Human activity has led to the reactivation of
portions of a Pleistocene landslide complex in The Dalles,
Oregon. Slope movements are in rocks of the Chenowith
formation: agglomerate, conglomerate, tuff breccia, sandstone,
and siltstone. Slope movements occur in at least
two distinct areas in The Dalles. At one, the shear surface
is defined by the contact between the Chenowith formation
and the underlying Columbia River Basalt. Data from inclinometer
readings at the other area fail to reveal a well-defined
shear surface. Slope movements in The Dalles cause
tens of thousands of dollars worth of damage annually and
may present a threat to human safety. So far there has been
little organized response to this hazard
