Mountain made: An artist's illustration of what the Ediacaran fauna may have looked like. These strange, soft-bodied animals were a kind of abortive early attempt at complex life.
Credit: Joshua Sherurcij / Wikimedia
SYDNEY: Oxygen that allowed complex organisms to first flourish, hundreds of millions of years ago, came from the 'extreme erosion' of Earth's largest ever mountain range, geologists have found.
The mountain range, was 8,000 km long and spanned the ancient supercontinent of Gondwanaland around 600 million years ago.
The mountains coincided with the time when life evolved from simple, single-celled organisms, into a myriad of bizarre, soft-bodied animals. These strange creatures, known as the Ediacaran fauna, first appeared 575 million years ago, and included some animals up to two metres long.
"Extreme erosion"
Now experts have found evidence that this early evolutionary explosion came about because of rapid erosion led to a massive influx of nutrients into the ancient oceans.
Australian volcanologist Rick Squire will present the finding on Thursday at the Selwyn Symposium, a conference on Earth's early life, to be held at the University of Melbourne.
"Prior to about 580 million years ago there were only single-celled organisms floating around the sea. Suddenly something really radical happened and [life] switched to big complex organisms," Squire told Cosmos Online. "It was the most extreme erosion event in the Earth's history."
While other theories have pointed to continental erosion as the impetus for the Ediacaran evolutionary explosion, this is the first to pinpoint a particular mountain range as the driver for the evolution of complex animal life.
Three times longer than the Himalayas
The 'Transgondwanan Supermountains' would have been three times longer than the Himalayas. Forced upwards by the collisions of continents that later separated into Africa, India, Arabia and Antarctica, the mountains were located in the monsoon belt where erosion is most intense.
As they formed between 635 and 515 million years ago, they would have been worn down by the action of wind and rain, said Squire, who is based at Monash University in Melbourne. This provided a huge flux of the nutrients that are essential for complex life, and also triggered the dramatic increase in oceanic oxygen concentrations that were crucial for animals to flourish, he said.
The excess nutrients washed off the mountains would have led to the rise of massive algal blooms, said Squire, which were then rapidly buried in sediments. Dead algae are normally decayed by bacteria which consume oxygen in the process, locking it away.
However, Squire suspects that, because the algae were buried very rapidly, the bacteria didn’t get a chance to process them, and the oxygen remained in the upper levels of the ocean. Over time, the oxygen levels built up, permanently altering the composition of the atmosphere.
Oxygen levels jumped from five to ten per cent of today's level to around up to 60 to 80 per cent by the time the mountain range was fully formed, said Squire. 'That was the biggest increase in oxygen concentrations in the Earth's history.'
