Lake Manix, in south-central California, was the terminal basin of the Mojave River until the late Pleistocene, when it drained east to the Lake Mojave Basin. Based on new field observations, radiocarbon ages, and soil development, we propose modifications to previously published hypotheses on the timing of the last 543 m above sea level (masl) highstand of Lake Manix, the timing of the first discharge eastward, and the time required to cut Afton Canyon between the two basins. Subtle beach barriers, wave-cut scarps, and lagged beach gravels indicate that Lake Manix reached highstands between 547 and 558 masl at least twice prior to its previously known 543 m highstands. Properties of soils formed on beach barriers at 547–549 masl compared to soils on dated deposits suggest an age of older than 35 cal ka for this highstand. Calibrated radiocarbon ages for three lacustrine highstands at or near 543 masl are ca. 40–35 ka, 33–30 ka, and 27–25 ka. Lake Manix periodically discharged down a drainage presently located on the north rim of Afton Canyon at 539 masl. Soil development estimated from multiple buried soils within fluvial deposits and overlying fan deposits suggests that discharge was coeval with or somewhat older than the 547–549 m highstand, and that fluvial aggradation in this drainageway was followed by a period of relative landscape stability and episodic burial by alluvial-fan deposits. Strath terraces below these highest fluvial deposits, but above the canyon rim, record initial incision of the Lake Manix threshold. Surface and soil properties indicate that they are latest Pleistocene to early Holocene in age, similar to the previously studied strath terraces that are inset well below the rim and below the basal lake sediments. We suggest that the higher straths above the rim formed no earlier than ca. 25 cal ka. We interpret the soils, stratigraphy, and fluvial landforms in the canyon to indicate relatively rapid incision of Afton Canyon to the depth of the bedrock floor of Lake Manix, followed by intermittent, gradual bedrock incision.

Six dust plumes, arising from a Santa Ana wind and covering an area of 1,700 km 2 of the western Mojave Desert, were photographed by the National Aeronautics and Space Administration LANDSAT/ERTS-1 satellite on January 1, 1973. The cause of erosion was identified as man’s destabilization of the natural surface through road building, agriculture, urbanization, stream-channel modification, and off-road vehicle recreation. The extensive, and growing, destabilization of the California desert surface provides for ever-increasing dust yields in storms of the future.