Lost Sheep

Some heavily edited to suit my biased propaganda articles from Science Daily.

Your tastes may vary. …

Lost Sheep:

1. Indonesia's Puzzling Banda Arc: New Findings Explain Mystery Behind Geological Development.

ScienceDaily (July 27, 2010) — The Banda arc — a gigantic 1,000km long, 180-degree curve in eastern Indonesia — has puzzled geologists for many years.

The centre of three tectonic plates it comprises young oceanic crust enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian continental margin. A complex with the largest fold on Earth, with a depth of 650km, in a subducted plate.

The number of slabs being subducted has not even been agreed.
Two "schools" offering one- or two-slab interpretations with problematical models of evolution.

Robert Hall, Royal Holloway, and Wim Spakman, Utrecht University say:
Detailed reconstructions of tectonic evolution and seismic tomography shows the rollback of a single oceanic slab, rapid plate convergence and movement of the India-Australia plate northwards that caused the 2004 tsunami which devastated areas around the Indian Ocean.

The rollback at high speed is possible in such a convergent setting.

They also discovered that there was more subducted slab in the mantle than predicted now acting as an obstacle to the Australian plate moving north and therefore it has become deformed into a fold in the mantle down to 600km depth which is gradually getting tighter and tighter, with the two limbs of the fold getting steeper and closer together.

This is causing the crust to deform.

This deformation has contributed to the rapid elevation of the islands in the Banda arc, the largest of which are Seram and Timor, both of which have emerged from several kilometres below sea level to their present elevations — up to about 3 km above sea level — in the last couple of million years.

"These are remarkable vertical movements on geological time scales," explains Professor Hall. "In the Banda region we are seeing a mountain belt forming before our eyes — in geological terms — which is why it is so interesting to us. Some of the features we observe there will help us to understand older mountain belts. Professor Spakman's seismic tomography work, an area of study in which he has been a pioneer, has provided critical evidence and has enabled us to propose some new ideas that we think help explain much of what previously was not understood."

The researchers' solution to this longstanding geodynamic problem provides a new basis for understanding the past and present geology and geophysics of the region. Importantly, their findings show that the Banda arc subduction is not the result of a unique tectonic setting but has many past and present analogues around the globe, particularly in regions with (partially) land-locked oceanic basins, such as the Alpine-Mediterranean region, and Central America.


Let me try an analogy on you:

Why do three cars parked side by side in a massive d#car park over a period of millions of years crash into each other?

Because one of them is really an out of control Australian road train and the driver has fallen asleep at the wheel.

Doen't that suddenly make sense to you now of all the above?


One thought on “Lost Sheep

  1. The article mention two schools of thought but only discussed one of them. Or I missed the bit where they diverged.Maybe it got subducted?

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