The Puncak Jaya Papua New Guinea, the second largest island in the world, has been assembled by mass

The Puncak Jaya Papua New Guinea, the second largest island in the world, has been assembled by massive tectonic collisions over the past ~25 million years. One of the more remarkable results of these collisions is the Puncak Jaya, the highest island peak in the world. The southern portion of Papua New Guinea is part of the Australian continental craton. The rocks are Precambrian, likely well over a billion years old. 25 million years ago, there was a piece of oceanic crust off the north coast of Australia. That ocean was being subducted, similar to the scenario occurring further to the west off the coast of Java and Sumatra today. But, that subduction zone ran into a wall. Australia kept trying to push north, but it ran into other rocks, most likely parts of island arc chains. Eventually, the only thing the rocks could do was go upwards. The rocks of Puncak Jaya are limestones. They were formed tens of millions of years ago at the bottom of a shallow ocean. Since then, they’ve been thrust upwards over 4800 meters. This area has proven to be extremely climate-sensitive. You see some actual glaciers in this image; the glaciers in this area are retreating rapidly. Decades ago, on the main peaks, there would have been glaciers visible; today many of the largest glaciers in this area have completely disappeared, and the remaining ice was reportedly retreating by meters per year and may not last the decade. -JBB Image credit: Papuaweb.orghttp://www.papuaweb.org/main/wallpapers/muller-glacier-1280-960.jpg Resources:http://www.easternsnow.org/proceedings/2004/kincaid_and_klein.pdf#search=%27meren%20glacier%27http://www.oppb.org/history-west-papua/geology-process/http://gsabulletin.gsapubs.org/content/108/11/1438http://aapgbull.geoscienceworld.org/content/89/1/119.abstract -- source link

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