Geologist John Wesley Powell looks up at the cliffs that rise to the sky on both sides of the river. There is clearly something not quite right in these huge rocks.
The year is 1869 and Powell is on a research expedition through the unexplored areas of the southwestern United States.
Along with nine others, he sails the deadly Colorado River to explore and map this unexplored land. Before the end of this three-month journey, four expedition members have disappeared due to fear for their lives in the future. But Powell continues undeterred. He is making a remarkable discovery.
The river has led him into the formidable canyon, the Miklagil or Grand Canyon itself, and there you can clearly see the layers in the rocks. The earth’s layers were formed from sand, clay and lime, which since the infancy of plants have been layered on top of each other, thus preserving the remains of the world’s organisms for hundreds of millions of years.
But this archive of strata is not complete. Powell has discovered that there is a large part missing.
More than a billion years have passed – including when Earth’s first animals appeared.
Now, more than 150 years later, scientists know that Powell’s discovery has a counterpart on every continent, and that the missing part covers more than a billion years of Earth’s history, or the period from 1.8 billion years ago to about 600 million years ago – sort of.
But how did more than a billion years disappear from Earth’s history? Scientists have been studying this time theft ever since Powell’s day. However, it is only now that they believe they have found the culprit.
Covers the entire globe
It was the sharpness of Powell’s attention that made all the difference in his discovery.
Under normal conditions, strata are formed so that a new layer is placed on top of the existing one when sand, clay and lime form a new sedimentary layer. The layers of the earth initially lie mostly in the same direction, similar to a loaf of bread. In the course of time, the strata may start to tilt due to movements in the earth’s crust, but internally the continuity usually does not change.
In the Grand Canyon, the oldest clapboards had a steep slope, while the youngest ones were completely horizontal. It was also not the case that the deficit increased steadily, but a fairly rapid transition could be detected. It was precisely this that Powell found strange.
An even gradient change between the oldest and youngest layers should have been seen in many hundreds of meters of clapboard layers that would have formed over billions of years. But traces of such things seemed to have completely disappeared.
Powell called this “the Great Incongruity.” Since then, geologists have dated the clapper layers and can confirm that in some places 175 million years seem to be missing from Earth’s history, while in other places as much as 1.6 billion years.
What Powell didn’t know was that the “great dissonance” is found all over the globe. Only in a very few places have geologists found traces of this lost time and at the same time traces of one of the most significant events in Earth’s history, the appearance of the first animals.
Remains reveal major events
More than a billion years – the period from 1.8 to 0.6 billion years – has been erased from Earth’s history book. However, geologists have found some scattered remains, which provide insight into the missing years.
1.630 million years: A meteor hits Australia
The 30 km wide Shoemaker Crater in Western Australia is one of the very few meteorite craters from this period still in existence. The crater shows that a meteorite about a meter in diameter hit the Earth there 1.6 billion years ago.
1,500 million years: Fungi go their separate ways
Up to 3.8 million extant species of fungi were considered plants for a long time, but studies show that fungi are more closely related to animals. DNA analyzes show that the evolution of animals and fungi diverged 1.5 billion years ago.
1,100 million years: Magma boils in the USA
About 1.1 billion years ago, North America split in two due to glowing magma that melted the earth’s crust from below. The remains of the magma tunnels are still visible.
890 million years: First animals appear
The first animals undoubtedly evolved during this period. However, exactly when is not entirely certain. DNA analyzes of fossils show that it was between 650-890 million years ago and the first animals may have resembled sea sponges.
The time slot can be found on all continents, including the European one. There, the lower side of the Powell unconformity can be identified on flat and fractured bedrock in large parts of Sweden, Finland, Norway and northwestern Russia.
Everywhere, it is also roughly the same era of Earth’s history that has faded away – an era that began 1.5 to 2 billion years ago and ended 550 to 600 million years ago.
The result is that the scientists know next to nothing about what happened on the earth for nearly a quarter of its existence.
Solids dissolve away
Globally, there is an almost incomprehensible amount of rock layers that have been eroded away, and what caused this hole in Earth’s history must therefore have taken an enormous amount of time. The scientists have therefore been looking for a culprit that has been around for hundreds of millions of years.
The globe is constantly changing due to land drift. New oceans and new mountain ranges are constantly being formed, and only relatively few geological formations manage to stand undisturbed for very long.
However, scientists have managed to find a few major events that both happened at the right time and lasted long enough to break up the amount of rock needed to create this hole in Earth’s history – and at the same time steal our knowledge.
As the geologists collected more and more evidence, the anomalies appeared.
Among the possible culprits is the supercontinent Nuna – also called Columbia. Geologists still have very limited knowledge about Nuna, but this giant continent probably formed about 1.8 billion years ago and then held together for at least half a billion years, or about twice as long as any other giant continent.
Such a long life of a united continent has left all the dry land of the globe open to erosion long enough for winds and weather to have worn it down fairly evenly. If this is true, an enormous amount of rock has fallen from all the dry land of the globe.
This theory seemed promising at first; Among other things, the timing of the formation of the continent fits well with the beginning of the time fault discovered by Powell at the Colorado River. But as more information was collected, more anomalies also appeared.
A Chinese study from 2019 revealed that the breakdown of rocks in China did not begin until after the Nuna continent had broken up.
Destruction of bulldozer forces
The flaws in the Nuna theory led scientists to look for another possible culprit. Among other things, their attention is focused on a real giant of power that could easily remove a lot of rock from the surface of the earth in record time: the global ice age.
Ice in the form of a glacier cap is so thick and heavy that it can be compared to a viscous mass that crushes everything in its path. In this country, in many places you can see the traces of glaciers during the last ice age, which ended 11-12 thousand years ago, and in the northern part of Scandinavia, glaciers scraped massive amounts of material and moved south. This material now forms the lowlands of southern Sweden and Denmark.
