Valles Caldera is the type locality for a resurgent dome caldera, the formation of which was first developed by C.S. Ross, R.L. Smith, and R.A. Bailey during field work at Valles in the 1960s. After the initial caldera forming eruption at Valles, the Redondo Peak resurgent dome was uplifted beginning around 1 million years ago. Eruption of moat rhyolitic lava domes occurred from approximately 1.04 million years ago to 0.13 million years ago along a structural ring fracture zone. The El Cajete Pumice, Battleship Rock Ignimbrite, and the Banco Bonito obsidian flow were emplaced during the youngest eruption of Valles Caldera, about 68,300 ± 1,500 years ago. The caldera and surrounding area continue to be shaped by ongoing volcanic activity. Seismic investigations show that a low-velocity zone lies beneath the caldera, suggesting the presence of partial melt within a remaining magma chamber at between 5 and 15 km depth. An active geothermal system with hot springs and fumaroles exists today. These calderas and associated volcanic structures lie within the Jemez Volcanic Field. This volcanic field lies at the intersection of the Rio Grande Rift, which runs north-south through New Mexico, and the Jemez Lineament, which extends from southeastern Arizona northeast to western Oklahoma. The volcanic activity here is related to the tectonic movements of this intersection.