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Show Volcanic Forces of Pressure and Steam Originate Deep in the Earth In most cases the mighty forces that start and continue volcanic eruption the squeezing force of gravity and the explosive forces of steam and other gases originate deep in the earth, probably many miles down. The melted rock or lava that is an essential part of most eruptions, also starts from these great depths. It is pushed up the pipe of the volcano to the crater, where it flows out or is exploded out. When an eruption has run its course, the lava in the pipe cools and solidifies. If it completely seals up the pipe with a plug of rock, the volcano becomes dormant or extinct. ex-tinct. If the pipe is choked down to very small proportions, so that a trickle of lava and hot gases rise to keep a little cauldron of molten rock bubbling in the crater, the Tolcano remains slightly active. All the bombs in existence dropped on the top of the cold, solid plug of a dormant volcano could not wake the sleeping forces far below. In the case of a slightly active vol--cano, even the explosion of the biggest big-gest bombs would do little more than splash lava about the crater. Bombs have been used advantageously advan-tageously in controlling one kind of volcanic phenomena. On the slopes of Mauna Loa on the island of Hawaii, Ha-waii, lava streams that threatened to flow into villages and even into the city of Hilo, have been turned aside by bomb explosion. |