Masonry near the ground surface can be severely damaged by the effects of poor drainage and repeated freezing and thawing. When these damaged stones can no longer support the weight of the wall above them, they are replaced with stones of similar size, shape, color, and surface texture. Replacing a few eroded stones at the base of a wall will protect the upper second and third stories of the building.
Did You Know?
The park considered a number of ideas for mitigating the damage that would be done if Threatening Rock fell. Proposed solutions included using dynamite to destroy it, anchoring it to the canyon wall with cables, or clearing out the rock debris behind it. It fell on January 22, 1941.