What is tuff?

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Brian Campbell. Today's question is …

What is tuff?

Tuff is a volcanic rock made up of a mixture of volcanic rock and mineral fragments in a volcanic ash matrix. Wherever there are explosive volcanic eruptions you can expect to find tuff. Tuff forms when some combination of ash, rock and mineral fragments (pyroclastics or tephra) are blasted into the air, then fall to the ground as a mixed deposit. Most of the rock fragments tend to be volcanic rocks that were once solidified parts of the volcano that erupted to produce the tuff, but sometimes other types of rock are blasted out and incorporated into the tuff as well.

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