noun Download 🔗Share The old geological theory that the rocks forming the Earth were formed in fire by volcanic activity, with a continuing gradual process of weathering and erosion, then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again. Examples : "The old geology textbook explained plutonism as the way volcanic activity deep within the earth formed rocks, which then eroded and reformed into layers over time. " geology theory science history Chat with AIVocabulary GamePractice Reading