Why is there a huge crater under the Greenland icecap?

This article looks at the Greenland impact crater that was recently discovered by Kurt Kjaer.

Beneath Hiawatha glacier, in Greenland, lies a huge 31km wide impact crater. large enough to swallow London, what caused it and when?

On a bright clear day in July 2018 Kurt Kjaer, a geologist with the natural history museum of Denmark flew over the desolate frigid wilderness of Northwest Greenland. The helicopter sped towards the Hiawatha glacier and its outflow river. Here, tumbling rocks revealed a long lost secret.

Landing near to the rushing waters Kjaer discovered evidence of a colossal impact. Most importantly it was recent, less than 100,000 years old and maybe much younger.

13,000 years ago something extraordinary happened,a major cataclysm shook the world. Many species of mega-beasts became extinct. Huge mammoths were frozen with food still in their mouths.

Although not as devastating as the dinosaur-killing asteroid, 65 million years ago. This 1.5 km wide iron meteorite would have ruined your whole day! Impacting with a force of 700 megatonnes, the surrounding ice would have vaporized as the meteorite blasted through it, to the rocky surface.

If you were happily hunting mammoths several hundred kilometres away, the shock wave would have blown you off your feet.

Extinctions due to the Greenland impact crater

In North America the thriving Clovis culture suddenly disappeared. One minute they were there and the next they were gone. What happened?

Interlude

The hunter glanced at the sky as a rumbling concussion shook the rocky ground. Cursing, he gripped his spear tightly as the startled deer fled into the undergrowth. Black clouds darkened the horizon as the first burning debris began to fall. Trees bent in the quickening breeze and then the forests began to burn. Choking in the eye watering smoke, he staggered back to the camp. Already a black rain was falling.

All over the USA and Canada a black mat covers the land. Dated to 13,000 years ago. Did this mark the end of the hunter Gatherers?

The Clovis culture was widespread and successful. They were closely associated with native Americans. Beautiful stone arrow heads were found at a site in Clovis new Mexico where there were signs of the beast they hunted. The population declined during the Younger Dryas. Some academics suggest that over hunting was the cause, however it is more likely due to the deep freeze and lack of hunting opportunities.

Burning and the Younger Dryas.

How did mass burning cause a giant freeze? For more than a thousand years a period known as the Younger Dryas brought a new deep freeze to the world. This started 12,800 years ago, after a period of warming. Over a few decades temperatures plummeted and life became very difficult for animals and man.

The North American continent took the brunt of the damage. In the Southwest of Washington state lie the Channelled scablands. Carved out of solid rock by cubic miles of melt water, these devastated lands are still mostly barren. Controversy surrounds the cause of these massive eroded cataracts and flood planes. A heated argument exists between catastrophists and those who favour a more gradual explanation.

Geologist J Harlen Bretz first proposed massive single floods as the cause of the scablands. In the 1920’s he calculated that 500 cubic miles of melt water would be required to create the kind of devastation seen. At the time he had no idea of the source of so much water.

The uniformitarian dogma, prevalent at the time, suggested several smaller floods over a long period, would cause the same damage. Bretz was pilloried until the 1980’s when evidence for a single flood began to mount up.

Climate freeze

Now to the freeze. In the North Atlantic warmer waters from the South transfer heat to the Northern hemisphere. This is known as the Atlantic meridional overturning circulation. As warm water from the tropics flows north it evaporates, this makes the water more salty, causing it to sink. As it sinks it begins to flow South again. Any disruption to this flow will cause a large drop in temperature.

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So what caused the disruption? As Bretz proposed, melt water did not just go South, over land. A mega-flood of fresh water was dumped into the North Atlantic stopping the flow of warm water from the South. At the time lake Missoula covered large parts of Canada, this lake was held in place by an ice-dam. Did the dam burst and if so why?

A tale of two theories

Two theories compete to explain the massive flooding. One involves a simple dam burst. The other postulates a comet impact. As the ice age warmed huge meltwater lakes formed. Lake Missoula covered 7.700 square kilometres and held 500 cubic miles of water. A massive wall of ice near Clarke fork Idaho held back this gigantic mass of water. In places it was 2000 feet high and under enormous pressure. This huge plug of ice was miles deep holding back the river and threatening disaster. Did a sudden collapse of this dam lead to the formation of the scablands? The second theory suggests that a massive comet broke up over the Northern Hemisphere. Several impacts caused devastating damage.

Other evidence, meteor fragments

The Inuit who are not strangers to ice are hunters and value highly any iron tipped weapons. Before the iron age this was very scarce, the only source being from Iron meteorites. So where did the Inuit find the iron? You won’t be surprised to learn that fragments of an iron meteorite were found in North West Greenland. The Inuit used them to make harpoon tips and tools. Is there other evidence of impact?

Comet theory

In 2008 a new proposal for the causes of the Younger Dryas, became prominent. A team led by Firestone and West suggested that several impacts from a fragmenting comet had hit the ice sheet.

