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What
triggered a massive ice age on Earth 480 million years ago? Scientists
have a surprising answer: the humble moss.
The simple plants' interactions with rocks are believed to be the cause.
"The humble moss has created the climate which we enjoy today, from which the life we see all around us evolved," said Prof Tim Lenton of Exeter University, one of the lead researchers.
Carbon dioxide insulates the planet, rather like a duvet wrapped around it: the higher the concentration of CO2, the higher the average global temperature.
Atmospheric levels of the gas 480 million years ago are thought to have been 16 times higher than they are now, and average global temperatures are thought to have been 25C, around 10C higher than they are now.
But by 460 million years ago, CO2 levels had fallen by half and the planet began to cool, allowing the formation of the polar ice caps.
The question is: what caused the drop in CO2 levels? The answer, according to an experiment by Prof Lenton and his colleague Prof Liam Dolan of Oxford University is "moss".
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Scientists have long pondered an event 12,900 years ago that caused the disappearance of the Clovis people of North America and the extinction of large mammals such as the mammoth, mastodon, saber-toothed cat, and the North American camel. One theory is that a comet broke into fragments and showered burning material over the continent. Now there’s some evidence -a layer of nanodiamonds have been found at a layer of sediment buried 12,900 years ago. The diamonds could have only been formed by a high-pressure high-temperature event.
These diamonds are measured in nanometers — mere billionths of meters — and one of them would not suffice for an engagement ring unless the recipient had an extremely small finger. Indeed, these diamonds are visible only with the aid of the most advanced microscopes.
The wide distribution of the nanodiamonds could be a sign that the comet broke into pieces in space and that the fragments burned up explosively over a broad area of North America. The heat and pressure from the event transformed carbon on the planet’s surface into the tiny diamonds, the scientists said.
“Imagine these fireballs exploding in the air. A Clovis hunter standing and looking at these things would have seen a canopy of fire as these things came in and exploded,” said Allen West, a geophysicist and one of the paper’s co-authors. “There would have been no sound. There would have been massive explosions. Brilliant light, brighter than the sun. There would have been radiant heat — it would have been capable, at the very least, of giving him serious burns and, at the maximum, of incinerating him.”
This theory would explain the climate change at the time, when the warming planet was plunged into another, shorter ice age. Skeptics cite lack of a crater or other surface evidence in refuting the theory. Link -via Digg
