GeoMiner Free earth-science tools

Built by a geologist

Sill identification and geology

A tabular body of intrusive igneous rock that is concordant—parallel to the bedding or foliation of the surrounding country rock. Sills form when magma is injected along pre-existing planes of weakness bedding planes, foliation surfaces and crystallizes in place. They range from centimeters to hundreds of meters in thickness and can extend for many kilometers laterally. Field: petrology. Example: The Whin Sill of northern England is a dolerite diabase sill up to 70 m thick that was intruded into Carboniferous sedimentary rocks approximately 295 million years ago and forms the foundation of parts of Hadrian's Wall.. Related terms: Dike, Concordant, Intrusion, Laccolith.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.096023+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

Read GeoMiner's editorial methodology or report a content issue.

Common questions

What does Sill mean in geology?
A tabular body of intrusive igneous rock that is concordant—parallel to the bedding or foliation of the surrounding country rock. Sills form when magma is injected along pre-existing planes of weakness bedding planes, foliation surfaces and crystallizes in place. They range from centimeters to hundreds of meters in thickness and can extend for many kilometers laterally.
What is an example of Sill?
The Whin Sill of northern England is a dolerite diabase sill up to 70 m thick that was intruded into Carboniferous sedimentary rocks approximately 295 million years ago and forms the foundation of parts of Hadrian's Wall.
Which earth-science field uses the term Sill?
Sill is used in petrology.
Which terms are related to Sill?
Related terms in this reference are Dike, Concordant, Intrusion, Laccolith.

JavaScript is loading the interactive GeoMiner experience. The identification tools provide educational candidates, not laboratory confirmation.