OREGON STATE UNIVERSITY

Glossary beginning with R

Volcano Term Definitions

r
Rhyodacite

An extrusive rock intermediate in composition between dacite and rhyolite.

Rhyolite

Volcanic rock (or lava) that characteristically is light in color, contains 69% silica or more, and is rich in potassium and sodium.

Synonyms: rhyolites
Rift System

The oceanic ridges formed where tectonic plates are separating and a new crust is being created; also, their on-land counterparts such as the East African Rift.

Ring of Fire

The regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean.