Pancake domes — Introduction
Pancake domes are a distinctive class of volcanic edifice found on Venus, representing a morphotype unique to Venusian volcanism. Individual examples, notably the Carmenta Farra group, illustrate their characteristic form. These domes are broadly scattered across the planet, typically occurring in clusters; however, such clusters contain fewer individual domes than the more extensive groupings associated with Venusian shield volcanoes. Spatially they are most common in lowland plains and frequently occur near coronae and tesserae, the latter being extensive, multiply deformed regions of folded and fractured terrain considered a Venus-specific geological unit. Pancake domes are anomalously large relative to terrestrial lava domes—on the order of 10 to 100 times greater in scale—which points to fundamentally different eruptive styles, magma rheologies, or emplacement conditions on Venus compared with Earth.
Description
Read more Government Exam Guru
Pancake domes are characterized by an extremely flattened, disc‑shaped morphology: they are broad, low‑relief volcanic edifices with a very small height‑to‑diameter ratio. In plan and slope they may resemble shield volcanoes, but their profiles are markedly thinner, reflecting a formation process dominated by lateral spreading rather than pileup of steep flows.
Their genesis is attributed to a single, protracted effusive event involving highly viscous, silica‑rich magmas (for example rhyolitic to dacitic compositions). High magma viscosity and slow extrusion rates favor the outward spread of coherent lava rather than construction of steep flanks, so the bulk of the deposit accumulates as a thin, wide sheet.
Emplacement proceeds by low‑rate outpouring of viscous lava that continues to deform while cooling; solidification, thermal contraction and ongoing lateral flow together set the dome’s final outline and internal stress regime. Many pancake domes develop a centrally located bowl or pit that resembles a crater externally but commonly forms after emplacement through cooling‑induced subsidence, degassing and interior collapse rather than representing the primary vent.
Free Thousands of Mock Test for Any Exam
Surface fabrics typically include dense networks of small fractures and faults, often organized into concentric and radial sets. These patterns record differential cooling, thermal contraction and mechanical readjustment (including subsidence or deflation) during and after the lava became coherent. Collectively, the flattened form, evidence for post‑emplacement central collapse, and the characteristic crack/fault patterns distinguish pancake domes from shield volcanoes and provide diagnostic information on eruption dynamics, magma rheology, and post‑eruptive cooling and degassing histories.