Malpais maar Volcano
— Richard O. Page

Malpais maar is a Quaternary tuff ring, similar to the well-known Kilbourne, Hunts' and Potrillo maars (Reeves and De Hon, 1965) formed by phreatomagmatic eruption of alkalic olivine basalt at the southern margin of the Potrillo basalt field, southcentral New Mexico (Fig. 1). The vent penetrated shallow aquifers or water-saturated surficial sediments or both, and began eruption as a maar volcano, depositing up to 50 ft (15 m) of bedded hyaloclastic debris over the surrounding area. During eruption, water was excluded from the vent, and the style of eruption changed to lava fountaining and tephra production, constructing a cinder cone and flow complex within the crater. Late stage activity included extrusion of parasitic lava flows, intrusion of dikes into the bedded tuff sequence, and eruption of a small parasitic, maar-type vent (Fig. 2).