Tag Archives: Younger Dryas

The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here Photographed by: Mukul Sharma

Meteor impact in Canada may have triggered the Big Freeze that caused mass extinction and forced humans into agriculture

The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here Photographed by: Mukul Sharma

The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here
Photographed by: Mukul Sharma

A recent study has revived an older controversy, after  Dartmouth Professor Mukul Sharma and his team reported what they claim is the first conclusive evidence that links an extraterrestrial impact in Canada with the beginning of the Younger Dryas, a period of abrupt climate change that caused major cooling through the Earth. During this time, a number of species became extinct and the human hunger-gatherer population transitioned to an agricultural based lifestyle.

In the 1.5-billion-year-old Quebecia terrane in northeastern Canada, near the Gulf of Saint Lawrence and modern day Quebec, researchers believe a comet or meteor impact took place, after at they analyzed the chemical composition of spherules discovered at the location (droplets of solidified molten rock expelled by the impact of a comet or meteor). The chemical composition matched those of spherules  deposited in Pennsylvania and New Jersey at the start of the Younger Dryas period.

The Younger Dryas or the Big Freeze as its also been called began some 12,900 years ago and enveloped the world in a short lasting (in geological terms – some 1,000 years) glacial period. During this time, a number of species became extinct, including saber-toothed cats, giant sloths, and mastodons. The same event marked the end of the Clovis hunter-gatherer culture in favor of the adoption of farming and animal husbandry, as supported by evidence dated from the time collected from the Near East – coincidentally or not the region was also home to the earliest city settlements we know of (Ur, Uruk).

“The Younger Dryas cooling impacted human history in a profound manner,” says Dartmouth Professor Mukul Sharma, a co-author of the study. “Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture.”

The newly discovered spherules do not originate from the 4km-wide Corossal crater – a known impact crater in Quebec. This fact leads the researchers to conclude that a series of comet or meteor impacts caused the beginning of the Younger Dryas 12,900 years ago. The meteor/compact impact theory sparking the Younger Dryas isn’t new and has for a long time been contested. The current accept theory is that an ice dam rupture released huge amounts of freshwater into the Atlantic. This in turn was thought to have shut down ocean currents moving warm tropical water, resulting in colder conditions.

“It may well have taken multiple concurrent impacts to bring about the extensive environmental changes of the Younger Dryas,” says Sharma. “However, to date no impact craters have been found and our research will help track one of them down.”

Worth noting is that ZME Science reported earlier of a newly discovered meteor impact site in Mexico dating from 13,000 years ago, where an eclectic geological mix of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.  Apart from the Mexican site, the researchers also identified sediment layers of the same age, dating back 13,000 years ago,  in Canada, the United States, Russia, Syria and various sites in Europe.

Findings appeared in the journal PNAS.

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

Trigger for Earth’s last ‘big freeze’ located by geoscientists

Some 12,900 years ago, a massive flood of melted freshwater in the Arctic caused a 1,200-year-long chill nicknamed the “Big Freeze.” During this time much of the Northern Hemisphere was engulfed by centuries of cold, which caused the extinction of most great mammals, like mammoths, as well as the Clovis people. For decades, scientists have been debating from where and how did the freshwater flood flow. Now, a team of scientists may have finally reached a conclusion after they devised a computer model.

Technically known as the Younger Dryas, this specific period wasn’t a glacial period or what’s commonly referred to as an “ice age”, since it was a cold time in an otherwise warm span between ice ages. In other words, the Big Freeze wasn’t part of the Earth’s natural warm/cold cycle, it was triggered by an event. Previous theories held that a cosmic impact caused the Big Freeze, however recently scientist have reached to a common conclusion that a vast pulse of freshwater is to blame.

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

A new model of flood waters from melting of the Laurentide Ice Sheet and large glacial lakes along its edge that covered much of North America from the Arctic south to New England over 13,000 years ago, shows the meltwater flowed northwest into the Arctic first. This weakened deep ocean circulation and led to Earth’s last major cold period.The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue). (c) Alan Condron, UMass Amhers

The source of this great flood was the massive glacial Lake Agassiz, located along the southern margin of the Laurentide Ice Sheet, which at its maximum 21,000 years ago was 6,500 to 9,800 feet (2,000 to 3,000 meters) thick and covered much of North America, from the Arctic Ocean south to Seattle and New York. Researchers believe the flood was caused by a sudden melting of an ice dam. The subsequent massive influx of freshwater diluted the circulation of saltwater in the North Atlantic, disrupting the ocean “conveyer belt” that transports heat to Europe and North America. The weakening of this circulation caused by the flood resulted in the dramatic cooling of North America and Europe.

Until recently, however, scientists weren’t sure whether the meltwater flowed northwest into the Arctic first, or east via the Gulf of St. Lawrence.

