Tuff

A close-up of the rock making the mini-badlands elsewhere in this album. It contains lots of rock fragments, probably glassy, that have some tendency to be parallel--"flow banded", in the jargon. A "tuff" is a volcanic rock deposited as individual particles out of a hot gas cloud. This is a "welded" tuff, meaning the particles were hot enough to weld into solid rock once they settled out. Such tuffs were once thought to be actual lava flows, till the work of geologist J. Hoover Mackin in the 50s, which appeared in the _American Journal of Science_ in 1960. It contains the memorable line, "Tertiary eruptions of the Great Basin would compare to those of modern times as the bursting of a firecracker to the explosion of a hydrogen bomb." You usually can't get language like that past the journals' referees!