tuff: Quick Facts

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Yellowstone National Park: welded tuffs

A chart categorizes common textural terms for rocks by grain size in millimeters, dividing them into igneous and metamorphic, sedimentary, and pyroclastic types, with terms like phaneritic, sand, silt, breccia, and ash shown in relation to size.

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peperite ignimbrite ash-flow tuff welded tuff volcanic ash pyroclastic rock Mazama Ash agglomerate scoria agglutinate