Principles Of Earth Science

INTERPRETING THE HISTORY OF VOLCANOES AND VOLCANIC ROCKSDrawing from the diagram , the volcanic account is as outlined below and other relevant name out be also suppliedSequential summary of volcanic storey the beaAndersite porphyry : this is the oldest . Andersite indicates magma of intermediate composition . Its silicon oxide national is midway between felsic rocks (having advanced silicon dioxide sate ) and mafic rocks (having low silica content . Its giveation is a two-step process where slow temperature decrease occurs at the initial stage within the crust forming expectant crystals as a result . However , the remaining magma moves farther out and , as a result cools to form a fine grained texture within which the earlier formed turgid crystals are embedded . This indicates a slow rushTurf grading into bracci a : these are pyroclastic rocks formed by violent eruption of highly pasty magma . The tuff is finer than breccia but the two are of the very(prenominal) event of makeup .

The magma forces its way out shattering the environ ductile rocks into ashes and block fragments . These consolidate to form tuff and breccia one by one and are probably to be felsic since high viscousity indicates a high silica contentDacite porphyry : this is of similar composition and formation modality as andersite porphyry though it has higher silica content than andersitePumice Breccia : pumice is fine textured , filled with holey h oles containing gases that were pin down wi! thin the forming magma at the onset of eruption . The gases later escapes to form a light , porous shiny rock . The breccia was likely to...If you want to get a respectable essay, order it on our website: BestEssayCheap.com

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