Black Rocks Protruding Up: The Navajo Volcanic Field
— Steven Semken

The mid-Tertiary-age volcanoes, dikes, and sills of the Navajo volcanic fi eld are classic and geologically-distinctive landforms of the Colorado Plateau. They are the products of structurally-controlled magma ascent, explosive eruptions, and deep post-eruptive exhumation. Igneous rock types include potassic lamprophyres, serpentinized tuffs, and exotic mafi c and ultramafi c intrusives. These rocks, along with a variety of crustal and mantle xenoliths that they have brought to the surface, have been used to map the petrology and history of the lithosphere and upper mantle beneath the Colorado Plateau. The landforms of the Navajo volcanic fi eld also fi gure prominently in the empirical knowledge and culture of the indigenous Navajo people.