Southwest of previous volcanic fields, the Red Hills volcanic field consists of young volcanic structures, surrounded by mesas capped with basalt, and located near the border with Arizona and Springerville field.
The maar Red Hill:
Red Hill cone, formed of red cinder is morphologically altered more than other basaltic cones dating from 300,000 years of Springerville field, and less than those dated of 800,000 years ... which gives it an age of about 500,000 years.
Major lava flows associated are olivine basalts, with Pressures ridges.
The maar Red Hill is an example of a maar associated with faults and a fissure volcanic activity. The maar and a small elongated to the south vent are aligned parallel to the fault scarps involving a stress different of the Springerville field.
A small cinder cone occupies the floor of the maar. The ash, interbedded with deposits of maar beds, suggest a departure from the eruption with ash and pyroclastic activity occurring, which has evolved to more explosive eruptions of maar type, then return to the primitive type.
The maar of Zuni Salt Lake is part of a complex of cones and maars aligned on a fracture zone of 60 km. The lake is about 1,895 m. high.
Beautiful photos of maar on:http://www.airphotona.com/image.asp?imageid=4031
A period of surtseyan activity with continuous phreatomagmatic surges, which established a tuff ring; ash particles are highly altered in palagonite, and the presence of accetionned lapilli is observed. It was followed by intermittent Strombolian explosions and ash deposits found up to 8 km. of the salt Lake. Finally, building a cinder cone is explained by the introduction of a basaltic dyke ring that accessed the surface to give spatter and short lava flows. Maar subsidence occurred during the eruption, and the edge of the crater was at the end of the eruption at 30 meters above the surrounding terrain. The climate, wettest at the eruption time, allowed the crater to fill; diatoms, ostracods and gastropods have been dated by C14 to 22,900 + / - 1400 years.
The climate is then dried by reducing the area of the lake by a third, and is home of bacteria, algae and crustaceans Artemisia salina.
The Indians used the salt for at least 1,000 years, and in modern times, it was harvested for animal use, metallurgy, and road salting.
- New Mexico museum of natural history and sciences - Red Hill volcanic field - link
- Quaternary basalt fields of west-centralNew Mexico … Zuni canyon aa flow, Zuni Salt lake maar – by W.E.Elston & K.H.Wohletz - link