Block tectonics has uplifted or sunken crustal blocks. Eon corresponds to a period of increasing crustal recycling, suggesting subduction. Volcanism appears to be associated with crustal extension at Erciyes. The origin of the volcanism is unknown, but is probably related to crustal thinning. The subsidence was the result of a combination of crustal stretching, cooling, and loading. There are fissures, plains, corrugated terrain and other crustal deformations. Numerical models of crustal heating confirm slow cooling in the deep crust. The southern highlands of Mars display zones of intense crustal magnetization. Rifts are linear zones of localized crustal extension. This is comparable to the crustal abundances of lead, cobalt, and niobium. Smaller features are attributed to crustal anomalies. Accommodation zones may be located where older crustal structures intersect the rift axis. Lateral variation of the crustal density should exist. Methane is ubiquitous in crustal fluid and gas. Such thickness is critical in maintaining hemispheric crustal variations and preventing channel flow.