Until now the monstrous Banda Detachment fault line in eastern Indonesia has remained a mystery.
But geologists exploring the 7km abyss under the Banda Sea have finally worked out how it was formed after documenting it for the first time.
Now the groundbreaking research into the fault may allow scientists to predict killer tsunamis in the region – potentially saving millions of lives.
The whopping fault is located in the so-called Ring of Fire, which surrounds the Pacific Ocean and is the site of approximately 90% of the world”s earthquakes.
Research from a team of scientists lead by Jonathan Pownall from The Australian National University (ANU) could prevent disasters in the future.
He said: “The abyss has been known for 90 years but until now no one has been able to explain how it got so deep.
“Our research found that a 7km-deep abyss beneath the Banda Sea off eastern Indonesia was formed by extension along what might be Earth”s largest identified exposed fault plane.”
By analysing high-resolution maps of the sea floor, the team found hundreds of scarred rocks – indicting the Earth’s crust had been ripped apart.
Dr Pownall said this tear in the ocean floor is 60,000 square km long.
Pownall added: “In a region of extreme tsunami risk, knowledge of major faults such as the Banda Detachment, which could make big earthquakes when they slip, is fundamental to being able to properly assess tectonic hazards.”
It comes amid fears millions of people could be wiped out by a long-forecast super earthquake dubbed “The Big One”.
The US west coast – including major cities in California, such as Los Angeles and San Francisco – is thought to be at “high risk” of a major tremor, which could kill millions.
Last week a massive 7.3 magnitude earthquake rocked Japan – triggering a tsunami off the east coast.