Pronunciation: TUFF (as in "tough")
Description*: Tuff is a volcanic or volcaniclastic rock formed of material that accumulated on or around the volcano after an eruption. Tuff has a pyroclastic texture. Ash-fall tuff is a fine-grained rock composed of volcanic ash. Oth
er examples of tuff may have the look of a coarse breccia (or concrete with angular aggregate), with broken angular pieces of whatever was blasted out of the volcano or carried along in a pyroclastic flow.
Sometimes, older tuff layers can be metamorpho
sed by the heat and weight of subsequent tuff deposition into a dense silica-rich rock called a welded tuff.
*Description from Cronin, V.S., 2001, Geology laboratory projects for group learning: Primis McGraw-Hill, 156 pp., ISBN 0-07-252348-4
Used by permission of the author.
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