tuff


tuff

noun \ˈtəf\

Definition of TUFF

:  a rock composed of the finer kinds of volcanic detritus usually fused together by heat
tuff·a·ceous \ˌtə-ˈfā-shəs\ adjective

Origin of TUFF

earlier tuph, tuft porous rock, from Middle French tuf, from Old Italian tufo
First Known Use: 1815

Other Geology Terms

anthracite, boulder, cwm, erratic, igneous, intrusive, mesa, sedimentary, silt, swale

tuff

noun    (Concise Encyclopedia)

Relatively soft, porous rock that is usually formed by the compaction and cementation of volcanic ash or dust. Tuff may vary greatly not only in texture but also in chemical and mineralogical composition. In some eruptions, foaming magma wells to the surface as an emulsion of hot gases and incandescent particles; the shredded pumice-like material spreads swiftly, even over gentle slopes, as a glowing avalanche (nuée ardente) that may move many miles at speeds of 100 mph (160 kph).

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