Volcanologists might need to update their ideas about how molten rock travels from deep within Earth to erupt at the surface.

Magma needed just a week and a half to rise from more than 20 kilometres below Earth’s surface to erupt as lava from a now-dormant Icelandic volcano, scientists estimate. The finding could prompt volcanologists to revise their methods of predicting future eruptions.

Euan Mutch, John Maclennan and their colleagues at the University of Cambridge, UK, studied lava flows from the Borgarhraun eruption, which took place in northern Iceland between 7,000 and 10,500 years ago. The chemistry of crystals in the lava indicated their depth in Earth’s crust when the magma began moving upwards and how the magma cooled as it rose.

The magma zipped from 24 kilometres deep to the surface in about 10 days — the fastest ascent ever recorded for one of the planet’s most common types of molten rock. It rose so quickly that there was no time to release much of the carbon dioxide trapped within it.

This suggests that the common strategy of monitoring the carbon dioxide emissions of active volcanoes might in some cases provide only a day’s warning of an imminent eruption.