Ziyi Zhu of the Australian National University (ANU) had no idea that her research would lead to the discovery of a mega-geographical structure that once dominated the surface of our planet and led to the evolution of life as we know it today. Dubbed supermountains, this chain of hills spanned across continents and led to the emergence of the first macroscopic organisms.
A Ph.D. candidate at ANU, Ziyi says that it all started when one of her collaborators from the Queensland University of Technology spotted peculiar traces of minerals known as zircons in samples collected from eroded roots of mountains. Zircons are often termed as ‘time capsules’; they are minerals that are known to retain chemical fingerprints of the era to which they belong.
“I then searched for the geological meaning of these low-Lu Zircons and found their connection with supermountains. The finding of the link between supermountains and biological evolution was also unexpected. It was about one and a half years ago when I happened to read a paper about the changes in the maximum size of life through time, which then turned out to fit my supermountain theory well,” Ziyi told IndiaToday.in.
Ziyi and her fellow researchers published their findings in the journal Earth and Planetary Science Letters revealing that these supermountains took shape twice in the short history of Earth.
The Himalayan Mountain Range runs a curving path from west to east in this true-color Terra MODIS image. (Photo: Nasa)
HOW DID THESE SUPERMOUNTAIN FORM?
The Himalayan ranges that span 2,300 kilometers in length would be just one-fourth of these unique features that extended for over 8,000 kilometers, nearly 2000 million years ago. Ziyi says that the origin of these supermountains is largely similar to how the Himalayas formed about 50 million years ago due to a collision between the Asian continental plate and the Indian plate. “These supermountains too formed when two continents collided,” she added.
They formed twice in Earth’s history — the first time between 2,000 and 1,800 million years ago and the second between 650 and 500 million years ago. Researchers believe that there are links between these two instances of supermountains and two of the most important periods of evolution in Earth’s history.
The first supermountains are being called Nuna Supermountain, which coincides with the likely appearance of eukaryotes, organisms that later gave rise to plants and animals. The second structure that evolved around 650 and 500 million years ago is the Transgondwanan Supermountain, which coincides with the appearance of the first large animals and the Cambrian explosion 45 million years later, when most animal groups started appearing in the fossil records.
The Himalayan ranges as seen from space. (Photo: Nasa)
HOW DID EARTH LOSE ITS SUPERMOUNTAINS?
The loss of these mountains was not a sudden event. High mountains are exposed to strong winds, rain, and ice, all of which lead to small pieces of rocks breaking off, a process that’s called weathering. Once a rock has been broken down, a process called erosion transports the minerals into the oceans.
Once these supermountains were gone, the continent became relatively flat, which slowed down the process of erosion. The slowing down of weathering and erosion caused a major decline in the supply of nutrients to the oceans.
“The slowed erosion rates would then reduce the supply of nutrients to the oceans, and therefore limit biological productivity. In a more specific sense, biological organisms during that time may have insufficient nutrients to grow more and grow larger,” Ziyi Zhu said.
Researchers believe that there are links between these two instances of supermountains and the two most important periods of evolution in Earth’s history. (Photo: Nasa)
WILL THERE BE SUPERMOUNTAINS IN THE FUTURE?
With climate change and global warming affecting mountain ranges across the world, geologists have found evidence suggesting that a new supercontinent named Amasia will form in the next few hundred million years when Asia will crash into the Americas, and Australia will slam into southeastern Asia.
“In such a scenario, extensive high mountains (supermountains) would be able to form (again) when many plates collide with each other,” Ziyi Zhu told indiatoday.in.
The new discovery is key to understanding the evolutionary process that a young planet went through and could provide information that could help in saving the mountains of today.