String of peaks

A mammoth ring of mountains could have once stretched from Spain to New Zealand

 
Published: Saturday 04 July 2015

 Mighty mountains: the Himalay the Alps, the Himalaya and the Caucasus mountains once formed part of an unbroken chain of a mountain range some 40 to 45 million years ago. According to two Australian geologists, this colossal mountain range stretched all the way from Spain, through Asia, to the southwest Pacific, may be as far as New Zealand ( New Scientist , Vol 153, No 2075).

The new theory is based on evidence provided by rocks found in Europe and the Pacific. The rocks reveal clues about the missing mountains in the 15,000-kilometre chain. Many of these mountain ranges came into existence when three parts of the supercontinent Gondwanaland -- Africa, India and Australia -- collided with a supercontinent in the north. During the same period, the Indo-Australian plate was moving towards north-east and slipped under the landmass of Eurasia in a process called subduction. Parts of the earth's crust were pushed down to a depth of about 70 kilometres. These crusts form into rocks called blueschists and eclogites at this depth, where the pressure is 15 to 20 kilobars and temperatures reach around 500 c .

Gordon Lister, director of the Australian Crustal Research Centre at Monash University in Melbourne, and his student Tim Rawling had found these rocks at the surface of several Greek islands, in New Guinea and on the island of New Caledonia, east of Australia. They say that these are the remains of the mountain chain which formed along the boundaries of the colliding plates. Lister and Rawling believe that the Indo-Australian plate broke at its 'hinge' and most of the giant mountain range disintegrated and later formed the blueschists and eclogites.

Lister said his idea may be controversial but he hopes to strengthen his theory by other records of migration of plants and animals which may add further evidence to the debate.

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