Rock Classification Scheme (BGS).pdf - The Water, Sanitation and ...
Rock Classification Scheme (BGS).pdf - The Water, Sanitation and ...
Rock Classification Scheme (BGS).pdf - The Water, Sanitation and ...
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Figure 5 <strong>Classification</strong> <strong>and</strong>nomenclature of pyroclasticfragments <strong>and</strong> well-sorted pyroclasticsediments <strong>and</strong> rocks (after Schmid,1981).Fragment size Dominant pyroclastic Pyroclastic sediments Pyroclastic rocksin mm fragment6420.032bomb, blockbomb-tephrablock-tephraagglomeratepyroclastic-breccialapillus lapilli-tephra lapillistonecoarse ash grain coarse ash coarse tufffine ash grain fine ash fine tuffFigure 6 <strong>Classification</strong> of volcaniclastic rocks containing morethan 10% volcanic debris (based on Schmid, 1981).Averagefragment size Pyroclastic rocks Tuffites Volcaniclastic sedimentaryin mmrocksagglomeratepyroclastic-breccia64 tuffaceous-conglomerate volcaniclastic-conglomeratelapillistone2coarse tuff tuffaceous-s<strong>and</strong>stone volcaniclastic-s<strong>and</strong>stone0.032fine tuff tuffaceous-mudstone volcaniclastic-mudstoneAmount ofpyroclastic 100%–75% 75%–25% 25%–0%materialpumice, glassFigure 7 <strong>Classification</strong> <strong>and</strong> nomenclatureof tuffs <strong>and</strong> ashes based on their fragmentalcomposition (after Schmid, 1981).vitric tuffvitric ashcrystal tuffcrystal ashlithic tufflithic ashcrystals,crystal fragmentsrockfragments31
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