The Post Up a Rock on Tuesday thread.

are those silt clays what makes for good potato dirt or maybe aeolian deposits?

Throughout this area, the Yahoo Clay is monotonously uniform in its lithology,consisting of laminated clay and sparse amounts of
silty clay.
The clay is compact and
hard when dry, breaking with a conchoidal fracture,
but readily slakes in water. The eroded surface
weathers to form a loose, “popcorn” surficial layer a
foot or more thick, possibly because of the presence
of clays that swell when wet.

Fault displacement that produced this intense earthquake was expressed in spectacular surface ground rupture along a northwest-trending, 22 mile-long zone on the western flank of the Lost River Range. A west-northwest-trending section of faulting that branches off of the main surface fault trace west of Dickey Peak gives the surface faulting pattern a Y-shape. Much of the zone of surface rupture follows the Holocene and upper Pleistocene fault scarps of the Lost River fault. Fault scarps, the most common features along the zone of surface faulting, look like small steps or cliffs. Fault scarps are produced when adjacent blocks of the earth's crust move relative to each other and are displaced along a fault plane.

“Lawana Knox of Challis, Idaho, witnessed the for-mation of a fault scarp during the Ms 7.3 earthquake of 28 October 1983 along the Lost River Range, Idaho. The earthquake occurred at 8:06 a.m. local time (1406 UTC) while Mrs. Knox was hunting with her husband, William Knox.

Mrs. Knox was sitting at a point along a fork of Arentson Gulch…and was watching the southwest-facing slope down which she expected to see her husband driving elk. As she watched, the fault scarp formed before her eyes. At the closest point, the scarp was about 300 m away, but she could clearly see the scarp for at least 1 kilometer both to the northwest and to the southeast.

Mrs. Knox reported that the 1- to 1.5-m-high scarp formed in about 1 second. She reported that the scarp reached its full height quickly, and that it did not appear to adjust up or down later or oscillate up and down while reaching its full height. Mrs. Knox reported that the scarp did not form until the peak of strong shaking was beginning to subside.

Upon being asked how long the strong shaking lasted, Mr. Knox replied, “about a minute.” Mrs. Knox disagreed and said, “it might have been a half a minute, but it felt like a lifetime.” Both Mr. and Mrs. Knox said the earthquake started with noise and that “the earthquake came from the south, from the direction of Borah Peak.” After the first sensa-tions, the ground shook harder and harder, and only after the shaking started to subside or ease did Mrs. Knox see the scarp form.”—from Wallace (1984)