During the global ice age, it can be said that all dry land is covered by glaciers and sheet ice covers all oceans.
On this planet, ice has covered the entire surface several times, but one such general ice age, called the Sturtian Ice Age, which began about 717 million years ago, has attracted special attention in this context. The ice became so great that at times about half of all water on earth was in frozen form.
However, the ice has covered almost the entire globe completely continuously. The climate has fluctuated between extreme cold and milder periods in between. But it wasn’t until about 660 million years ago that the ice completely melted.
Glaciers have thus had more than 55 million years to gnaw away at the dry land, giving enough time to create Powell’s fault, “the great unconformity”.
American geologist C. Brenhin Keller believes this ice age is the culprit. He believes that the Sturtian Ice Age scraped an average 1.6 km thick layer from all dry land and carried it out into the sea. In 2018, he set out to search for the remains of these ancient rocks with a group of his friends.
On the trail of the time thief
In the oceans, a new seabed is constantly formed when lava flows from the bowels of the earth and solidifies. At the same time, an old ocean floor disappears into the Earth’s mantle when crustal plates on the ocean floor are pushed under other crustal plates at plate junctions, which usually occur at the edges of continental plates.
If glaciers during the global ice age crushed rocks on dry land and transported them to the ocean, that crushing has long since disappeared into the depths of the mantle at plate junctions. C. Brenhin Keller knew, however, that this material is not lost forever.
Rocks usually contain zircon, which is extremely durable. When a rock subducts at a plate junction, it can melt and then rise to the sea floor again in volcanic eruptions – but the zircon crystals do not change.
Keller and his colleagues therefore studied precisely zircon – a total of 30,000 crystals – from all periods of Earth’s history. The zircons can testify to their origin because of the two elements they contain: hafnium and oxygen.
Both elements exist in different forms called isotopes. The ratio of the isotopes shows whether zircon is derived from the earth’s crust or has formed inside the globe.
Keller’s research showed that huge amounts of zircon – most likely from dry land – had landed on the sea floor during the Sturtian Ice Age.
The results indicated that glaciers were the main culprits regarding the disappearance of the rock layers.
However, other scientists are not so convinced and say that glaciers treat the bedrock badly, in some places they slide over the land without leaving much damage, but in other places they tear up a lot of rock.
Now, a new study by geologist Michael DeLucia seems to support this criticism. The study shows that the reddening of the surface began long before this great ice age.
Crystals point to a new villain
Michael DeLucia and his colleagues used a new method in 2018 when they analyzed rock formations in Missouri, USA. The conditions there were strikingly similar to those John Wesley Powell saw in the Grand Canyon.
There are 500 million year old rock layers on top of 1.4 billion year old rocks. Just like C. Brenhin Keller, DeLucia also studied zircon in the rock, but instead of hafnium and oxygen, he looked at helium.
In zircon crystals, uranium and thorium dissociate to form helium. If the crystal is at a great depth in the ground, the heat is high and helium escapes. If the rock on the surface grinds down, the zircon crystals come closer to the surface and at a lower temperature, so helium can no longer escape.
DeLucia used zircon crystals in different strata to show that the fault that started the Powell unconformity began operating 850 million years ago—about 80 million years before the Sturtian Ice Age.
In the area that is now Missouri in the USA, at that time and later, 6 km thick rock layers have disappeared.
This timing coincides with another major event in Earth’s history: the disintegration of the giant continent of Rodinia. DeLucia doesn’t think this is a coincidence at all.
Before a giant continent disintegrates, its central elevation rises greatly, and the higher the land rises, the faster it erodes.
Before this continent began to break apart, there should have been a significant degradation of its surface. But this explanation is not entirely sufficient either.
Everything works out
In Canada, geologist Colin Sturrock and his two colleagues have made a remarkable discovery . Sturrock says that the company’s research indicates that the causes of rock erosion in Canada are so-called mantle plumes.
These are hot bubbles from the mantle and can originate from a great depth, even from within the core at a depth of about 2,900 km. They can be hundreds of kilometers in diameter.
The high temperature causes the mass filling to be low, and as a result, these heat bubbles behave like corks that reach the surface. The mantle plumes press on the earth’s crust from below, causing the land to rise and at the same time become more vulnerable to erosion.
Mantle jets thus cause increased erosion – but the erosion will be localized but not evenly spread over the entire globe.
A giant magma bubble was an accomplice
650 million years ago, glowing hot magma lifted Canada’s dry land so high that erosion managed to remove at least three kilometers of the top layer.
Like Michael DeLucia, Sturrock used the helium content of zircon crystals to date the breakdown of the bedrock. The analysis showed that in Canada, these events occurred about 650 million years ago – that’s 200 million years later than the changes DeLucia found in Missouri.
Sturrock says the explanation lies in plain sight and that it can finally be used to connect all the evidence that people have seen working against each other: There was not just one culprit at work.
In Canada, mantle plumes were at work, in Missouri, the disintegration of the giant continent of Rodinia. Elsewhere, the Sturtian Ice Age or the long-lived supercontinent of Nuna may have been involved. What appears to have been one continuous event across the globe, Sturrock says, may just as well have been multiple major events that occurred in very different places and at different times.
This theory brilliantly explains why timing is not the same everywhere.
However, not all scientists are ready to let go of the theory that some single event is the main culprit.
They have already begun using DeLucia’s helium technology along with other methods to study places outside of North America and find new clues about the biggest time theft in Earth’s history – a theft case that began with the observations of John Wesley Powell in 1869.
The first animals have now been found
The animals appeared on the scene during the billion years that have been lost from Earth’s history. Now scientists have finally discovered our very first ancestors. Read the article here .
