Much of Bryce Canyon Country’s unique landscape reflects an interesting volcanic history. Exposed geology reveals ancient lava deposits. and large lava fields on the Markagunt Plateau show evidence of volcanic activity as recent as one thousand years ago.
One of the most significant areas of volcanic activity in the Bryce Canyon region is the Markagunt Plateau, beginning about 5 million years ago. The latest eruption occurred around 1,000 years ago, based on the study of growth rings of some of the oldest juniper trees in the flow. Some of the youngest lava fields and cinder cones are located near Panguitch Lake, including a large block of lava flow that reaches from Miller Knoll almost to the lake. About 22 miles south of Panguitch Lake, Mammoth Cave is a lava tube that was formed by water and cooling lava. The 1/4-mile-long cave, formed about 2,000 years ago, is one of the largest lava tubes in Utah.
Twenty miles northwest of Bryce Canyon National Park, the Marysvale volcanic field is one of the largest volcanic fields in the western U.S. A variety of volcanic features including lava domes, cinder cones and stratovolcanoes are believed to be up to 30 million years old. The Marysvale volcanic field actually collapsed under its own weight about 20 million years ago, altering the geography. Volcanic activity around Marysvale and Bryce Canyon ended about half a million years ago. It is likely that the lava was also once deposited in Bryce Canyon but it has disappeared through erosion.
Volcanoes are formed by molten magma forcing its way through from deep below the crust. The often cone-shaped formations have wide center openings through which molten lava, rock, gas, steam, and ash expel from deep below. Mammoth Cave is believed to have been formed by lava pushing up through fissures in the earth. Millions of years of plates sliding, lifting, and melting led to the formation and eruptions of ancient volcanoes in the area now known as Bryce Canyon Country.