Magma Under Pressure Stores Extra Oxygen, Study Finds

Researchers at HPSTAR found that molten basalt at pressures up to 7 GPa holds more than 5% excess oxygen by weight beyond conventional accounting. As magma rises and pressure drops, that oxygen could be released, possibly contributing to atmospheric oxygen increases 2.5–2.0 billion years ago.

• At 7 GPa excess oxygen exceeded 5% of sample weight; controls gave 0.2–0.5%
• Experiments ran at 1,200–1,800 °C and pressures from 1 atm to 7 GPa
• Releasing just 0.27% of erupted magma mass as oxygen matches today's atmosphere
• Raman spectroscopy found no O₂ gas, indicating oxygen entered the glass structure