Boisa volcanBoisa volcano forms a tiny island offshore from Bogia on the Madang coast. There are no known historical eruptions from Boisa volcano.
It is located only 10 km NW of Manam volcano, and it is a possible that Boisa belongs to the same volcanic edifice and is supplied by the same magma chamber,- in other words, really is a side vent of Manam rather than a separate volcano.
Introduction:From Smithsonian / GVP volcano information:
The small, 1.4 x 1.7 km Boisa, or Aris Island consists of a large basaltic-andesitic cone with a summit crater open to the north whose rim extends to the island's east coast. The crater of the basaltic older cone is filled by two steep-sided andesitic lava domes, the highest of which forms the 240-m high point of the island. A third lava dome, separated from the eastern cone by a low saddle, forms a peninsula on the western side of the island. No historical eruptions or present-day thermal activity have been observed, although the last eruption may have been quite recent judging by the youthful morphology of the island (Gust and Johnson, 1981).
Gust D A, Johnson R W, 1981. Amphibole-bearing inclusions from Boisa Island, Papua New Guinea: evaluation of the role of fractional crystallization in an andesitic volcano. J Geol, 89: 219-232
Cliquez ici pour recommander cette page à un ami