暗色岩

Trap \Trap\, n. [Sw. trapp; akin to trappa stairs, Dan. trappe,
G. treppe, D. trap; -- so called because the rocks of this
class often occur in large, tabular masses, rising above one
another, like steps. See {Tramp}.] (Geol.)
An old term rather loosely used to designate various
dark-colored, heavy igneous rocks, including especially the
feldspathic-augitic rocks, basalt, dolerite, amygdaloid,
etc., but including also some kinds of diorite. Called also
{trap rock}.

{Trap tufa}, {Trap tuff}, a kind of fragmental rock made up
of fragments and earthy materials from trap rocks.