The Earth’s ex­plo­sive skin con­di­tion...

More than half a bil­lion peo­ple through­out the world live near a vol­cano. Vol­ca­noes are usu­ally sur­rounded by fer­tile farm­land, and cheap en­ergy is of­ten easily avail­able. On the other hand, vol­ca­noes are tem­per­a­men­tal, and no­body knows ex­actly when the n

Science Illustrated - - CONTENTS -

Vol­ca­noes are Earth's nat­u­ral relief valves. When too much magma is un­der too much pres­sure close to Earth’s crust, a vol­cano de­vel­ops – or an ex­ist­ing one erupts one more time. There are vol­ca­noes on all con­ti­nents, in­clud­ing Antarc­tica but the ma­jor­ity of the vol­ca­noes in the world are lo­cated in places, where the tec­tonic plates meet. Their most fre­quent oc­cur­rence is the “Ring of Fire” in the basin of the Pa­cific Ocean.

The ex­act num­ber of vol­ca­noes is un­known, as it de­pends on how you de­fine a vol­cano – whether it must be ac­tive, and if all craters in ma­jor vol­canic ar­eas count as sep­a­rate vol­ca­noes. It is es­ti­mated that 1,300-1,500 vol­ca­noes ex­ist that have erupted over the past 10,000 years. More­over, there is a large quan­tity on the bot­tom of the oceans. Some vol­ca­noes are only a crack in the ground, while oth­ers develop over mil­lions of years, end­ing up as the South Amer­i­can Ojos del Sal­ado, which rises to an al­ti­tude of al­most 6.900 m, mak­ing it the world’s high­est vol­cano.

Just like sizes and shapes of vol­ca­noes, their tem­per is de­ter­mined by the type of magma which pow­ers them. Some magma flows easily out of the crater and down slightly in­clin­ing slopes. Other types are vis­cous, flow­ing with much more dif­fi­culty, pos­si­bly caus­ing "con­sti­pa­tion", i.e. al­most act­ing as a plug. Vol­ca­noes with highly vis­cous magma are tick­ing bombs. If the pres­sure keeps on ris­ing below the plug, the vol­cano will end up ex­plod­ing in an in­ferno of fire, glow­ing red-hot magma, and ash.

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