What does laccolith mean?
A laccolith is a large mass of igneous rock that has forced its way between pre-existing layers of sedimentary rock, commonly producing a broad dome. Its magma generally enters from below and spreads laterally without cutting across the surrounding strata, which it may lift and deform. The resulting body can be many kilometres across, so a laccolith may be regarded as a major structural feature rather than merely a small geological intrusion. Although the term is sometimes applied to smaller intrusive bodies, it most characteristically denotes a large, mushroom-like or dome-shaped feature. Laccoliths are important in the study of magmatism, mountain-building, and the deformation of sedimentary basins. The word is principally used by geologists and appears in specialist descriptions of granite intrusions and structural domes.
nounA large, typically dome-shaped mass of igneous rock intruded between existing rock layers without cutting across them.
- A dome-like body of igneous rock formed by magma intruding between and lifting up pre-existing rock layers.
"Geologists discovered a massive laccolith beneath the mountain range."
"The laccolith consists mainly of granite and has arched the sedimentary strata above it."
"Satellite images helped geologists identify the laccolith as a broad geological dome."
The standard plural of laccolith.
"Several laccoliths occur along the eastern edge of the range."
A laccolith is a stone intruder with a familiar shape: a buried mushroom whose magma never reached the sky.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of laccolith
The name combines Greek elements meaning “hollow” or “cistern” and “stone.” It was coined in the 19th century as a geological term for a particular kind of igneous intrusion, drawing on the rounded or lens-like form of the resulting rock mass. Its components are cognate with English words such as monolith, lithic, lithology, and lithium, all of which derive from the same Greek word for stone.
Related word forms
How laccolith is actually used
This is specialist terminology in geology. In general prose, it is rare, though it may occasionally be used metaphorically for a rounded or mound-like mass.