Regolith

noun (uncountable)

/ˈrɛɡəlɪθ/

The layer of loose, heterogeneous surface material — including soil, sediment, broken rock fragments, and weathered residue — that overlies consolidated bedrock on Earth, the Moon, and other planetary bodies. On Earth, regolith ranges from a few centimetres to hundreds of metres thick and is the medium within which pedogenesis (soil formation) occurs; on the Moon it is produced by meteorite impact gardening. The term is broader than 'soil' (which implies biological activity) and is significant for understanding the mineral exploration potential of weathered bedrock profiles in India's Deccan and Gondwana terrain.

✍️ Usage in a UPSC answer

The lateritic regolith of the Chhotanagpur Plateau, which can extend to depths of 30–50 m over Archaean basement rocks, hosts economically significant bauxite deposits exploited by NALCO and Hindalco for aluminium production.

Synonyms

mantle rockoverburdensaprolite (in-situ portion)driftsuperficial depositweathering mantle

Antonyms

bedrockfresh rockunweathered substrateconsolidated rock

🌱 Word Family

regolith (noun), regolithic (adjective), saprolite (related noun, in-situ weathered rock portion of regolith), pedolith (related term)

🔡 Root

Greek rhegos (variant rhegon) = blanket, covering + lithos = stone; so 'stone blanket'

📜 Etymology

Coined by American geologist George Perkins Merrill in 1897 in his work A Treatise on Rocks, Rock-Weathering and Soils, combining Greek rhegos (a blanket or covering) with lithos (rock/stone). Merrill needed a term to describe the universal layer of loose material overlying solid rock that he observed in weathering profiles across the United States. The term was later adapted in planetary science to describe the surface layer of the Moon.

🧠 Memory Hook

REGO-LITH = a BLANKET (rego = Greek for covering/blanket) of ROCK fragments (lithos = stone). The regolith is literally Earth's stone blanket — the loose, mixed layer draped over solid bedrock like a geological duvet.

🌍 Geography 📖 Seen in: Plate Tectonics & Volcanism — Continen...

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