Tectonic changes can alter sea level, creating an environment for life to reproduce. The researchers found that the movements of Earth’s tectonic plates cause sea levels to rise and fall in 36-million-year cycles, which indirectly causes spikes in biodiversity. These cycles, which alter shallow marine and shelf habitats, have been found to significantly shaped the diversity of marine life over millions of years, challenging previous concepts of species evolution.

New research has shown that the movement of Earth’s tectonic plates causes sea levels to rise and fall, indirectly causing spikes in biodiversity over 36-million-year cycles. Researchers, including geologists from the University of Sydney, believe these geologically driven cycles of sea level change have had a significant impact on marine species diversity since at least 250 million years ago.

As water levels rise and fall, different habitats on the continental shelves and shallow seas expand and contract, creating opportunities for organisms to thrive or die. Scientists studying the fossil record have shown that these shifts gave rise to new life.

The study was published July 10 in the journal Proceedings of the National Academy of Sciences Led by Associate Professor Slah Bulila of the Sorbonne University in Paris.

250-million-year reconstruction of Earth’s geography showing the interaction between plate tectonics and sea-level fluctuations. Credits: Paleomap Project and Michael Chin

Professor Dietmar Müller, from the University of Sydney’s School of Geosciences, said: “From a tectonic perspective, the 36-million-year cycle marks changes between faster and slower seafloor spreading, resulting in cyclical changes in ocean depth in basins and in the tectonic transfer of water to the depths of the Earth.

“This in turn has led to fluctuations in flooding and drying up of continents, with periods of large shallow seas supporting biodiversity. “This work was made possible thanks to the tectonic plate software GPlates, developed by the EarthByte group at the University of Sydney and supported by Australia’s National Collaborative Research Infrastructure Strategy (NCRIS) through AuScope.”

The team based their findings on the discovery of strikingly similar sea level fluctuation cycles, Earth’s internal mechanisms, and marine fossils. Scientists now have convincing evidence that tectonic cycles and global sea level changes caused by Earth dynamics played a critical role in shaping the biodiversity of marine life over millions of years.

“This work challenges previous ideas about why species change over time,” said Professor Müller.

“These cycles take 36 million years because of the regular patterns of how tectonic plates are recycled back into the convective mantle, the moving part of the deep Earth, like a hot, thick soup in a slow-moving saucepan.”

Professor Muller said the Winton Cretaceous Formation in Queensland is a prime example of how changes in sea level have shaped ecosystems and impacted biodiversity in Australia. Known for its dinosaur fossils and valuable opal collection, the formation provides a valuable window into a period when much of the Australian continent was submerged.

As sea levels rise and fall, the continent’s flooding has created ecological depressions that widen and contracted in shallow seas, creating unique habitats for a wide variety of species. Source