We thot that was the nicest outhouse as we drove by Black Rock Valley back to Highway 143 on Mammoth Creek Rd.

Some science from wiki: The Markagunt Plateau is part of the High Plateaus geologic province, in the Colorado Plateau and at its margins with the Basin and Range Province. It is a 37–50 mi wide fault-bounded block and the basement underneath the volcanoes is formed by various Cretaceous to Miocene sedimentary or volcanic rocks. Volcanism in the region has been ongoing for the last 5 million years. The volcanism is considered to be intraplate and unrelated to either mantle plumes or subduction.

Volcanic rocks at Markagunt Plateau are unusual for the common occurrence of subalkaline volcanics; most other recent volcanic centres in the Basin and Range Province have produced alkali basalts. Mixing between crustal melts and primitive magmas may explain this tendency, while the presence of tholeiite may indicate the occurrence of rifting processes in western Utah.