WELLINGTON, Sept. 6 (Xinhua) — New Zealand scientists said Tuesday that they had unlocked the secret to better predicting devastating volcanic eruptions that account for 50 percent of volcanic deaths and endanger half a billion people worldwide.

Massey University researchers claimed to have made the first observations of the internal structure of volcanic flows known as pyroclastic density currents or pyroclastic flows.

The exact cause of pyroclastic flows, which send avalanches of fast-moving clouds of hot ash, rock and gas down the flanks of volcanoes, has long been the subject of speculation.

The ancient Roman city of Pompeii was just one example in a long line of lethal incidents involving these flows, which researcher Dr Gert Lube described as "amongst the most destructive phenomena on Earth."

"Pyroclastic flows are the most common and lethal volcanic threat, and by analyzing the internal structure we are laying the foundations to understand how they will behave in an eruption," Lube said in a statement.

The study sought to create a view inside the flows to define how two currents - the non-turbulent underflow and fully turbulent ash cloud-regions - were able to harmonize and control the severity of the flow itself.

However, measuring the inside of an avalanche of several tonnes of rock, gas and ash had proven impossible because of the heat and destructive force of the flows.

The researchers used Massey's unique eruption simulator to synthesize the natural behavior of the flows in unique large-scale experiments.

The simulator worked by dropping ash and pumice down a narrow channel while high-speed cameras and sensors capture the data.

The results indicated that the currents met in a previously unrecognized turbulent middle zone, meaning there were not two currents, but three.

"Inside this middle zone, the gas-particle mixture behaved fundamentally different from the turbulent suspension cloud above and the particle-rich avalanche of pumice below," said Lube.

The volcanic particles spontaneously associated in a pattern of dendritic or branch-like particle clusters called mesoscale clusters.