Gemini color photographs of the Peruvian coast reveal fan-shaped patterns of eolian sand sheets emanating from small bays and extending inland 20-40 km. The sand sheets are spaced at regular intervals, and each comprises a distinct sand-distribution system with recognizable components. A 1968 field program investigated form-process relations between sand sheets and the sea-breeze phenomenon.

Most sheets are supplied by marine sand transported from source areas by along-shore currents, deposited on beaches, and blown inland in high-velocity sea-breeze zones. The winds, and consequently the transported sand, are directed and twisted by hills and valleys and in places execute turns of 120°. Locally, sands reach elevations of 2,000 m, forming giant sieflike dunes that "climb" over hilltops. In some places, sands spiral inland toward nuclear areas. Spiral centers coincide with centers of sea-breeze convection cells and form terminal points of sand transport. There dunes reach maximum development.

High-velocity sea-breeze zones are separated by lower velocity zones. In low-velocity zones, dust mantles hills, and eolian sand movement is absent. In some

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high-velocity zones, marine sand is not available for transport. There bedrock sand and dust, largely a product of intensive marine-desert chemical weathering, are wind transported, resulting in either sand sheets or deflation areas.

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