NEW GUINEA, island, of estimated area 312,329 sq.m., stretching from the equator in the north-west to 12° 5' S. in the south-east and from 13o° 50' E. to 151° 3o' E. ; sepa rated from Australia by the shallow Torres strait and Arafura sea. On its eastern side lies the Bismarck archipelago.
The island consists of a long central mountain chain of complex formation, a northern coastal range, and a small planed down hill country on the south coast, west of the mouth of the Fly river, together with the alluvial surfaces formed mainly by the rivers under the influence of equatorial rains. The structure shows, in the west, the influences of great earth movements ranging from the Banda sea. These give arcs (I) Banda islands, (2) Buru, Ce ram, West Timorlaut, (3) East Timorlaut, Kei islands, coastal mountains of south-west New Guinea from the Baik mountains to Cape Fatingar, thence via Misol island, Obi island, and then north on the west side of Halmahera. This curve is separated, in West New Guinea, from the central chain by the deep McCluer inlet. The central chain stretches from north-west to south-east. In the west the ranges of the central chain are called Charles Louis Mts. and then for a while, still in Dutch New Guinea, the name Nassau Mts. is used. Here the snow line is approximately at 14,600 ft. and Mt. Idenburg (15,15o ft.) and Mt. Carstens (16,40o ft.) have glaciers. The next section is the Orange Mts. with Mt. Wilhelmina (15,312 ft.). There seems to be a more or less parallel range 25-45 m. to the north of this succession of ranges, and in it a height of 12,500 ft. has been observed in the Weijland mountains. The composite nature of the great chain is maintained eastwards and it is believed that the main watershed lies in the Mandated and not in the British Territory. In the former a height of 13,700 ft. has been found in the Otto Mts. ; on the south flank the chain grades into a complex of mountains of lesser height. The south-eastern part of the chain called the Owen Stanley range (Mt. Albert Edward, 13,22o ft.) declines gradually to the end of the long peninsula.
Towards the west the central chain is formed principally of palaeozoic sandstones and slates on which much younger rocks, nummulitic sandstone and limestone are laid. In Dutch New Guinea, the lower mountain country is of Miocene rock. Towards the south-eastern peninsula there are again old rocks, some with gold-bearing quartz, especially along the axis, as well as granite and folded Tertiary limestone on both coasts of the peninsula; here also, and in the d'Entrecasteaux islands is much evidence of volcanic activity (Miocene, Pliocene, Pleistocene and recent).
. The northern coastal range in Dutch New Guinea is said to reach a height of about 6,90o ft.; it declines towards the mouth of the Sepik, beyond which it rises again to a height of about 10,500 f t. and ends at King William's cape. It is formed of an cient elements with diorites, gabbro, andesites, etc., mostly cov ered with Tertiary and even possibly younger sediments, and is probably still in process of uplift ; recent coral reefs adorn some cliff sides and may reach a level of some 5,500 feet. There is abundant evidence in New Guinea of large earth movements from Miocene times onwards, with a probable maximum in the Pliocene or Pleistocene. The southern hills between the mouths of Digul and Fly rivers are an extension of Australia structurally. Be tween these lines of hills there run lowlands, floored near the Iden burg river by Pliocene sandstones.
The most important rivers are the Mamberamo, reaching the sea north of the Nassau range; the Sepik, also on the north, navi gable by seagoing steamers for 18o m. ; the Fly river flowing into the Gulf of Papua, navigable by a whale boat for 600 miles; and the Digul in the south-west. Many of the rivers have gold, but it is important in few places save the Louisiade archipelago beyond the south-east extremity and Woodlark island. Murua (Woodlark island) beyond the d'Entrecasteaux islands has banded quartzite much valued by the people for the making of stone adzes. Pe troleum occurs near the coast of the Gulf of Papua.