Australian geologists have recently conducted a study using plate tectonic modeling to uncover the cause of an extreme ice-age climate that occurred more than 700 million years ago. This research, published in Geology, not only sheds light on the Earth’s built-in thermostat but also highlights the sensitivity of global climate to atmospheric carbon concentration.
Unraveling the Mystery of the Ancient Ice Age
The study, led by ARC Future Fellow Dr. Adriana Dutkiewicz, addresses the long-standing question of what caused the planet to be nearly frozen in ice over 700 million years ago. The team proposes that historically low volcanic carbon dioxide emissions, coupled with the weathering of a large pile of volcanic rocks in what is now Canada, played a significant role in this drastic cooling event.
The inspiration for this research stemmed from the discovery of glacial debris in the Flinders Ranges in South Australia, which dates back to the ancient ice-age period. Guided by co-author Professor Alan Collins from the University of Adelaide, the team utilized computer models from the University of Sydney to analyze the cause and duration of this extended glaciation period.
The Sturtian glaciation, as it is known, lasted an astonishing 57 million years. This lengthy duration is baffling and difficult for humans to comprehend, as it predates the existence of complex plant life and dinosaurs on land. While various causes have been proposed for the start and end of this ice age, understanding its exceptional duration remains a mystery.
To unravel this enigma, the researchers turned to a plate tectonic model that traces the evolution of continents and ocean basins after the breakup of the ancient supercontinent Rodina. By connecting this model with a computer program that calculates carbon dioxide degassing from underwater volcanoes along mid-ocean ridges, they made a remarkable discovery.
The start of the Sturtian ice age coincided precisely with a period of remarkably low volcanic carbon dioxide emissions. Furthermore, throughout the ice-age duration, the outflux of carbon dioxide remained relatively low. This finding indicates that geological processes, specifically volcanic degassing and silicate rock weathering, heavily influenced the greenhouse gas concentration and played a significant role in triggering glaciation.
Plate Tectonic Reorganization and Continental Volcanic Province
Co-author Professor Dietmar Müller from the University of Sydney explains that the Sturtian ice age was likely caused by a combination of factors. Plate tectonic reorganization led to a minimum in volcanic degassing, while simultaneously, the erosion of a continental volcanic province in Canada consumed atmospheric carbon dioxide. Consequently, the atmospheric CO2 level fell below 200 parts per million, less than half of today’s level, triggering the onset of glaciation.
Implications for the Future
This study raises intriguing questions about the Earth’s long-term climate evolution. While a recent theory proposes that the Earth will eventually evolve into a supercontinent called Pangea Ultima, which could be so hot that mammals become extinct, the current trajectory of the planet suggests otherwise. With decreasing volcanic carbon dioxide emissions and the slowing down of tectonic plates due to continental collisions, it is possible that Pangea Ultima may instead experience another ice age.
The research conducted by Australian geologists provides insights into the causes and dynamics of an ancient ice age that occurred over 700 million years ago. By utilizing plate tectonic modeling and analyzing volcanic carbon dioxide emissions, the team has enhanced our understanding of Earth’s climate system. This study serves as a reminder of the gradual nature of geological climate change and its long-term implications for our planet’s future.