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- 28 - fan, and instead is characterized by a hummocky, poorly drained surface and occasional sizeable closed depression features which form boggy areas or ponds. This feature appears to be older than the main mudflow fan and, except for the probable landslide scarp (3e), shows no indica- tions of large fairly recent movements. Relative to possible construc- tion in the area of the old landslides, we have the same general obser- vations made concerning the mudf10w fan areas. Much of the area is poorly drained, there is locally very steep topography, and the material is primarily disintegrated and broken shale which could be easily mobilized by addition of ' water and disturbance from construction activities. A more serious implication of the extensive old landslide debris below Gallo Bluff is that it suggests large scale and catastrophic rock- fall or debris avalanche events may occur periodically in the history of the bluff. If this is the case, the area for a considerable distance in front would be subject to severe devastation. Large scale events of this sort probably explain the large area of landslide terrain described above. We believe that the present extent of landslide materials is a combination of original very large landslides from the bluff, followed by subsequent movement of part of the originally displaced mass by less spectacular sliding at lower topographic levels. This is our interpre- tation of the scarp (3e) described above which appears to be more recent than the main landslide. On the strength of the above geologic evidence, we strongly suggest that if this area is to be developed, a wide setback should be observed from the base of Gallo Bluff, and that any construc- tion in the area of the old landslide terrain should proceed only after thorough engineering geology and soils engineering studies.