Volcanic Islands

'The Bismark Arc', is home to many volcanic islands that are subject to numerous scientific researches. The diverse types of rocks, volcanic history and erosional processes make this volcanic arc a hot discussion topic. 'Long Island' is part of the 'Vitiaz Straight' located 55km north of Papua New Guinea, it is positioned within the Bismark volcanic arc and will be a major focus of this report. Long Island is a complex volcano, "Such structures are mixed landforms. In most cases, they occur because of changes either in eruptive habit or in location of the principal vent area. A stratovolcano may form a large explosion crater that later becomes filled by a lava dome, or several new cones and craters may develop on a caldera's rim"(Brittanica Online).This report will be in reference with a combined more detailed report, describing in greater quantity , the types and chemistry of specific rocks, profile of the basin, and erosional processes.

Growth of 'Long Island' from ocean floor

Plate tectonics play a major role in how the islands within the chain have grown from the sea floor, and become what is seen today. Ritter Island and the entire island chain lays on top of the 'Philippine Plate' in which is moving easterly sub ducting underneath the 'Eurasian Plate'. The 'Pacific Plate' located to the west, is also sub ducting, under the 'Philippine Plate'(B. Taylor, 1979) There numerous theories to the development of the Bismark Seas volcanic arc all associated with plate tectonics

The Boundary of the Bismark Sea and the Pacific Ocean is in the region of four major segments: two transform faults, a spreading segment and most importantly one "leaky transform". Leaky transform faults are fracture zones created when a component of opening motion occurs across transform fault. As a result of this, the sea floor is continually spreading. Long Island is part of the 'Vitiaz Straight' located 55km north of Papua New Guinea, and is subject to

Volcanic arcs are located parallel to deep sea trenches as a result of two oceanic plate boundaries forming a subduction zone. Like continental subduction upwelling, magma slowly collects into diapirs (an intrusion that has forced its way into overlying rock), which slowly rises through the overlying crust towards the surface. Long Island is part of the 'Vitiaz Straight' within the 'Bismark Volcanic Arc' located 55km north of Papua New Guinea, and is subject to subdution. The subducting oceanic crust results in 'flux melting'. I.e. the melting of ultramafic mantle rocks to produce mafic magma (W.B Thorten, 2001), hence identified in the first four dredge samples ( MU10334, MU10346, MU10340 and possibly in MU10343). The magma produced from subduction zone uprising , slowly builds up on the oceanic surface, before eventually breaking surface of the water.( W.B Thorten, 2001) Long Island is just one examples of volcanic islands produced as a result of subduction mantle up dwelling. The base of the Long Island is approximate 60-70km and eruptions have been frequent over the last 20 years. For specific chemistry of rock types sea part four or group reports.

Geological make up of 'Long Island'

The makeup of the island is going to be a type of Volcanic Arc basalt (Tholeiite, Calc-alkali basalts, and Shoshonites). 15 samples where gathered by the process of dredging from four different locations, and has resulted in 10 rocks with volcanic properties, and 5 without. An Extremely powerful eruption left an enormous 86km2 Caldera crator on the Long island, referred to as 'Lake Wisdom'. There is very little evidence of lava flows within the caldera