OREGON STATE UNIVERSITY

Glossary beginning with I

Volcano Term Definitions

i
Ignimbrite

The rock formed by the widespread deposition and consolidation of ash flows and Nuees Ardentes. The term was originally applied only to densely welded deposits but now includes non-welded deposits.

Intermediate

A descriptive term applied to igneous rocks that are transitional between basic and acidic with silica (SiO2) between 54% and 65%.

Intrusion

The process of emplacement of magma in pre-existing rock. Also, the term refers to igneous rock mass so formed within the surrounding rock.