This map from the University of California, San Diego, shows both height above sea level and depth below sea level. The height above sea level is a direct measurement from NASA altimetry data. The water depth below sea level is a combination of ship soundings and NASA altimetry measurements of the sea surface, which is affected by gravity and can be converted to the relative depth of the sea bottom. These two measurements can then be combined to give a continuous image of water depth below sea level as shown in the resultant map.
The NASA altimetry map shows the deepest part of the worlds oceans along the Mariana Trench, where the Pacific Plate is subducted under the Phillipine Islands and reachs a depth of 11,000 metres below sea level.
The continuing collision of the Australian Continent which includes Papua New Guinea, with the Pacific Plate has caused the thrusting and uplift of the east-west mountain range formed across Papua New Guinea. The NASA altimetry map includes Mount Puncak Jaya or Carstensz Pyramid which at 4884 metres above sea level is the highest mountain in Australasia.
The collision caused by the continuing northward movement of the Australian Continent and the continuing westward movement of the Pacific Plate has caused the westward curvature of the Indonesian Island Arc and the slicing off of large segments of the northern part of the Australian Continent (Papua New Guinea) and inserting them into the Indonesian Island Arc system.
One does not have to be a geologist to observe the westward curvature of the Indonesian Island Arc and the obvious large transform fault which has moved part of Papua New Guinea 500 kilometres to the west to collide with the central part of the Indonesian island of Sulawesi, which has been offset a similar distance from the northern part of the island.
These segments of the Australian Continent brought with them characteristic Australian fauna such as marsupials and birds to Eastern Indonesia. When the British naturalist Alfred Russel Wallace crossed from the island of Bali to Lombok in 1856 he observed the difference in the bird life:
During the few days which I stayed on the north coast of Bali, on my way to Lombok I saw several birds highly characteristic of Javanese ornithology … On crossing over to Lombok, seperated by a strait less than twenty miles wide, I naturally expected to meet with some of these birds again; but during a stay of three months I never saw one of them, but found a totally different set of species, most of which were entirely unknown not only in Java, but also in Borneo, Sumatra and Malacca. For example, among the commonest birds in Lombok were white cockatoos and honeysuckers, belonging to family groups which are entirely absent from the western region of the Archipelago.
Wallace had crossed the division between the fauna of Asia and Australasia which has since been named the Wallace Line in his honour. The altimetry map shows that this is the edge of the Asian Continent. On the Asian side of the Wallace Line are the Asian elephant, the rare Javanese rhinocerus, Sumatran tigers, Borneo leopards, the orangutans of Sumatra and Borneo and numerous birds specific to Asia. On the Australasian side are white cockatoos, the megapodes such as brush turkeys or maleo, the spectacular birds of paradise and marsupials such as the possum like cuscus.
Consequently Alfred Russel Wallace was one of the founders of the science of biogeography, also fifty years before the theory of continental drift and one hundred years before the science of plate tectonics he recognised that Australia had collided with Asia and along with Charles Darwin he was the co-discoverer of the origin of species. Not bad for someone who had left school at fourteen and was self educated in the libraries and Mechanics Institutes of Victorian England.
Read his story in ‘Where Australia Collides with Asia – The Epic Voyages of Joseph Banks, Charles Darwin, Alfred Russel Wallace and the Origin of On The Origin of Species’, and for more information please go to: