Black Rock Desert Volcanic Field

Summary

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The Black Rock Desert volcanic field is the northernmost volcanic field in a belt of young volcanic fields beginning in the northern Grand Canyon of Arizona and continuing in a north-trending line through Utah. Part of the eastern Basin and Range Province, the Black Rock Desert volcanic field covers nearly 7,000 km² (2,700 mi²) and is 145 km (90 mi) long. Black Rock Desert has been active for over six million years but has only been continuously active since 2.7 Ma. The first eruptions occurred in the north, forming the Topaz Mountain rhyolite lava domes and North Butte basalt flow at around 6.1 Ma. The latest eruptions took place in the central portion of the volcanic field about 10,000 years ago and formed the basalt cinder cones and flows of Ice Springs. Black Rock Desert is distinct from most other young volcanic fields in Utah in that it contains not only basalt and andesite, but also dacite and rhyolite. Eruptions are dominantly monogenetic, but some are more complex. Black Rock Desert is host to a variety of volcano types, including cinder cones, shield volcanoes, lava domes, maars (explosion craters), and a caldera. Lava tubes are preserved in some of the younger volcanoes.

The Black Rock Desert volcanic field is host to two other interesting features unrelated to volcanism: the presence of ubiquitous petroglyphs and the presence of shorelines engraved in the rocks, which are from the ancient Lake Bonneville. Lake Bonneville, present in Black Rock Desert from around 22,000 to around 12,000 years ago, is related to the Pleistocene Ice Ages. Erosional processes from shoreline action and deposits from the ancient lake remove or hide evidence of volcanic vent deposits, such as cinder cones, for all but the youngest eruptions. Petroglyphs are commonly found near old Lake Bonneville shorelines on boulders of basalt.