Rates of Weathering Layer Development: A Review of Studies on Weathering Rind, Weathering Crust, and Rock Varnish

Many researchers have studied rates of weathering layer development. Weathering layers broadly include weathering rinds, hydration layers, rock varnish, and weathering crusts, each of which has been discussed within individual research fields. To understand the development of these weathering layers, previous research on the growth rates of weathering layer thickness and formation processes is reviewed. Then, terminology relating to weathering layers is elucidated. Weathering rind development is affected by the porosity and mobility of many elements. Conversely, the obsidian hydration layer is mainly controlled by moisture content and rock varnish is influenced by microbial activities. Environmental differences in the thickness of these thin weathered or alteration layers with weathering time are also examined. Although data are limited, the growth of weathering rind thickness varies by rock types and environmental conditions. The next stage of weathering rind studies will be supported by the progress of analytical methods including isotopic elements, interpretation of rock properties, biomineralization, and introduction of environmental parameters.