Discovering the Mysteries of Earth’s Ancient Ice Age
In a recent study published in Geology, Australian geologists have employed plate tectonic modeling to unveil the long-standing puzzle of an extreme ice-age climate that enveloped Earth more than 700 million years ago. Led by ARC Future Fellow Dr Adriana Dutkiewicz, the research sheds light on the intricate dynamics of Earth’s built-in thermostat, emphasizing the role of historically low volcanic carbon dioxide emissions and the weathering of vast volcanic rock deposits in what is now Canada. The findings not only enhance our understanding of Earth’s ancient climate but also underscore the planet’s sensitivity to atmospheric carbon concentration.
“Imagine the Earth almost completely frozen over,” remarked Dr Dutkiewicz, the study’s lead author. The research team delved into the enigma of the Sturtian glaciation, an extended ice age that persisted from 717 to 660 million years ago, predating the existence of dinosaurs and complex terrestrial plant life. The study was sparked by glacial debris observed in the Flinders Ranges in South Australia, remnants of the ancient glaciation. A geological field trip to the Ranges, led by Professor Alan Collins from the University of Adelaide, prompted the team to utilize the University of Sydney EarthByte computer models for a comprehensive investigation.
Connecting plate tectonic models with CO2 degassing calculations from underwater volcanoes along mid-ocean ridges, the researchers identified a crucial correlation. The onset of the Sturtian ice age aligned precisely with an unprecedented low in volcanic CO2 emissions. Moreover, the outflux of CO2 remained remarkably low throughout the entire 57-million-year duration of the ice age. During this period, Earth lacked multicellular animals or land plants, with atmospheric CO2 concentration predominantly influenced by volcanic outgassing and silicate rock weathering processes.
The study suggests a “double whammy” as the trigger for the Sturtian ice age. A plate tectonic reorganization minimized volcanic degassing, while simultaneously, a continental volcanic province in Canada began eroding away, absorbing atmospheric CO2. This resulted in a significant drop in atmospheric CO2 to levels below 200 parts per million, less than half of today’s concentration, initiating the glaciation.
The research prompts intriguing questions about Earth’s long-term climate future. Contrary to a recent theory proposing the evolution towards a supercontinent, Pangea Ultima, characterized by extreme heat, the Earth is currently experiencing a trend of lower volcanic CO2 emissions due to increased continental collisions and slowed plate movements. This raises the possibility that Pangea Ultima may experience a return to icy conditions.
Conclusion
The Australian geologists’ study not only unravels the mysteries of Earth’s ancient ice age but also offers valuable insights into the intricate interplay of geological processes and climate regulation. The research underscores the gradual nature of geological climate change, contrasting with the rapid pace of human-induced climate change. As we contemplate Earth’s past, these findings prompt us to consider the potential impacts of current human activities on the planet’s future climate.
