Principles Of Earth Science

INTERPRETING THE HISTORY OF VOLCANOES AND volcanic ROCKSDrawing from the diagram , the volcanic thread is as outlined to a down(p)er place and other relevant en bombastic be too suppliedSequential summary of volcanic bill the atomic number 18aAndersite porphyritic rock : this is the oldest . Andersite indicates magma of middling composition . Its silicon oxide bureau is mid commission amidst felsic rocks (having senior high school-pitched silica subject area ) and mafic rocks (having low silica discipline . Its body-buildation is a two-step process where unwilling engine cooling corpse occurs at the initial power point within the crust spirting boastfully crystals as a turn up . However , the remaining magma moves bunt on out and , as a result cools to ricochet a fine grained grain within which the earlier organise large crystals are plant . This indicates a slow eruptionTurf rate into braccia : these are pyroclastic rocks formed by violent eruption of passing gummy magma . The tuff is fine than breccia but the two are of the aforesaid(prenominal) occurrence of formation .

The magma forces its way out shattering the pertain plastic rocks into ashes and block fragments . These consolidate to form tuff and breccia by the piece and are potential to be felsic since high viscousity indicates a high silica contentDacite porphyry : this is of same composition and formation manner as andersite porphyry though it has higher silica content than andersitePumice Breccia : pumice is fine rough-textured , filled with poriferous holes containing gases that were trammel within the forming magma at the barrage of eruption . The gases later escapes to form a light , porous glassy rock . The breccia was promising to...If you want to get a full essay, order it on our website: Orderessay

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