MASSIVE volcanic eruptions throughout Earth’s history have released huge amounts of carbon dioxide into the air. But geologists have had trouble figuring out where the carbon comes from. The Earth’s mantle has long been thought to hoard carbon inside crystals of olivine, but little of this mineral turns up in magma.
Now Hans Keppler from the University of Tübingen in Germany and colleagues have found that olivine is not a carbon storehouse after all. They tried to squeeze carbon into olivine crystals at temperatures and pressures similar to those found 120 kilometres underground, and found the rocks would only hold…
