Glossary of Volcanic Terms

Photo of a person in the field investigating a volcanic crater.
A scientist from the Hawaii Volcanoes Observatory monitoring gas emissions at Mauna Loa (2005).

USGS photo.


Every professional field has its own specialized language, and the study of volcanoes, volcanic processes, volcanic rocks, and volcanic deposits is no different.

The terms in this glossary are adapted when possible from the glossary of geologic terms for Geologic Resources Inventory (GRI) publications. The glossary of geologic terms is largely based on definitions in the Glossary of Geology, 5th edition.

Some definitions in the GRI glossary were adjusted in order to be specific to volcanic resources. Many volcanic terms that are not in the GRI glossary were added to this one. The definitions in this glossary match how the terminology was used throughout the NPS volcanoes subject site.

Volcano Glossary

Volcano Glossary
Word Definition


Terms in the volcano glossary were prepared to accompany the Volcanoes, Craters & Lava Flows website. Primary sources, include:

Last updated: May 22, 2024