Tungurahua volcano
An eruption at the Tungurahua volcano in Ecuador in 2010.Reuters

A team of researchers have developed a technique for working out how much magma is stored beneath Earth's surface – a mystery which has long baffled scientists.

Published in the journal Nature, a team from the University of Geneva say they have discovered a technique to estimate the volume and flow of molten rock required for the construction of magma chambers – large underground pools of liquid rock that cause volcanic eruptions when placed under too much pressure.

How much magma is underground is difficult to establish because it normally cools and solidifies several kilometres beneath the planet's surface. It is only exposed after millions of years of erosion.

Three experts - a modelling specialist, an expert in the mineral zircon and a volcanologist - worked together to come up with a new technique that will allow better predictions of volcanic eruptions, as well as identify areas rich in natural resources related to magma.

They proposed a model that will determine the age, volume and injection rate of magma that has accumulated deep underground.

Zircon specialist Urs Schaltegger said: "The zircon crystals that are found in solidified magma hold key information about the injection of molten rock into a magma chamber before it freezes underground."

By looking at data from natural samples and numerical simulations, the team came up with a model to establish that the age of crystallised zircon in a cooled magma reservoir depends on the flow rate of injected magma, as well as the size of the reservoir.

Volcanologist Luca Caricchi said: "When we determine the age of a family of zircons from a small sample of solidified magmatic rock, using results from the mathematical model we have developed, we can tell what the size of the entire magma chamber was, as well as how fast the magma reservoir grew.

"This information means that we can determine the probability of an explosive volcanic eruption of a certain size to occur. In addition ... we will be able to identify new areas of our planet that are home to large amounts of natural resources, such as copper and gold."