Abstract

Morphological characteristics, erosional processes, and effects of burial and exhumation by debris mantles on basaltic volcanic landforms have been evaluated through field study of the Keanakakoi Formation, a basaltic tephra formed in 1790 by phreato-magmatic eruptions from Kilauea caldera, Hawaii. The upper coarse lithic, intermediate fine vitric, and lower mixed members of this formation play different roles in the creation of micro-terrain elements during stripping of tephra from the underlying bedrock. Of the seven micro-terrain elements defined, bedrock, scabby upland surfaces, and lag gravels are the most distinctive and widely distributed. Different proportions and combinations of micro-terrain elements define five zones of progressive deterioration of the Keanakakoi tephra blanket southwestward from Kilauea caldera into the Kau Desert. Fluvial and eolian processes operate on different time scales and at different locations, governed by blanket thickness, debris caliber, and the formation of case-hardened crusts. Stripping of an entire mantle is probably not possible; however, materials trapped within depressions form the only clearly discernible morphological expression of previously more extensive debris blankets.

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