Cycloid. Marginated scales.
Debris. The fragments of rocks removed by the action of weathering or by water.
Decorticated. Stripped of bark.
Deflection. Deviation from a straight course.
Degradation. The wearing away of rocks, generally effected by aqueous action.
Deliquescent. Becoming fluid by the attraction of water from the atmosphere.
Delta. The alluvial land formed by a river at its mouth, usually expanded in a fan shape like the fourth letter of the Greek alphabet (Δ), and thence called Delta.
Denudation. The act of laying bare rocks formerly covered up, the removal of the overlying masses being effected by water.
Dermal. Belonging to the skin.
Detritus. Matter rubbed off by mechanical action from other rocks.