An unprecedented abundance of oceanic life played a crucial role in the creation of Earth’s first big mountains, a study led by scientists at the University of Aberdeen and published in the journal Communications Earth and Environment has revealed.
“Mountains are an essential part of the landscape, but big mountain chains only formed half-way through Earth’s history, about two billion years ago,” explains author Professor John Parnell from the University’s School of Geosciences.
While the formation of mountains is usually associated with the collision of tectonic plates causing huge slabs of rock to be thrust skywards, the study has shown that this was triggered by an abundance of nutrients in the oceans two billion years ago which caused an explosion in microscopic life.
The motion of tectonic plates likely began about 3.5 billion years ago, driven by mantle plumes pushing aside parts of the Earth’s crust. But to allow the tectonic plates to move and solid masses of rocks to slide over each other, a lubricating material is needed.
Graphite, a carbon mineral, can act as auch a material. Graphite and graphite powder are valued in industrial applications for their self-lubricating and dry lubricating properties.
Life on Earth appeared about 3.5 billion years ago and is mostly carbon-based.
When the microorganism populating Earth’s early oceans died, they fell to the ocean floor, eventually forming graphite which played a crucial role in lubricating the breakage of rocks into slabs, enabling them to stack on top of each other to make mountains. The study has revealed that the amount of planktonic life was unusually high about two billion years ago, thus creating the necessary conditions that were crucial to the emergence of mountains over millions of years.
“The geological record for this period includes evidence of an abundance of organic matter in the oceans, which when they died were preserved as graphite in shale. While it has long been known that tectonic processes were lubricated, our research shows that it was the sheer abundance of carbon in the ocean that played a crucial role in the crustal thickening that built the Earth’s mountain ranges. We can see the evidence in the northwest of Scotland, where the roots of the ancient mountains and the slippery graphite that helped build them can still be found, in places like Harris, Tiree and Gairloch,” Professor Parnell explains.
“Ultimately what our research has shown is that the key to the formation of mountains was life, demonstrating that the Earth and its biosphere are intimately linked in ways not previously understood.”
Study co-author Dr. Connor Brolly, from the University of Glasgow, said: “Graphite buried in Earth’s crust is in high demand for future green technology, for use in items such as fuel cells and lithium-ion batteries. It’s interesting to think that this two-billion-year-old event which was responsible for shaping our natural world now has the potential to play a key role in its preservation for future generations.”