blocks defined by tectonically induced joints and fractures may result in the formation of prominent and well-defined Liesegang rings within these blocks. These blocks typically consist of bedrock blocks (Liesegang blocks), which are bounded on their periphery by joints and fractures, and, in sedimentary rocks, bedding planes above and below. Each Liesegang block consists of a relatively unaltered core surrounded by concentric, alternating shells of iron-poor (intermediate shells) and iron-rich ('iron' shells) composition which make up the Liesegang rings. These iron-poor and iron-rich shells follow the configuration of the outer shape of the block and are sub-parallel to its sides. The iron-rich and iron-poor shells vary in degree of cementation and, as a result, can produce box work weathering structures during subsequent erosion. The degree of development of Liesegang rings as the result of weathering depends upon the spacing of the joint systems, groundwater flow, local topography, bedrock composition, and bed thickness. See also Exfoliation (geology), a related form of weathering that also creates domes. Exfoliating granite Weathering rind References External links E.H.Jager, (nd) Vulkanbomben, Wollsackverwitterung - interessante vulkanische Strukturen, Mögen Sie Pflanzen? Images of Spheroidal Weathering Swanson-Hysell, N. (2012) Featured Field Photo—Spheroidal weathering profile, Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA 94720 Geological processes Weathering fr:Chaos (géologie)#Chaos granitiques