The belief that Earth is alive and kicking has received a robust boost with new research making a stunning discovery.
Just like human beings and other living organisms have biological clocks that govern their day-to-day lives, Earth has a geological clock of its own. And this clock governs the biodiversity that exists in any given period. This means that the human beings (the age of human life – estimated to be 2,00,000-years-old – is just a tiny fraction compared to Earth's geological age) who "rule" the world today may be just a passing species in the life of our 4.54 billion-years-old planet.
Scientists have discovered that Earth has geological cyclical patterns that have a bearing on changes in global biodiversity – and each of these cycles lasts for 36 million years. What's more, these cycles have been going on for the past 250 million years since life, as we know it, began in the ocean.
The new discovery by scientists from the School of Geosciences at the University of Sydney and Sorbonne University in Paris, is based on evidence that tectonic cycles and global sea level change driven by Earth's dynamics have played a crucial role in shaping the biodiversity of marine life over millions of years.
The researchers found that each of these cycles, which involve tectonic changes, alter sea levels that can create breeding grounds for new forms of life. They found that as water levels rise and fall due to shifts in tectonic plates, different habitats on the continental shelves and in shallow seas expand and contract, providing opportunities for organisms to thrive or die.
The geoscientists based their findings on studying cycles in sea-level variations and Earth's interior mechanisms, and comparing and correlating these studies with fossil records of past species. They found that these shifts trigger bursts of new life to emerge. The fossil records indicated existence or extinction of particular species corresponding to particular cycles, determining the birth or death of the species, with geological changes playing an active role.
Professor Dietmar Müller, co-author of the study, which has been published in the journal Proceedings of the National Academy of Sciences, explains that tectonics in each of these 36 million year cycles determine faster or slower seafloor spreading, which effect depth changes in ocean basins and transfer of water into deep earth. This causes drying up and flooding of continents, the shallow seas fostering biodiversity.
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Müller explains that the cycles are 36 million years-long due to regular patterns in how tectonic plates are recycled into the convecting mantle, the mobile part of the deep Earth, "similar to hot, thick soup in a pot that moves slowly."
QUEENSLAND'S WINTON FORMATION, AN EXAMPLE
The geoscientists cite the example of the 95-million year-old Cretaceous Winton Formation in central-western Queensland, Australia, as an example of a product of Earth's newly discovered 36-million-year-cycles, and how sea-level changes shaped ecosystems and influenced biodiversity in Australia.
This region is renowned for dinosaur fossils and precious opal, and is an ideal window into the prehistoric era when the Australian continent was flooded, and when the floods receded. The region is filled with sand and silt deposited by water bodies left behind by the retreating sea, to provide unique habitats for a range of species, including the dinosaurs. This happened because when sea levels rose and fell, it caused expansion and contraction of the ecological processes in the shallow seas, which provided new habitats for a range of species to thrive.