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Volcanic activities frequently occur along plate boundaries where pressure underneath the crust is released through cracks – pushing out magma and sometimes water and steam. The process of volcanism denotes eruption of molten rocks at the earth’s surface, often accompanied by rock fragments and explosive gases. Volcanism can take various forms, one being the creation of new crust along some 50,000 kms of ocean floor fissures where molten rock penetrates the surface and begins its divergent movement at the mid oceanic spreading ridges. In fact about 75 per cent of the world’s volcanoes are on the seafloor.