Geology of the Rocky Mountains Japan, Indonesia and the Aleutians; others are fragments of oceanic crust obducted onto the continental margin while others represent small isolated mid-oceanic islands. Magma generated above the subducting slab rose into the North American continental crust about inland. Great arc-shaped volcanic mountain ranges, known as the Sierran Arc, grew as lava and ash spewed out of dozens of individual volcanoes. Beneath the surface, great masses of molten rock were injected and hardened in place. For 270 million years, the effects of plate collisions were focused very near the edge of the North American plate boundary, far to the west of
Journey to the Centre of the Earth (album) flee the forest for the Lidenbrook Sea and enter a dark tunnel that plunged deep into rock which they blast through with dynamite. The explosion causes an earthquake, and they become trapped in an active volcano shaft which projects them to the surface of the Earth by Mount Etna in Sicily. The concerts and album were first announced in October 1973, and organised during a break when Yes were touring "Tales from Topographic Oceans". Two sell-out performances were held at 6 and 8 p.m. on Friday 18 January 1974 at the Royal Festival Hall in London, attended by 3,000 people