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Vulcanii

Vulcanii.

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Vulcanii

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  1. Vulcanii

  2. Vulcanuleste de fapt o gaura in scortaterestra, prin care erup in aer gaze, cenusasirocisemitopite, care impreunaalcatuiesc lava. Partilecenusiivulcanice cad pe sol, se aseazastratificatsi se solidifica sub forma uneirociusoaresicenusii. In timpulmilioanelor de ani, acestestraturiformeazamuntiivulcanici. Deseorieisuntinalti, conici cu crater pevarfulconuluivulcanic. Multi dintreei se ridicapefunduloceanului.

  3. Vulcanii se formeaza in punctele de minima rezistenta ale scoarteiterestre. pamantulesteacoperit de o scoartadura, exterioara: litosferacompusadintr-o scoartasiparteasuperioara, dura a mantalei. Litosfera s-a fragmentat in placiuriase, rigide, asanumiteplacitectonice. Sub influentauriaseipresiuni din adancuri, placiletectonicesunt in permanentamiscare. In unelelocuriaceastamiscare da nastere la lanturimuntoase, alteorimarginileplacilor cad in santuriadanci, in adanculPamantului, fenomennumitsubdeductie. Placile in miscarecand se intalnesc, cand se indeparteazaunele de altele. Astefel de zone suntzonelemarginalealeplacilortectonice, fiind zone de minima rezistentapescoartaterestra, unde se pot produce eruptiivulcanice. Sub scoarta se afla un alt strat, mantaua, in interiorulcaruia, sub litosfera, la o adancime de peste 100km se aflaastenosfera. Aici se productemperaturiasa de mari, incatmulteroci se topesc. Acesterocitopite, care continsiapasi gaze, se numesc magma, care se aduna in camera magmatica. Magma e maifierbintesimaiusoaradecatmateriileinconjuratoare, iar in ascensiunespresuprafata, topeste mare parte din rocilestratului superior. In drumulspresuprafataianasterehornulvulcanului. Gazelesuntinchise in magma, crescandu-i presiunea. In final sub presiuneagazelor, magma erupe sub forma lavei in punctul de minima rezistenta a scortei.

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