What is an Ice Age? 

Generally speaking, ice ages are periods of time when the Polar Regions are covered in ice and continental glaciers are present. During these times, global temperatures drop and glaciers around the planet expand.  

The expansion happens in cycles, with temperatures dropping enough to prevent snowfall from melting fully, which then turns to ice, and the process continues each subsequent snowfall. Ice ages can last thousands or even millions of years, and sometimes bring with them extremely harsh climatic conditions.

What are Glacial and Interglacial Periods? 

• Interglacial Periods 

Within ice ages there are intervals of warming and cooling periods known as glacial and interglacial periods. The warming episodes are known as interglacial periods, characterized by warmer temperatures and contracting ice sheets. Our most recent substantial interglacial period began 11,600 years ago at the end of the Younger Dryas.  

• Glacial Periods 

On the other hand, glacial periods correspond with cooler temperatures and a general expansion of glaciers and ice sheets worldwide. The last large glacial period on earth peaked around 18,000 years ago, in which time there was an ice sheet covering all of Canada and the Northern United States, as well as Siberia, the UK and Western Europe.  

It is now known that between 1450 and 1850 AD the earth dipped into what is known as ‘the little ice age’, which was actually a brief glacial period. This is known historically as the Dark Ages, and had profound implications for life on earth. 

When did the last ice age begin and end? 

The Pleistocene Era is typically defined as the time period that began about 2.6 million years ago and lasted until about 11,700 years ago.  

What happened to sea levels during the last ice age? 

During an ice age, huge changes in the Earth’s surface occur. As glaciers expand they erode hills and mountains, as well as carrying huge amounts of sediment and boulders, almost like a bulldozer destroying everything in its path, resulting in the total reshaping of entire landscapes.  

Ice ages also bring with them lower sea levels, as the ice accumulating is drawn from the water in the atmosphere which is sourced from lakes, rivers and oceans. As this occurs, massive expanses of new land are exposed, changing the appearance of areas dramatically. Imagine waking up one day to find a flowing river near your house had become an inland lake! 

As ice accumulates during an ice age it is unbelievably heavy, this can cause isotactic depression in the Earth’s crust; literally the squashing of the Earth’s crust in a way similar to sitting on a cushion.  

As this is happening, land on other parts of the crust are pushed up, meaning new islands can rise from the sea or land already exposed will grow upwards. As the ice melts this process is reversed, as it does when you get off the cushion, slowly expanding to its original, natural position. 

What are the five ice ages?

 The Earth has experienced as many as five great ice ages in its past. 

1. The earliest recorded ice age is known as the Huronian, spanning from 2.4-2.1 billion years ago. 
2. Cryogenian (850-625 million years ago),  
3. Andean-Saharan (460-430 million years ago) 
4. Karoo, which began 360 million years ago and lasted for 100 million years. 
5. The Quaternary, which we are still in the midst of, began 2.6 million years ago. 

What Triggers These Earth Periods? 

There are several theories on what contributes to the onset of ice ages, as well as interglacial and glacial periods, with no consensus amongst scientists as to the main cause.  

It is thought to be a highly complex equation with lots of moving parts: volcanic activity, sea currents, cosmic impacts, solar radiation, greenhouse gas emissions, and human interference are all thought to be pieces in the puzzle. 

•  Solar Cycles 

The amount of solar radiation the earth receives from the sun is the main driver for global temperature, and this change in cycles depends on our solar system’s position in the galaxy. These cycles, known as ‘Milankovitch Cycles,’ were first discovered by the Serbian mathematician and astronomer Milutin Milankovitch, who concluded there are three main factors that influence Earth’s climate; eccentricity; precession of the equinoxes; and axial tilt. 

• Earth’s orbit 

The Earth’s revolution around the sun varies slightly from a circular orbit to a slightly elliptical one in a cycle that lasts around 100,000 years. When eccentricity is high, a more elliptical orbit is underway. This leads to a greater length of time between autumnal and vernal equinoxes in each hemisphere. 

 It is at this time that seasonal temperatures fluctuate by around 20-30%. When eccentricity is low and our orbit is relatively circular, Earth is closer to the sun. This means that seasonal temperatures don’t fluctuate as much and things are more predictable as the Earth receives a relatively constant amount of solar radiation throughout the year. 

• Axial Tilt 

The Earth doesn’t spin perfectly upright on its axis, it does so on a slight tilt. Over a 41,000 year cycle, this moves from 22.1 to 24.5 degrees. Depending on the axial tilt relative to the orbital plane, Earth will experience different temperatures and seasonal variations. The larger the tilt, the larger the variations will be, and vice versa. It is now thought that a smaller axial tilt results in milder winters and cooler summers, implying that glaciations are more prominent during these times. 

• Precession of the Equinoxes 

Along with eccentricity and axial tilt, the precession of the equinoxes is another factor in the Milankovitch Cycle. This is because the Earth has a slight bulge in the equator; it wobbles like a spinning top.  

