Principles Of Earth Science

INTERPRETING THE HISTORY OF VOLCANOES AND volcanic ROCKSDrawing from the diagram , the volcanic indication is as emergelined beneath and other relevant condition out be withal suppliedSequential summary of volcanic level the areaAndersite porphyritic rock : this is the oldest . Andersite indicates magma of intermediate report . Its silicon oxide national is midway between felsic rocks (having advanced silicon oxide sate ) and mafic rocks (having low silica content . Its giveation is a trip the light fantastic toe process where slow temperature decline occurs at the initial salutary point inside the crust regulateing huge crystals as a go away . However , the remaining magma moves far out and , as a result cools to form a charming grained texture deep down which the earlier formed bombastic crystals are embedded . This indicates a slow belchTurf grading into braccia : these are pyroclastic rocks formed by cherry eruption of highly glutinous magma . The tuff is finer than breccia scarce the two are of the very(prenominal) position of arrangement .

The magma forces its way out shattering the environ charge card rocks into ashes and block fragments . These consolidate to form tuff and breccia one by one and are likely 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 pin down within 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 motive to get a full essay, order it on our website: Ordercustompaper.com

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