Vitiaz Arc

27 Jan 2018

A study in the Proceedings of the Royal Society B (January 2018) have been looking at lizards in Australasia, Melanesia and Polynesia. We are told that when you scroll back the distribution of geckos, and their variants, they have a common ancestor that may go back to the Vitiaz Arc, a near continuous chain of islands that stretched across the Western Pacific 30 to 40 million years ago (during the Oligocene). Nowadays, the arc is represented by landforms such as the Philippines and a string of islands as far as Fiji. At that time the land masses differed - and what leaps out is an 'inferred' long chain of islands stretching across the Pacific. One may also wonder how that chain also correlates with human migration - especially of Melanesians (as opposed to Polynesians who used boats to colonise the islands). This isnot say Melanesians did not use boats - but they were not in the same league as Polynesian boats that were ocean going. Today, the arc is severely fragmented - and islands have shifted, we are told. How that happens is unclear. The arc included the Philippines, Solomon Islands, Fiji, Vanuatu, and various other smaller islands. They were once closer we are told - which again is a strange thing to say. If the islands were bigger they would be closer - and visible from one part of the arc to the other. We may note a redistribution of the ocean waters may also have changed the configuration - but this is not of course mentioned. See ... DOI:10.1098/rspb.2017.1760 (the DOI link at Phys Org will take you to the abstract but the actual article is paywalled, which is a pity as a nice map of the Vitiaz Arc would have been nice. The Dorling Kindersley World Atlas appears to show New Guinea as part of the arc - and various trenches to the edge of the arc which together with volcanoes appears to mark a plate margin. The World Atlas of the Oceans (Firefly Books) shows something similar. There is an extraordinary amount of continental shelf off the coast of East Asia and various areas of lower sea levels between Japan and the Philippines - with others spanning out towards the Solomons (and that is without bringing in Zealandia).