“This episode was the last time the Earth underwent a major cooling, so understanding exactly what caused it is very important for understanding how our modern-day climate might change in the future,” says Condron of UMass Amherst’s Climate System Research Center

Working with Peter Winsor at the University of Alaska, Condron used a high resolution, global, ocean-ice circulation model that is 10 to 20 times more powerful than previously attainable, to compare how different drainage outlets was delivered to the sinking regions in the North Atlantic. If Lake Aggasiz drained into the North Atlantic down the St. Lawrence River then the thermohaline circulation would have weakened by less than 15 percent. In contrast, when the meltwater first drains into the Arctic Ocean, narrow coastal boundary currents can efficiently deliver it to the deep water formation regions of the sub-polar north Atlantic, weakening the thermohaline circulation by more than 30 percent.

These findings hint that shifts in the flow of water in the Arctic could dramatically alter today’s climate.

“However, in our modern-day climate, there are no sources of freshwater as large as the glacial lakes or Laurentide Ice Sheet readily available to suddenly flood into the ocean,” Condron said. “As a result, we should be cautious using this study as an analog for what might trigger modern-day abrupt climate change.”

The researchers are able, however, to put their model to good use in other instances, though far less extreme, like studying the effects of the potential melting of large ice sheet over Greenland and changes in the hydrological cycle, such as increased river runoff of the Arctic in the near-future.

Findings were published in the journal Proceedings of the National Academy of Sciences.

Source: University of Massachusetts at Amherst

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

Comet might have catastrophically collided with Earth 13,000 years ago

A recently published study suggests that the Earth might have been visited by a giant space rock 13,000 years ago, an event which might have sparked an unusual cold period in the planet’s climate history.

The Younger Dryas, also known as the Big Freeze, was a brief period of cold climatic conditions and drought which occurred some 13,000 years ago. Scientists are still debating what exactly caused this sudden shift in climate, and one highly controversial theory has it that a major cosmic impact with Earth might be to blame for the onset of this unusual cold climatic period. Suspicions of such an event have been voiced for a few years now, but up until now no clear evidence to support this hypothesis was found.

Recently, an international team of researchers  has identified a nearly 13,000-year-old layer of thin, dark sediment buried in the floor of Lake Cuitzeo in central Mexico. This layer is filled with an eclectic geological mix of materials, including nanodiamonds, impact spherules, and more, which, according to the researchers, are the result of a cosmic body impacting Earth.

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

Scanning electron microscope image showing the ‘tectonic' effects of the collision of one spherule with another during the cosmic impact. (c) UCSB

The theory was long dismissed since no impact crater could be found, but the researchers involved in the study argue that a lot of cosmic bodies simply disintegrate into the atmosphere before even getting the chance to reach the ground. They claim the hypothetical comet event might have actually exploded in mid-atmosphere.

“If you don’t have a crater, you’re a little bit lost,” said space scientist Ted Bunch of Northern Arizona University, a member of the research team. “Here what we have is something similar to an aerial bomb blast. With these aerial bursts, with time all the evidence is wiped away unless it’s buried.”

Apart from the Mexican site, the researchers also identified sediment layers of the same age, dating back 13,000 years ago,  in Canada, the United States, Russia, Syria and various sites in Europe. The same  family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite, which is unique to cosmic impact, and high velocity collided spherules were found. These features are impossible to form through geologically natural processes here on Earth, and seem to lead to the conclusion of a cosmic impact. Since evidence has been scattered through the world, including Mexico and the tropics, with this latest find, it seems a large, previously fragmented body, greater than several hundred meters in diameter entered the atmosphere at a relatively shallow angle.

“If you have an event like this in a 1- or 2-inch layer that dates to exactly the same age over a very large area, and you have high-temperature materials and nanodiamonds in there, the evidence pretty well points to an event that as pretty disastrous,” Bunch said.

A heat flash fireball in the sky might have caused an ice age

Images of single and twinned nanodiamonds show the atomic lattice framework of the nanodiamonds. Each dot represents a single atom. (c) UCSB

Images of single and twinned nanodiamonds show the atomic lattice framework of the nanodiamonds. Each dot represents a single atom. (c) UCSB

Currently, there are only two known continent-wide layers with abundance peaks in nanodiamonds, impact spherules, and aciniform soot. One is the Younger Dryas layer, and the other is 65-million-year-old Cretaceous-Paleogene boundary layer, which sets it on par with the current leading dinosaur extinction theory of a giant asteroid impact. The Younger Dryas period is associated with the extinction of a large number of mammals, including Mammoths and Saber-toothed cats.

“The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits,” said James Kennett, professor of earth science at UC Santa Barbara. “These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.’ “

A comet impacting Earth’s atmosphere at a typical velocity of 30 miles/second would have caused a deadly heat flash reaching about 3,000 to 4,000 degrees Fahrenheit (1,600 to 2,200 degrees Celsius), obliterating any sings of life across a wide radius around it – like a deadly ball of fire. The researchers aren’t claiming, however, that this celestial impact event actually started the Younger Dryas  ice age, but rather argue that it surely had a significant effect on Earth’s climate.

“We’re not going to come out and say it did do it, but it’s more than a coincidence that the timing happened exactly the time that a lot of climatic conditions occurred and you had the loss of various species,” Bunch said.

The researchers’ findings were published in the journal Proceedings of the National Academy of Sciences.

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