Principles Of Earth Science

INTERPRETING THE HISTORY OF VOLCANOES AND VOLCANIC ROCKSDrawing from the diagram , the volcanic interpretation is as outlined below and other relevant pattern out be also suppliedSequential summary of volcanic autobiography the argonaAndersite porphyry : this is the oldest . Andersite indicates magma of intermediate composition . Its silicon dioxide national is halfway between felsic rocks (having advanced silica sate ) and mafic rocks (having low silica content . Its giveation is a two-step process where slow temperature decline occurs at the initial stage within the crust forming self-aggrandising crystals as a result . However , the remaining magma moves further 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 irruption Turf grading into braccia : these are pyroclastic rocks formed by violent eruption of highly glutinous magma . The tuff is finer than breccia but the two are of the very(prenominal) detail of defining .

The magma forces its way out shattering the environ bendable 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 porous holes containing gases that were pi! n down within the forming magma at the onset of eruption . The gases later escapes to form a light , porous glassed rock . The breccia was likely to...If you want to get a abounding essay, order it on our website: BestEssayCheap.com

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