The two major eolian mantles of Inland Northwest landscapes are loess and volcanic ash. Palouse loess covers ~10,000 square kilometers of the Columbia Plateau region and has been deposited episodically throughout the Pleistocene. The loess is derived from glacial sources and is of mixed mineralogy. Clay mica is the dominant clay mineral in the youngest loess soils, typically Haploxerolls and Argixerolls. In the next older loess paleosol, vermiculite is dominant, suggesting a mica-to-vermiculite weathering sequence. As such, clay mineralogy can be a useful tool in identifying paleosols. More recently, Holocene volcanic ash has influenced many mid- and high-elevation forested soils. Dacitic tephra from the cataclysmic eruption of Mt. Mazama has had the greatest overall impact on most soils across the region. Weathering of Mazama tephra has resulted in formation of allophane and ferrihydrite. Allophanic properties dominate in most of these soils. In some areas, replacement of forest vegetation by bracken fern has triggered a conversion to non-alllophanic mineralogy; active forms of Al3+ appear to rapidly shift from inorganic to organic phases. At higher elevations, podzolization is well expressed and results in the formation of beidellite the E horizons of Haplocryods.