Volcanic Caldera

Large cauldron-like volcanic depression formed when a magma chamber empties and its roof collapses along ring faults.

Specifications & Metrics

type: Surface & Volcanic Landform
tectonic regime: Magmatic Evacuation & Ring-Fault Subsidence (explosive silicic or effusive basaltic)
typical scale: 1.6 to 100 km in diameter (e.g., Lake Toba 100 × 30 km; Yellowstone 55 × 72 km)
characteristic lithology: Welded ignimbrite ash-flow tuffs, rhyolite domes, or shield-summit basalts
examples: Yellowstone Caldera, Lake Toba, Valles Caldera, Crater Lake (Mount Mazama), Tambora

Introduced into geology by Leopold von Buch after visiting the Canary Islands in 1815, a caldera forms not by explosion excavating a crater outward, but by the roof of a magma chamber subsiding downward along circular ring faults as magma is evacuated.
Silicic explosive calderas such as Lake Toba (~2,800 km³ erupted ~74,000 years ago), Yellowstone (~1,000 km³ Lava Creek Tuff), and La Garita (~5,000 km³ Fish Canyon Tuff) blanket continents in ash-flow ignimbrites and often uplift central resurgent domes.
Circulating hydrothermal fluids driven by residual magmatic heat along caldera ring fractures concentrate epithermal ore deposits of gold, silver, lead, mercury, and lithium.