Utah possesses an extensive geological history of volcanism, particularly across the western and southwestern parts of the state. The landscape is dotted with hundreds of features resulting from past eruptions, though they are not the massive, snow-capped peaks often imagined. Understanding the number of volcanoes in Utah requires focusing on a collection of smaller, distinct eruptive centers. This volcanic heritage is a direct consequence of the tectonic forces that have shaped the American West.
Defining Utah’s Volcanic Landscape
Utah’s volcanism is characterized by numerous volcanic fields rather than large, centralized structures, making a simple count difficult. These fields are composed of monogenetic volcanoes, meaning each vent typically erupted only once before becoming permanently inactive. This contrasts with the polygenetic stratovolcanoes, like those in the Cascade Range, which erupt repeatedly from a single main vent.
Geologists recognize several major young volcanic fields across Utah, primarily in the western Basin and Range Province and along the Colorado Plateau boundary. The number of individual eruptive centers within these fields totals in the hundreds. Southwestern Utah alone contains dozens of distinct cinder cones, lava vents, and associated structures.
These features include cinder cones, which are small, steep-sided hills built from fragments of ejected lava, and extensive basaltic lava flows. Counting these individual vents—the true number of “volcanoes”—is a complex tally that grows as new features are mapped. These fields represent the surface expression of magma rising through cracks in the Earth’s crust.
Key Regions of Volcanic Activity
Black Rock Desert Volcanic Field
The Black Rock Desert Volcanic Field, located near Fillmore, is the youngest and most prominent volcanic area. This field hosts diverse landforms, including cinder cones, shield volcanoes, and maars (explosion craters). The Ice Springs flow, the state’s most recent lava flow, occurred approximately 660 to 720 years ago.
Specific features here provide evidence of ancient lake interactions. Pahvant Butte and Tabernacle Hill are examples of tuff cones, which formed when rising magma interacted explosively with the water of ancient Lake Bonneville. The Ice Springs cones and their associated black basalt flows remain largely unvegetated, illustrating the youth of the eruption.
Markagunt Plateau Volcanic Field
Southwestern Utah is home to the extensive Markagunt Plateau Volcanic Field, situated east of Cedar Breaks National Monument. This field contains between 40 and 50 cinder cones and numerous lava flows. Navajo Lake was created when a lava flow dammed Duck Creek, demonstrating a notable result of this volcanism.
The Markagunt Plateau also features Mammoth Cave, one of the longest lava tubes in the state. This cave is a remnant of a fluid lava flow that solidified on the outside while the molten rock inside drained away. The youngest eruptions in this region, near Panguitch Lake, are estimated to be about 1,000 years old.
Current Status and Geological History
Utah does not currently have any volcanoes classified as active, but several young volcanic fields are considered dormant. Dormant fields have erupted within the last 10,000 years and could erupt again. The Black Rock Desert field has the highest threat potential due to the recent Ice Springs eruption.
Geologists monitor these areas using seismometers to detect small, shallow earthquakes that signal the movement of magma. A sequence of shallow earthquakes was detected beneath the Black Rock Desert in 2018 and 2019, confirming the area remains geologically dynamic. The potential hazards are mainly from new lava flows and the explosive formation of new cinder cones or maars.
The fundamental cause of volcanism in Utah is the ongoing extension of the Earth’s crust, which defines the Basin and Range Province. As the crust stretches and thins, it creates deep fractures and faults. This extension reduces the pressure on the hot mantle rock beneath, allowing it to partially melt and form magma that rises to the surface. This process, combined with the uplift and rotation of the adjacent Colorado Plateau, perpetuates the state’s history of basaltic volcanism.