Pine Canyon caldera complex

The Pine Canyon Caldera Complex is a 6–7 km (3.7–4.3 mi) caldera complex located in the southern part of the Chisos Mountains in the South Rim Formation in Big Bend National Park of Texas. It is a type of collapsed caldera called a downsag caldera, meaning it lacks surficial faulting. It was formed by several rhyolitic eruptions caused by crustal stretching during the Ouachita orogeny about 32 million years ago. The high magnetic waves present in the northern part of the caldera are believed to be from a broad intrusion, which indicates a partial crustal boundary of the Ouachita orogeny. This feature represents the largest intrusion, (24–38 km (15–24 mi), 1–4 km (0.62–2.49 mi) thick, 700–3,000 km³ (170–720 cu mi) in volume) in an area where laccoliths are ubiquitous. This intrusion may represent a long-lived magma chamber (1 m.y.) that was replenished by smaller batches of magma of varying viscosities.