36-million-year tectonic cycles power Earth's biodiversity, finds study

The cycles, which go back at least 250 million years, challenge beliefs on species' long-term evolution.
Sade Agard
Gondwana Stars Observatory, Australia
Gondwana Stars Observatory, Australia

University of Sydney/ Steve Lippis 

The movement of the Earth's tectonic plates plays a crucial role in triggering bursts of biodiversity in 36-million-year cycles, according to a new study published in PNAS on July 10. 

The cycles, which go back at least 250 million years, could represent a significant challenge to common beliefs about the long-term evolution of species.

The 36-million-year cycle

"In terms of tectonics, the 36-million-year cycle marks alterations between faster and slower seafloor spreading, leading to cyclical depth changes in ocean basins and the tectonic transfer of water into the deep Earth," explained Professor Dietmar Müller, co-author of the study from the School of Geosciences at the University of Sydney, in a press release

"These, in turn, have led to fluctuations in the flooding and drying up of continents, with periods of extensive shallow seas fostering biodiversity."

36-million-year tectonic cycles power Earth's biodiversity, finds study
Global map of Earth's tectonic plates and their boundaries.

This phenomenon occurs as sea levels rise and fall, causing the expansion and contraction of different habitats on continental shelves and shallow seas. 

Such environmental changes allow organisms opportunities to flourish or perish, leading to the emergence of new life forms as observed in the fossil record.

The team's findings relied on the GPlates plate tectonic software developed by the EarthByte Group at the University of Sydney.

The research team discovered remarkably consistent cycles by analyzing sea-level variations, Earth's internal mechanisms, and marine fossil records. 

They amassed compelling evidence supporting the critical role of tectonic processes and global sea-level changes, driven by the dynamic forces of the Earth, in shaping marine biodiversity over vast timescales.

"The cycles are 36 million years long because of 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," highlighted Professor Müller.

Additionally, he emphasizes that this research challenges previous ideas about the long-term evolution of species.

The Cretaceous Winton Formation in Queensland, known for its dinosaur fossils and precious opal, serves as a prime example of how sea-level changes have influenced ecosystems and biodiversity in Australia. 

As the continent experienced rising and falling sea levels, diverse ecological niches formed in the expanding and contracting shallow seas, providing unique habitats for various species.

"The Cretaceous Winton Formation stands as a testament to the profound impact of these sea-level changes, capturing a snapshot of a time when Australia's landscape was transformed, and fascinating creatures roamed the land," Professor Müller concluded.

The complete study was published in the Proceedings of the National Academy of Sciences (PNAS) on July 10 and can be found here.