Magma may carry hidden oxygen from deep inside Earth

In lab tests, molten basalt under high pressure took up extra oxygen, more than 5 per cent of its weight at 7 gigapascals.

As magma rises and pressure falls, it could release that oxygen. Researchers suggest this may help explain rises in atmospheric oxygen 2.5 to 2.0 billion years ago.

Oxygen released

0.27 % of magma weight

A rough estimate: if erupted magma released just 0.27 per cent of its weight as oxygen, it could have supplied as much as today's atmosphere holds.