 m3 of lake water in less than 100 years through the Hudson Strait (27).
We find that the collapse of the Laurentide Ice Sheet also led to the capture of a large portion of the interior continental drainage (3.4 × 106 km2) by the Hudson Strait (11), resulting in a large increase in freshwater flux through this outlet that was sustained until the final melting of the ice sheet at about 7.0 (Carbon-14) 1000-years (kyr) B.P. Collapse of the ice sheet center thus resulted in a two-stage sequence of freshwater forcing similar to that of the two preceding rerouting events.
The final sequence of rerouting related to collapse of the Laurentide Ice Sheet is associated with an approximately 400-year-long cold event centered on 8.2 calendar kyr B.P. that is well expressed in a number of marine and terrestrial records in the circum-North Atlantic region (28), although the event has yet to be associated with any deep ocean response (Fig. 2). The absence of a response in [Delta ](Carbon-14) may indicate that North Atlantic intermediate or deepwater formation had increased at a site away from the point of discharge.
Based on the routing history associated with the Laurentide Ice Sheet during the last deglaciation, we conclude that changes in routing occurred most frequently along the southern ice margin when it was located in the Great Lakes region of central North America (11) ...
Millennial-scale ice margin fluctuations in the Great Lakes region occurred during longer, orbital-scale (104 to 105 years), ice margin fluctuations in this region, thus implying two distinct controls of the position of the southern ice margin that operated on different time scales.
On the orbital time scale, the ice margin responded to climate changes associated with global boundary conditions, such as insolation, atmospheric greenhouse gas concentrations, and ocean circulation. Internal ice sheet dynamics may have been particularly important during deglaciations.
Explaining the millennial-scale fluctuations of the ice margin has been more problematic, but the relation we document here suggests that these fluctuations in the Great Lakes region may have been part of an oscillatory behavior that controlled rerouting events and abrupt changes in North Atlantic sea surface temperatures (Fig. 3).
... Increased flux of fresh water through this outlet suppressed North Atlantic Deep Water formation that caused cooling of the North Atlantic. Colder conditions allowed the ice margin to readvance and eventually block the eastern outlet, which decreased the outflow of fresh water to the North Atlantic. Subsequently, the rate of North Atlantic Deep Water formation increased and reestablished warming ...
Regional climate modeling results (31) identify an additional oscillatory behavior involving lake-atmosphere-ice sheet interactions that would have occurred when the ice margin was located near the critical eastern outlet at ~49°N (Fig. 1). This lake-effect oscillation may also have induced fluctuations of the ice margin, leading to the diversion of fresh water between the Mississippi and St. Lawrence Rivers.
Our proposed feedback models share important characteristics with the salt-oscillator hypothesis (10), which postulates that warm North Atlantic Sea Surface Temperatures increased the melting rate of (and thus the freshwater flux from) adjacent ice sheet margins, and vice versa.
We suggest instead, however, that large changes in freshwater flux to the North Atlantic that induced changes in Thermohaline Circulation were caused by rerouting of continental runoff associated with a fluctuating ice margin ...
Model sensitivity tests suggest that warmer North Atlantic Sea Surface Temperatures may have induced decreases in net moisture (precipitation minus evaporation), whereas colder North Atlantic Sea Surface Temperatures may have induced increases in net moisture, on the order of 0.1 Sv (1 Sv = 106 m3 s[-]1) over the North
Atlantic Ocean (29); an additional freshwater forcing of magnitude comparable to that of our reconstructed rerouting events. The increased flux of icebergs (24) from marine ice sheet margins that occurred in response to cold events in the North Atlantic would have further amplified these feedbacks ...
The system could have operated essentially as a free-running oscillator for as long as the ice margin remained in this region, inducing high-amplitude climate variations such as those that occurred during the last deglaciation ...
Volume 293, Number 5528, Issue of 13 Jul 2001, pp. 283-287.
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Quaternary International, Vol. 68-71 (1) (2000) pp. 297-308
CALCAREOUS DUNES OF THE UNITED ARAB EMIRATES AND NOAH'S FLOOD: THE POSTGLACIAL REFLOODING OF THE PERSIAN (ARABIAN) GULF.
J.T. Teller, K.W. Glennie, N. Lancaster and A.K. Singhvi
ABSTRACT
Aeolian dunes cover most of the United Arab Emirates and a large part of the eastern Arabian Peninsula. Although these sands, as well as older aeolianites, are largely composed of quartz, there is a high percentage of detrital carbonate in them south of the Persian (Arabian) Gulf for more than 40 km; this percentage decreases inland.
