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[1] Stratigraphic data suggest that during the North Mono-Inyo eruption sequence of $1350 A.D. a series of strong earthquakes occurred near the end of the North Mono explosive phases and the beginning of the Inyo explosive phases. The temporal proximity of these events suggests the possibility of a causal relationship. Geological and geomorphic features of the Hartley Springs Fault are consistent with rupture of the fault during the eruption sequence. These features include steep central slope segments on several fault scarps and a fault scarp and stratigraphic offset since the deposition of $1200-year-old tephra. We hypothesize that the Inyo Dike, found by drilling underneath the main Inyo vents, neared the Hartley Springs Fault as it propagated southward from the Mono Basin circa 1350 A.D. We demonstrate that once the lateral distance between dike and fault was sufficiently small, the mechanical interaction between them could have triggered the slip observed on the fault. The slip, in turn, could have reduced the horizontal confining pressure in a region near the southern tip of the fault. The presence of the main Inyo vents in this region suggests that the reduction in confining stress was sufficient to allow magma to propagate to the surface. The results suggest that a volcanotectonic ''cascade'' of eruptions and earthquakes is a possible mechanism by which a large section of a range front or rift system can be activated because of the positive feedback provided by each element to continued activity.

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Front cover. View looking northwest along the Furnace Creek fault zone in the vicinity of Hole-in-the-Wall (far left center) and Red Amphitheater canyon (to right of picture). Death Valley is visible in the distance, with the Panamint Range (left) and Cottonwood Mountains (center and more distant) on the skyline. Color change in low hills in the middle ground, from rusty orange (freshwater limestone; right) to light yellow (gypsum-bearing playa claystone; left) coincides with the major strand of the Furnace Creek fault in area of picture. Knobby dark outcrop in foreground is rock-avalanche breccia, which is capped by bouldery Pleistocene alluvium. Photograph taken by C.J. Fridrich, U.S. Geological Survey.

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Morphological and chemical properties of soils developed on moraines of granitic composition, and forested with lodgepole pine, in Bear Valley, Idaho, change significantly with age and slope position. Soil development on Pinedale and Bull Lake moraine slopes of similar curvature and steepness was assessed at the summits, shoulders, backslopes, and footslopes of both catenas, and at the toeslope of the Bull Lake catena. Many soil properties show trends in development with both age and slope position. These properties include clay content, clay film development, color, plagioclase weathering, and dithionite-citrate-extractable iron (Fed). The degree of development of all these properties is greater on the Bull Lake catena relative to that on the Pinedale catena. This trend reflects increased soil development with age. On both catenas, development of soil properties is commonly highest at the footslope or toeslope sites and minimum at the backslope site. Downslope changes are attributed to both colluviation and pedogenic processes, including sorting of sediments during downslope transport, greater accumulation of eolian materials transported to downslope sites by surface processes, and greater in situ weathering of mineral grains at the footslope and toeslope sites.