Rhyolith

Rhyolith is a term used in geology to describe a small to medium-sized volcanic feature that is dominated by rhyolitic material. Rhyolite is a high-silica, highly viscous volcanic lava, and rhyoliths typically form in volcanic centers where rhyolitic magma erupts and thickens the crustal melt supply.

Morphology and formation

Rhyoliths may present as lava domes, coulees, or compact to thickly bedded pyroclastic masses that consolidate into dome-like forms. They often develop through steady effusion of viscous rhyolitic lava, inflation of a growing dome, and intermittent explosive activity that deposits pumice and other glassy debris. The resulting structures are characteristically steep-sided and may preserve glassy components such as obsidian or abundant pumice fragments. In some settings, rhyolithic deposits are part of larger silicic eruptive sequences that include tuff rings or caldera-related complexes.

Geologic significance

The study of rhyoliths helps illuminate eruption dynamics in silicic systems, magma viscosity, degassing processes, and crustal evolution. Their association with caldera-forming events and long-lived rhyolitic reservoirs makes them useful for reconstructing volcanic histories and dating volcanic activity in a region.

Terminology and scope

The term is used variably in the literature and can overlap with related concepts such as lava domes, rhyolitic tuffs, or pyroclastic deposits. As a result, precise usage can vary by region and author, and regional stratigraphic glossaries should be consulted for specific definitions.

See also: rhyolite, lava dome, silicic volcanism, tuff.