New evidence suggests an impact between Earth and a speeding asteroid may have resulted in a massive global fire and major extinction almost 13,000 years ago. The Cosmic Companion talks with lead researcher Christopher Moore.
Less than 13,000 years ago, the world suffered a massive cold snap that wiped out vast numbers of species. Known as the Younger Dryas (YD), this period saw the loss of infamous animals such as woolly mammoths, saber-tooth cats, giant sloths and mastodons.
As species died off, human populations in regions around the world also saw their populations sink precipitously. The Clovis people, a prehistoric Paleoamerican culture (for example), saw a significant drop in their population at this time.
Massive wildfires following an impact may have blocked sunlight over vast regions of the globe, causing temperatures to drop, wiping out large numbers of plant and animal species. At the peak of the fires, as much as 10 percent of the Earth’s land surface, or about 10 million square kilometers, was on fire.
Since 2007, investigators have speculated that an impact from space may have altered the Earth’s climate, leading to this mass extinction. This idea became known as the Younger Dryas Impact Hypothesis.
Sticks and Stones…
Archaeologist Christopher Moore of the University of South Carolina led a team of investigators to White Pond in South Carolina, where they collected sediment from the lake, allowing researchers to view geological evidence of conditions there at the start of the Younger Dryas extinction. the cores revealed a 10 cm (four inch) wide band, dating from the century between 12,835 and 12,735 years ago.
At the site, the team found traces of platinum (potentially debris from an asteroid) along with high concentrations of soot, suggesting a massive wildfire in the region at the star of the Younger Dryas.
Concentrations of a type of fungal spore, a marker for dung droppings of larger herbivores, was rare during this time, evidence for a significant loss of ice-age megafauna beginning roughly 12,800 years before our time.
Traces of platinum dated to that era have been found in locations around the world, including North America, western Asia, Europe, South Africa, and Chile. This metal is fairly rare on Earth, but is relatively common in asteroids.
Traditionally, the Younger Dryas Impact Hypothesis was thought to have affected the northern hemisphere, leaving the southern half of the globe relatively untouched. However, recent findings showing deposits of platinum in Chile and South Africa show the impact affected regions of the globe south of the equator as well.
In the recently-discovered Hiawatha Crater in Greenland, researchers searched ice cores, finding high concentrations of platinum and iridium (another material which is rare on Earth but not in asteroids). This finding could be “smoking gun” evidence that the crater was the leftover remains of the impact which brought about this global extinction.
Evidence also suggests that, instead of a single impact, this event may have featured a series of airbursts and collisions around the globe.
The Earth, which had been warming since the end of the previous ice age which ended 4,500 years before, was plunged again into darkness and cooler temperatures. This return to the ice age lasted nearly 1,400 years before temperatures suddenly snapped back to warmer conditions.
“The end of the Younger Dryas, about 11,500 years ago, was particularly abrupt. In Greenland, temperatures rose 10°C (18°F) in a decade,” the National Centers for Environmental Information reports.
If an impact like this one took place in our modern age, temperatures in the northern hemisphere could drop as much as eight degrees Celsius (14 degrees Fahrenheit) — the difference between Miami, Florida into Montreal, Canada. This would have devastating consequences for our modern society, Moore predicts.
“A similar impact today could cause major disruptions to modern civilization. Depending on where it hits, it could cause wildfires and a short-term (few weeks to months) impact winter as well as oceanographic changes and climate change like what we had during the Younger Dryas. These could prove challenging to a modern industrial civilization,” Moore describes for The Cosmic Companion.
Winter is Coming
There are still many questions left unanswered about a potential YD impact, and significant data remains undiscovered.
Researchers are uncertain about the composition of the impactor, or how large the object which impacted the Earth was when it entered our atmosphere.
“If the recently found Hiawatha Crater can be dated to the Younger Dryas, we will have much better information about the size and mass of that impactor, although there are likely others as well as those that exploded in the atmosphere,” Moore explains for our readers.
Soon after the discovery of the Hiawatha impact crater under the ice of northwest Greenland, another similar feature was found just 114 miles away.
The underlying causes of the decline of the Clovis people and the extinction of ancient species almost 130 centuries ago remains unanswered, Moore and his team believe their evidence in favor of the Younger Dryas Impact Hypothesis will eventually be accepted among most researchers and the general public.
Still, some researchers hold to the idea that as ice dams in freshwater lakes in North America melted, they released fresh water into the North Atlantic, shutting down ocean circulation and cooling the environment.
“Those are big debates that have been going on for a long time. These kinds of things in science sometimes take a really long time to gain widespread acceptance. That was true for the dinosaur extinction when the idea was proposed that an impact had killed them. It was the same thing with plate tectonics. But now those ideas are completely established science,” Moore explained in a press release from the U of SC.
“The dinosaurs became extinct because they didn’t have a space program.”
— Larry Niven
Like the impact which finally ended the age of the dinosaurs, an asteroid which resulted in the YD extinction would have left its mark around the globe in the form of rare metals. However, calculations suggest this more recent extinction would have been caused by a much smaller body than the one that spelled final doom for dinosaurs and many other forms of life over 65 million years ago.
“The YD impact is orders of magnitude smaller, but still significant, with energy likely distributed over the globe in the form of impacts and airbursts from a fragmented comet or asteroid,” Moore describes.
The Younger Dryas is named in honor of Dryas octopetala, a wildflower which can tolerate cold temperatures, and which flourished throughout Europe during the cold snap.
This new study was published in the journal Scientific Reports, a publication of Nature.
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