The terrestrial mountains? They exist thanks to marine microorganisms
"The additional carbon allowed for easier deformation of the crust, in a way that built the mountain belts, and therefore the plate edges characteristic of modern a plaques, "the researchers write.
The changes appear to have started about 2 billion years ago, in the middle of the paleoproterozoic era, when the biological carbon of plankton and bacteria began to add exceptionally high concentrations of graphite to the shale of the ocean floor. This made the rock brittle and more easily stackable.
Within 100 million years, most mountain ranges started forming in these weakened slices of crust. The more recently emerged mountain ranges follow the same pattern. In the Himalayas, for example, the tectonic thrust about 50 million years ago focused on paleoproterozoic sediments with the richest organic matter beds.
"Ultimately, what our research proved that the key to the formation of mountains was life, showing that the Earth and its biosphere are intimately connected in ways not previously understood, ”explains geologist John Parnell of the University of Aberdeen in Scotland. In the past, numerous studies have shown that tectonic plates must be weakened by graphite to create mountains, but how this is done is less clear.
New research suggests marine life is a key part of the process. All 20 mountain ranges studied revealed a high concentration of black shale together with graphite, which appears to come from a biological origin. The surge in marine life 2 billion years ago most likely occurred in response to the Great Oxidation Event, when photosynthesizing bacteria began producing large amounts of oxidizing substances, capable of supporting new single-celled life forms, such as an abundance of marine plankton.
Yet mountain formation doesn't require much biological carbon either. Only a small percentage of biomass is required for the edges of the tectonic plates to slide over each other when they collide. In mountain ranges made up of paleoproterozoic sediments, however, the carbon content is consistently above 10%. Scientists have found that it sometimes reaches as high as 20%.
In short, it appears that a dramatic surge in marine life billions of years ago set the stage for many of the mountain ranges we see today. If the team is right, it means that microscopic single-celled organisms, which float invisibly in the sea, may have played a key role in the creation of some of the largest geological structures on our planet.