Because this bulge is on a different plane to Earth’s orbit around the sun, gravity from other bodies in space affect the Earth in such a way that it adopts this wobble. A full precessional cycle takes around 25,920 years to complete.  

Conclusion 

Ice ages have shaped earth periods throughout the history of our planet. What causes them isn’t exactly understood as yet.  

As all of these cycles play out, complex climatic effects are felt on Earth. Each individual aspect can alter the amount of solar radiation the Earth receives. Yet as the combination of tilt, eccentricity, and precession play out together, the earth can be affected in very complex and complicated ways.  

Now it’s up to you, how do you think ice ages, and interglacial periods shape life on earth and human history?  

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In the last 20 years, researchers have been following the scent of a planet-wide mystery. The trail of a disaster and extinction event at the end of the last ice age, when human civilization arose. In geological terms, it is a blink of an eyelid, yet we know less  of the time than the dinosaur extinction. For nearly a century, researchers across many disciplines have been piecing the story together. Science takes times to build evidence. When the penny drops, it spreads like a comet striking the conscious minds of humanity.

Around 12800 years ago the world caught on fire. New research published in the Journal of Geology has revealed 30 million square miles of earth burnt during this time. That is roughly 10% of the total biomass on the planet. The Younger Dryas impact hypothesis is one explanation for the findings.

On its own, you may think, well so what? However, the study sits in a body of evidence that describes a period in earth’s climate that was like no other. 12 800 years ago, the North American ice-sheet vanished. It caused the great flood, intense periods of global warming and cooling, megafauna extinction, and human population decline.

The earth was like the scene of a crime. Evidence lay dotted and spread, wiped clean by the nature of its own ferocity. 12 000 years later, the offender is coming forward.

The Younger Dryas Impact hypothesis describes a possible cause for the cataclysmic scenario. In this article, we will explore the evidence that the earth was the victim of a very recent and life-shaking cosmic impact.

The Prehistoric end of the Ice-Age and the great flood

The Younger Dryas was a period that lasted from 12 800 – 11 600 years ago. It happened as the earth was exiting the last glacial maximum. Ice-sheets covered most of North America and some of Europe. Sea-levels were 400ft lower exposing land mass the size of China and Europe together.

Earth was slowly warming, and then, without warning, it was thrown back into ice-age conditions. Temperature drops of 10 degrees happened in a period of ten years. The North American ice-sheet melted so rapidly that it caused the great flood.

Sea levels rise of 400ft happened globally. The geology of the US now bears the scar of the floodwaters.

The Younger Dryas lasted 1200 years long before an intense global warming event of 10-15 degrees. During this time human populations were severely affected. The North American Clovis Culture vanished, and 75% or 120 species of the US megafauna experienced a mass extinction event.

Each of these stories, when viewed on their own don’t mean a lot. Put them together, though, and the Younger Dryas impact satisfies the criteria to explain the planet-wide conditions.

What caused the Younger Dryas?

The Younger Dryas impact hypothesis was first proposed just ten years ago. It was ridiculed due to lack of evidence, in particular, a smoking gun, or an impact crater.

The theory suggests a comet impact 12800 years ago destroyed the North American Ice sheet and set off global wildfires. As a result, periods of extreme climate change devastated the planet alongside human and animal populations.

A group of scientists named The Comet Research group have led the way to understand the period. They have proposed that around 12 800 years ago, a giant comet entered the solar system and began an Earth-crossing orbit.

The comet is said to have then broken up into fragments and entered the earth’s atmosphere. One and maybe even multiple fragments of the comet hit the earth and caused a worldwide catastrophe.

Estimates suggest the comet was a colossal 60 miles in diameter. An impact with an object of that size today would send human civilization back into the Stone Age. Alternatively, perhaps, extinction.

If the impact did happen, it shakes the very foundation of our history as a species on earth. At a time when modern civilization arose, the Younger Dryas is a critical period for the human origin story.

At the very least, the impact hypothesis needs to be heard.

The Comet Research Group

A team over 50 scientists are compiling evidence from all over the world. Their mission is to confirm, through evidence, that it was indeed a comet that struck the earth 12800 years ago.

The issue is that comet impacts are difficult to prove. Scientists that work in the field must fulfil strict criteria to prove an impact crater.

The idea should not seem too far-fetched. It was only just over 100 years ago that an object from outer space hit the earth and caused a localized catastrophe.

In 1908 a relatively small meteorite exploded in the atmosphere in Tunguska, Siberia. Luckily it happened over forestland and not a city, where 80 million trees were wiped from the earth.

If the Tunguska event occurred slightly later over Europe, it would have re-written human history.

How the dinosaur extinction happened

 It is ironic we know more about the dinosaur extinction of 65 million years ago than we do about the events of the Younger Dryas.

While it’s common knowledge today, the dinosaur impact took decades to prove. Once the first fossil was found many theories surfaced of how the mega-beasts declined. It took the impact crater to be located in the Gulf of Mexico to reveal one of the biggest extinction events of early earth history.

