Some problems of volcanism in Iceland

摘要: Until two decades or so ago the petrography of Iceland seemed to present a rather simple picture. About 99 per cent rocks were regarded as basaltic, 1 rhyolitic and intermediate composition nearly non-existent. Recent research has changed this Central volcanoes producing acid lava tephra have played considerable role both in Tertiary Quaternary. Contrary massproducing basalt volcanoes, fed by deep-seated uniform magma source, differentiated central are normally separated chambers at smaller depth, where differentiation takes place between eruptions, resulting products which bridge “immiscibility gap” basalts rhyolites. Eight ten postglacial lavas tephras about 25 historical ones intermediate. Opinions still differ whether existence these can be explained solely result gravitational parent partly remelting continental layer beneath plateau-basalts. There are, however, some strong geological evidences favour such they seem moment not contradicted geophysical research. The Surtsey eruption demonstrated close relation craterrows, shieldvolcanoes tablemountains convincingly shown how greatly external circumstances may influence volcanic activity shape volcano. focused interest on neovolcanic zone supra marine part Mid-Atlantic rift-ridge zone, taken under similar conditions along its submarine parts, viz. water (glacial meltwater) when Pleistocene ice-sheets blanketed activity. Similar morphological types therefore expected cases, steepsided mounds long ridges.