One of Japan's most active volcanoes could be close to a major eruption threatening the "Naples of the Eastern World", research suggests.
A team of experts developed pioneering techniques to map the natural "plumbing system" of Sakurajima volcano, on the south-west tip of the country, to discover a substantial growing magma reserve.
The magma build-up could see the volcano repeat its deadly eruption of 1914, which killed 58 people and caused widespread flooding in the nearby city of Kagoshima - dubbed the "Naples of the Eastern World".
The team believe the ground-breaking study could help improve eruption forecasting and hazard assessment at volcanoes across the world, providing an enhanced early-warning system for potential eruptions.
Dr James Hickey, from the University of Exeter's Camborne School of Mines, said: "What we have discovered is not just how the magma flows into the reservoir, but just how great the reservoir is becoming.
The international team of scientists focused their study around Aira caldera - a large, submerged crater caused by the violent explosion and subsequent collapse of a voluminous magma reservoir.
This vast crater acts as a magma storage zone that feeds the nearby Sakurajima volcano, one of the island's most active volcanoes with small, localised eruptions occurring nearly every day.
By combining recent GPS deformation measurements with other geophysical data and advanced 3D computer models, the team were able to reconstruct the magma plumbing system beneath the caldera.
The study showed that the volcano is being supplied with around 14 million cubic metres of magma each year.
The team believe that excessive build-up of magma may indicate there is growing potential for a larger eruption.
"From our data we think it would take around 130 years for the volcano to store the same amount of magma for another eruption of a similar size [to 1914] - meaning we are around 25 years away," Dr Hickey said.