These carbonate grains consist mainly of marine bioclastic fragments and calcareous ooids, and were derived from the floor of the Persian Gulf, which was exposed during low sea level of the last glacial period.
The postglacial rise in sea level rapidly reflooded the floor of the Persian Gulf, cutting off the source for these aeolian sediments. Between 12 and 6 ka, the sea transgressed more than 1000 km, inundating the extended route of the Tigris-Euphrates River and forcing people living on the exposed floor of the Gulf to abandon their settlements.
Because of the varying rate of eustatic sea level rise, these waters at times flooded across the flat floor of the Persian Gulf at more than a kilometer per year.
We proposed that the stories of a great flood, recorded in the Bible as Noah's Flood and in Babylonian history on clay tablets (excavated in the Tigris-Euphrates delta) as the Epic of Gilgamesh, are a record of this rapid postglacial flooding of the floor of the Persian Gulf.
[See above for a discussion of the causes of the reflooding. See the following for some background information on Lake Erie:]
... The Niagara table land mass extends 100 kilometers (62 miles), both east and west from the Niagara River.
This plain is a small part of the Great Lakes low lands in which Lake Superior, Lake Michigan, Lake Huron, Lake Erie and Lake Ontario lie.
The areas north and south of the Great Lakes low lands are the high lands ...
The last glacial ice age occurred during three distinct periods of time during the past 65,000 years. The glacier originated east of Hudson Bay in northern Quebec and Labrador. This great glacier was known as "the Wisconsin Glacier".
The early Wisconsin Glacier covered the Niagara District and most of the northern North America 65,000 years ago. This glacier remained for a period of approximately 15,000 years before retreating 50,000 years ago.
The middle Wisconsin Glacier advanced again over the Niagara District 40,000 years ago. It remained for approximately 8,000 years before retreating 32,000 years ago.
The late Wisconsin Glacier advanced again 20,000 years ago. It remained for approximately 8,000 years before beginning it's final retreat 12,000 years ago ... The Niagara Escarpment was covered with a sheet of ice 2 - 3 kilometers thick (Wisconsin Glacier) 23,000 - 12,000 years ago.
As the Glacier retreated, the water levels slowly lowered forming four lakes:
Glacial Lake Algonquin - (area including Lake Superior, Lake Michigan and Lake Huron)
Glacial Lake Warren - small (Lake Erie)
Glacial Lake Iroquois - small (Lake Ontario)
Glacial Lake Tonawanda - area western New York
Glaciers ranged up to 4.8 kilometers (3 miles) thick. Ice at 1.2 kilometers (1 mile) thick would exert a pressure of 150 tons per square foot. It is estimated that the weight of the glacier depressed the earth 61 meters (200 feet). When the glacier retreated the land began to rise in what is referred to as glacial rebound.
... Scientists have suggested that the eastern part of the North American continent is still in the process of tilting as part of the glacial reflex action. As the crust of the earth rises along the eastern seaboard the water flowing from the Great Lakes system will become slower ...
As the late Wisconsin Glacier retreated northward, it created several outlets:
An outlet from Lake Algonquin (Lake Huron) to Lake Iroquois (Lake Ontario)
An outlet from Lake Algonquin (Lake Huron) through Lake Nippissing to the Ottawa Valley
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An outlet from Lake Iroquois (Lake Ontario) through the Mohawk Valley (Rochester) to the Hudson River
The rising of the lands from glacier rebound finally cut off these outlets with the exception of the Niagara River.
During the period of glaciation and shortly afterwards, the climate in Niagara was arctic. Vegetation was tundra and arctic fauna.
Glacial Lake Agassiz had a great influence on the Lake Erie basin. Eleven thousand (11,000) years ago, Lake Aggassiz initially drained southward over a divide into the Mississippi River basin. As the divide rose from isostatic rebound, the entire flow of the Upper Great Lakes flowed into the Lake Erie basin...
... 11,000 years agm and again 4,000 - 5,000 years ago ... the water level in the Erie Basin was much higher from the influx of waters from glacial Lake Agassiz ...
Twelve thousand years ago, the waters of the much larger Lake Erie began to flow into a larger Lake Ontario. The Niagara River began to flow from the Lake Erie basin down the present path of the river ...
See the original article.
HISTORICAL SKETCH OF AVON, OHIO, TO 1974
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