Origins of the Banda Arc Explained

Scientists have been wondering where the massive Banda Arc originated from for decades. The immense, arc-like fold in our planet's crust is located at the intersection of some major tectonic plates, but until now no research team was able to explain the processes that led to its formation. The geological mystery has therefore remained a mystery until now. A team of experts believes it may have just discovered the reason why the Arc appeared in the first place, OurAmazingPlanet reports.

“We have used two independent methods: plate tectonic reconstructions based on geology observed at the surface, and structure of subducted lithosphere observed in the mantle based on seismic tomography, and we believe this enables us to offer a new solution to this enigma which resolves many of the problems,” says University of London expert Robert Hall. The Banda Arc, he adds, is located right atop the area where three major tectonic plates meet each other. The India-Australia, Eurasia and Pacific tectonic plates are some of the largest and most active in the world today.

The feature they apparently formed is a 180-degree arc, which is more than 1,000 kilometers (600 miles) long. Geographically, it stretches across eastern Indonesia, and is delimited by an active inner volcanic arc. The outer arc contains numerous islands, and its internal structure contains young oceanic crust exclusively. The reason why they are deformed in this manner is however a mystery. No other location on the planet features such as clear, naturally-produced geometric shape on the intersection of tectonic plates, geologists say.

The UL researcher, working together with expert Wim Spakman from the Utrecht University in the Netherlands, now proposes that the entire arc is nothing more than the result of a rapid rollback happening in an oceanic slab. Details of the new investigation were published in the July 25 issue of the esteemed scientific journal Nature Geoscience. The team also says that a large piece of planetary crust, already submerged in the planet's mantle, may also be contributing to the uplift.

“It is an interesting commentary that despite the fact that we can see most of the geology at the surface – although this is still a remote and difficult region for field geologists – it has still been difficult for Earth scientists to work out what has happened,” Hall concludes.