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the crest of the cliff and shows evidence of incipient movement. It poses a hazard because it <br />~• can be reactivated. <br />Planar Failures. Planar failures occur along ajoint or .fracture having a moderate <br />dip where the dipping plane is daylighted at a free surface. The dipping plane has an <br />adverse and potentially unstable orientation. The addition of water along the plane may <br />l induce sliding of the block. <br />1 <br />Such failures generally remain fairly close to the cliff face. Two such failures <br />were observed. Both show evidence of incipient movement and both aze adjacent to the <br />erosional re-entrants: one in Zone Sc and the other in Zone 6. Both have developed along <br />1 northeast striking, southeast dipping joints. These blocks have the potential for further <br />movement. <br />1 <br />Wedge Failures. Wedge failures occur at the intersections of shear joints or <br />l • fractures provided the axis of the intersecting plane is adversely oriented with respect to the <br />free surface. Addition of water along the joints increases pore water pressure and increases <br />the likelihood for movement. <br />Wedge failures generally do not move too far from the base of the cliff. If a <br />wedge failure occurs high on the cliff face, the dislodged block may bounce and roll down <br />the talus slope. Wedge failures may occur in all Hazard Zones. <br />J A fairly large area, comprising all of Zone 6 (See Figure 3), with intersecting <br />shear joints was seen high on the cliff. This area was not examined because of time <br />constraints and difficulty of access. Observations of this feature from a distance of about <br />` 1,500 feet suggested that parts of the cliff face spalled along the shear joints. <br />3.7 Debris Flows <br />Other potential hazards include debris flows, soil failures, and erosion. <br />1 • 13 <br />