They might have been the largest mountains our planet has ever seen.
These mountain majesties went above and beyond the fruited plain. Not only that, but they could have been quite fruitful in providing elemental building blocks that triggered the evolution of life on Earth.
As many as two billion years ago, mountain ranges may have stood taller than the Himalayas and stretched as far as 5,000 miles. And this wasn’t a fluke of history. After eroding, they formed once more in an era closer to ours, this time around 500 million years ago, give or take 150 million years.
Your car wouldn’t have been able to climb these mountains, and their place in history is beyond the stuff of bumper stickers. Their possible foundational role in geography and biology has scientists enthusiastically cutting a trail of research that includes a recent study examining the formation of these “supermountains.”
As we learn more about their significance, the supermountains are a reminder that the countless pieces of our natural world often fit into a jigsaw puzzle that shows us where we are and how we came to be.
How Big and Small Mountains Form
From Mt. Wycheproof (which is believed to be the world’s smallest mountain at 486 feet above sea level but only 141 feet above the surrounding terrain of Victoria, Australia) to Mt. Everest, the world’s tallest peak at 29,029 feet above sea level, most mountains were formed by plate tectonics.
As the University of California Museum of Paleontology explains, the collisions of continents produce the longest mountain ranges. The Himalayas came about after the butting of the Indian subcontinent into Asia. They also form when a tectonic plate rides over another, such as when the South American plate went on top of the Nazca plate and created the Andes. A series of somewhat parallel mountain ranges forms due to the thinning of thick continental cracks. Eventually, creation ends, and demise begins. After a relatively rapid rise, mountains are slowly shaped and reduced by sedimentation and gradual erosion.
The largest mountains of them all, the “supermountains,” seemingly formed in much the same way that smaller mountains have, except for one difference. The mountains were “super” because they arrived at a time when continents were smashing into each other to create supercontinents, and big mountains were apparently a byproduct.
What Goes Up Eventually Erodes
The new study’s authors from Australian National University (ANU) tracked the formation of the supermountains by looking at the minerals their peaks had left behind in Earth’s crust. The key mineral was zircon, a source of the metal zirconium, with a low content of lutetium. It is resistant to corrosion and has staying power through millennia. As the researchers outlined in a press release highlighting the study*, this combination of mineral and rare earth element is only found in the roots of high mountains formed under intense pressure.
The largest of the supermountains formed only twice in history, with the first arising between 2,000 and 1,800 billion years ago and the second between 650 and 500 million years ago. “If you can imagine the (1,491-mile long) Himalayas repeated three or four times, you get an idea of the scale,” the study’s lead author, Ziyi Zhu, said in the press release.
But size isn’t the only remarkable thing about the supermountains, according to Zhu and her colleagues. What’s just as amazing is the links between the supermountains’ existence and two important evolutionary periods. The erosion and sedimentation on these super mountain ranges, the researchers assert, have a strong connection to the evolution of life on Earth.
The Supermountains Could Have Started Life
As Zhu explains: “We call the (earliest) example the Nuna Supermountain. It coincides with the likely appearance of eukaryotes, organisms that later gave rise to plants and animals. The second, known as the Transgondwanan Supermountain, coincides with the appearance of the first large animals 575 million years ago and the Cambrian explosion 45 million years later, when most animal groups appeared in the fossil record.”
When the supermountains eroded, they supplied nutrients like phosphorus and iron to oceans. This transfer “supercharged” biological cycles and pushed evolution to stages of greater complexity, the researchers say. The supermountains could have also increased oxygen levels in the atmosphere, allowing complex life to breathe.
“The early Earth’s atmosphere contained almost no oxygen. Atmospheric oxygen levels are thought to have increased in a series of steps, two of which coincide with the supermountains,” Zhu said. Erosion of the Transgondwanan Supermountain is associated with the largest increase in oxygen in the planet’s history, which was a key precondition for the appearance of animals.
When viewed through the lens of the supermountains, the period between Nuna and Transgondwanan, which occurred between 1.8 and 0.8 billion years ago and was known as the “Boring Billion,” wasn’t exactly boring.
As Space.com notes, some scientists have theorized that the lack of new mountain formation during this era could have prevented new nutrients from leaking into oceans, starving sea creatures and stalling their evolution. That’s depressing for sea life, but the stagnation of that time supports the idea of a fireworks show during the two supermountain eras. It’s the deprivation of those “boring” years that affirms the flourishing of life during the time of Nuna and Transgondwanan.
“What’s stunning is the entire record of mountain building through time is so clear,” said another of the researchers, ANU Professor Jochen Brocks. “It shows these two huge spikes: One is linked to the emergence of animals, and the other to the emergence of complex big cells.”
Not Ironclad Research, but There’s Plenty of Data
Alan Collins, a geologist at the University of Adelaide who was not involved in this study, told Cosmos that the conclusions the ANU researchers reached by examining zircon with a low content of lutetium is “quite a long logic train, and it is controversial.”
The ANU researchers contend that the zircons are depleted in lutetium because of the environment in which they were formed: a high-pressure “soup” of magma beneath a volcano in a mountain range. Collins argues that those depletions could have come about in other ways, but he adds that, “We’re getting into a world where we’re getting an awful lot of data. We’re starting to be able to really treat these things in quite rigorous statistical ways to look for these trends.” Even though Collins seems skeptical, he does note that the ANU researchers conducted their work in a careful and logical way.
Just as time was on the side of creation during the Nuna and Transgondwanan eras, it may also benefit contemporary scientists who are looking at how the supermountains arrived and what they meant for life as we know it today.
“Once you can start to map out where these mountains are,” Collins said, “you can start to actually put them into the global climate models we use today and try and build that back in time.”
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* This press release erroneously gives the oldest mountain’s age in millions of years. The correct timescale is billions of years.