The idea of an asteroid wiping the dinosaurs out was met with strong skepticism. Then iridium-rich layers 30 times the amount average in the Cretaceous/Tertiary (KT) boundary began appearing. It wasn’t until the impact crater appeared that the impact theory was accepted.

Today a similar growth in evidence is happening for the Younger Dryas impact.

Did a comet cause the Younger Dryas?

‘Impact proxies’ are the evidence that suggests impact events. Think of them like fingerprints of an outer space object.

If they can be confirmed from outer space, they can be dated to time depending on their surroundings.

Let’s look at 8 Impact Proxies for the Younger Dryas Impact Hypothesis.

1. Global Wildfires

The most recent study shows 10% of all biomass burning around the Younger Dryas period. It doesn’t prove an impact on its own, it does build a strong case for a context of cataclysm.

 2. Platinum layer

Sites tested for platinum deposits in the US. Source

One of the first lines of evidence was when archaeologists discovered a platinum layer dating to the Younger Dryas. Platinum is an element most often found in meteors.

The strange layer of platinum, dated to 12 800 years ago, is found at sites all over the world. In the Northern Hemisphere alone, 26 documented sites have so far shown a platinum-rich layer. Other sites include North America, Greenland, Russia, The Netherlands, Lithuania, Belgium, and the French Italian border.

3. Melt-glass

A team of international researches studying melt-glass finds in Pennsylvania, South Carolina, and Syria. The 18-member team has discovered the thin glass layer dating to roughly 13,000 years ago.

Melt glass is only formed under intense amounts of pressure or heat. It requires temperatures between 1700 and 2200 Celsius. These conditions are equal to that of an atomic bomb.

The layers match the melt-glass found after the 1945 nuclear bomb test in Socorro, New Mexico. Nuclear bombs generate enough heat generated to make sand not only melt, but also boil.

4. Micro Spherules

Unexplained deposits of microspherules have been found across North America. They are also found across 18 sites in 9 countries. Dating has pointed them to the Younger Dryas. The samples share impact proxies including nano-diamonds, melt-glass, iridium, and buckminsterfullerenes. Together these elements provide strong suggestions of origins from outer space.

5. Carbon Spherules

Carbon spherules have been found in so Sheridan cave in Wyandot County, Ohio. Formed under intense heat, they are basically melted rock. Spherules are formed by lightning, forest fires, or burning coal. However, the spherules found here have been established to be due to combusted rock

These date to roughly 13,000 years ago, right at the start of the Younger Dryas period. The same spherules were also found at 17 other sites around the world, across four continents over an estimated area of 30 million square miles.

6. Sediment layer

In the floor of Lake Cuitzeo, Mexico a dark thin sediment layer was found. After analysis, it was found to contain an exotic collection of materials.

These included nano-diamonds and impact spherules, which, when found together are the result of a cosmic impact on the earth.

Appearing in the same layer, were spherules that had collided with others at extremely high speeds. These markers imply a chaotic and volatile event.

7. Mammoth tusks pelted with meteor

Megafauna populations are known to crash at 10 000 years ago. However, some studies have found tusks pelted with meteors. The dating is controversial, some saying they date to roughly 13 000 years ago, others saying the fossils are much older.

8. The impact crater

For the most part, an impact site is not been located. One theory explains that the major impact occurred across the top of North American ice sheet itself. The glacier was so thick that such an event could be devoid of a crater site.

Most recently, scientists have discovered a 31 km wide-impact crater beneath the Hiawatha glacier in Greenland.

It was found  using airborne radar surveys which unveiled a circular bedrock depression beneath the ice

The impact was most likely made by an iron meteorite more than 1 km wide. Some have suggested it dates to 12 000 years. However a sub-glacial crater has never been found before, so exact times are difficult to ascertain.

While not proving it, the Hiawatha crater certainly adds credence to the Younger Dryas Comet hypothesis.

The Hiawatha crater could date to the Younger Dryas comet period.

Conclusion

The cause of the Younger Dryas could become a crucial scientific discovery of the 21^st century. Today the evidence is irrefutable that human ancestors survived a harrowing period to live on earth.

The mystery is compounded by the destructive nature of the Younger Dryas. Evidence would be wiped clean from the earth or submerged beneath the rising seas.

While researchers have not confirmed an impact, the clues are pointing to something of cosmic origin.

We will be following the Younger Dryas Impact Hypothesis.

If you have anything to add to this article, please leave it in the comment section below.

To learn more about the comet research group, or donate to help their research, please click here.

Further reading:

1. https://www.ncbi.nlm.nih.gov/pubmed/23878232
2. https://www.ncbi.nlm.nih.gov/pubmed/17901202
3. https://www.nature.com/articles/srep44031
4. https://www-journals-uchicago-edu.ezproxy1.library.usyd.edu.au/doi/10.1086/695704
5. http://advances.sciencemag.org/content/4/11/eaar8173.full

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