Mountain growth spurts may have sparked complex life on Earth

Mountain ranges grew higher throughout Earth’s history in two distinct “spurts” that correlated with the flourishing of biological diversity on our planet, according to new research published in the journal Science Advances. The study suggests mountains may have played a key role in sparking complex life.

‟Changes that occurred deep in the Earth ultimately gave rise to much taller mountains over time, which may have made our planet habitable by providing the nutrients needed for life to form and flourish,” said Dr. Matthijs Smit of UBC’s Department of Earth, Ocean and Atmospheric Sciences and lead author of the study. “Nutrients such as phosphorous are essential ingredients for life on our planet, but prior to three billion years ago, these elements were locked in the Earth’s crust and the oceans were quite nutrient-starved. All this changed when tall mountains started to develop.”

The researchers studied metamorphic rocks that were pushed deep underground by the pressure of tectonic plates over the past three billion years. Their results show that mountains developing where plates collided were able to become much higher over time. The growth spurts of the crust in mountainous regions drastically altered weathering and erosion patterns, providing nutrients to the biosphere and so enabling photosynthesis to help raise atmospheric oxygen levels. By the time of the first global oxidation event 2.2 billion years ago, mountains had grown from near sea-level to about half as high as today’s Himalayas. The second growth spurt came at the time of the second major oxidation event around 700 million years ago.

‟The first growth spurt may have led to the emergence of land on a large scale for the first time, while the second growth spurt thrust mountain ranges to enormous heights,” said co-author Dr. Douwe van Hinsbergen of Utrecht University, The Netherlands. ‟Given such profound effects, mountains may well have played a far greater role in the creation of a habitable planet than previously assumed.”

Around the time of these two growth spurts, the maximum thickness that the crust in mountain belts was able to achieve increased dramatically—first 30 to 60 km and later to almost 90 km. ‟We suspect that these increases are ultimately linked to the cooling of our planet,” Dr. Smit said. ‟As a result, the process that makes mountains changed, allowing mountains to grow taller.”

Mountains have come and gone throughout Earth’s history, but few have ever reached the heights we see today. The three highest peaks on Earth—Mount Everest, K2 and Kangchenjunga of the relatively young Great Himalaya—stand almost nine kilometres above sea level and rest on a crust up to 80 kilometres thick, which is about double the thickness of most other continents. The leaps that mountains have made over time likely represented massive and irreversible increases to the amount of matter weathered in to the oceans.

‟It’s likely not a coincidence that life on Earth developed and diversified approximately during the same period that the two growth spurts occurred,” said co-author Dr. Ellen Kooijman of the Swedish Museum of Natural History, Stockholm. ‟It’s exciting to think that mountain belts were once non-existent and that their development over the past three billion years may have driven the environmental and biological change that shaped our planet.”