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Shortly before the eruption, a giant boil of a mountain grew above the increasing quantities of molten material below. When the solid groound finally gave way, a searingly hot plume of ash was thrown into the sky-its remains can be traced today over an area of 20-30.000 sq km. Around the volcano the ash settled in a layer more than 600 m thick. This eruption set the world record for the quantity of material ejected-some 1.500-2.000 cubic km, compared with just 0,6 cubic km for the much-publicised eruption of Mt. St. Helens in Washington State, USA. Because of the massive quantity of ejecta, the empty cone soon collapsed in on itself to form the world's largest caldera. This became an ancient lake, which was itself destroyed about 30.000 years ago when a second, much smaller eruption occured. The island of Samosir in the center of the lake, and the lake's eastern shore-the main tourist centers today-are all that remain of the shattered cone.
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