This theory came from a group of highly accredited scientists who together stuck their necks out to bring it to the world. Richard Firestone is a nuclear analytical chemist at the Lawrence Berkeley National Laboratory in California. He pointed out the black mat layer, at several well dated Clovis sites and the presence of impact proxies such as melt-glass and nano diamonds.

“You might find some other explanation for these individually,” says Firestone, “but taken together, it’s pretty clear that there was an impact.” The team says the agent of destruction was probably a comet, since the key sediment layer lacks both the high nickel and iridium levels characteristic of asteroid impacts”

Where did this happen?

The highest concentration of debris is shown to be at the edge of the old ice cap. This lessens further south. So, the comet probably blew up over Canada.

Mass burning and floods caused an extinction level event that lasted for more than a thousand years. The only problem was… no crater. They suggested that impacts on ice would not leave any evidence, however 10 years later, has one of the craters has been found?

Another crater in Greenland? More recently another crater has been found in Greenland, this is though to be older than the one under the Hiawatha glacier, but who knows?

The black mat returns

The black mat that blankets North America contains substances that support the impact hypothesis. As a result of the impact 10 million tonnes of material was deposited across four continents. Carbon spherules are formed from melted rock, nano diamonds were also found. Both of these are indicative of a cosmic impact event of massive proportions.

Interlude #2

Huddled against it’s mother, the mammoth calf struggled against the hot wind. Fires crackled as the surrounding trees smouldered. Slowly, the stunned landscape began to darken. The thump, thump, thump of impacts shook the ground. Proudly, in a clearing stood the dominant male, his huge tusks raking the sky in anger. Suddenly, a noise like a thousand freight trains ripped the world apart. A huge wall of water crashed down on the helpless creatures below. Trees, rocks, broken ice and bodies swirled together. Jammed into caves, sometimes literally broken off at the ankles, the victims lie buried. Snow falls and a terrible winter reins for a thousand years.

Nuclear Winter

Less than 15,000 years ago an array of large animals roamed the lands of North America. Mammoths the size of a small car lived in their thousands. Beavers like giant machines dammed the rivers. Predators such as American lions, sabretooth cats and giant bears hunted in this verdant paradise. In a short time they were all to die in an unexplained cataclysm.

Move or die!

If the direct impact did not get you then the cold would. Maybe 10% of all the trees on Earth were on fire. Enough poisonous gasses filled the air to block the sun. The impact was so great that some rocks and ice fragments were blasted into orbit. These rained down as far as Europe and the Middle East. After the drama came the cold, the surface did not see sunlight again for many years. A nuclear winter enveloped the North. Most large animals in North America died, Africa faired better with large mammals like elephants and lions surviving.

How do we know what the ancient climate was like?

Ironically, the best way we know about the ancient climate is from the Greenland ice cores taken in the 1990’s!

The Greenland Ice project GRIP ran from 1989 to 1995. A core was taken that reached to the bedrock and revealed 100,000 years of climate history. Isotopes in the ice cores clearly show the sudden freeze at the beginning of the Younger Dryas. They also show the remarkably stable climate of the last 7,000 years.

How do we know what happened to the large animals?

There are two factors that track mega-fauna. Pollen records tell us the plant distribution and fossil records indicate the existence of large animals. During the Younger Dryas 50% of large animals disappeared in North America. At a site in South Dakota the Smithsonian says “Altogether, parts of 58 mammoths lie exposed in an area about the size of a hockey rink”. Supposedly the stupid Mammoths got stuck in a sink hole and died. Much more likely they were washed here by a mega flood.

Flooding and loss of land

During this terrible interregnum humans struggled to survive in a changed world. Spring did not arrive for another 1200 years.

Move away from the coast!

The archaeological record shows that there were three massive pulse floods during the great melt down at the end of the last ice age. Sea levels rose by 120 meters, drowning coastal areas. The drowning began 17,000 years ago and did not end until 7000 years ago. So that sounds fairly gradual, right? No! Bursting ice dams and comet impacts lead to sudden flooding at least three times. Many things were happening at once.

The world echoed and boomed as thousands of tonnes of ice melted. Areas under the ice rose as the weight lessened. Massive earthquakes shook the tortured ground. Ice core data shows that many more volcanos were active than before.

Twenty five million square KM of land were lost to the inexorable flooding. The three pulse floods were widely separated but one coincides with the Younger Dryas, about 12,000 years ago.

Interlude #3.

The tribe trudged south as the never ending night dragged on into a third month. Dust and ash hung in the air like a constant ache. Dead animals littered the blackening ground. Thin and gaunt the leader climbed onto a lichen covered boulder. Withered trees, like starving ghosts loomed out of the gloom. He cupped his ear and listened, a vast rushing sound could be heard, like a million Niagara falls. The ground shook and a desperate cry rang out. A hunger crazed lion was dragging off a small child.

There may be a deep racial memory of this terrible period. Is that why some academics suffer from catastrophobia?

The Younger dryas impact hypothesis

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