A smaller volcanic center lies several thousand kilometers west of Tharsis in Elysium. The Elysium volcanic complex is about 2,000 kilometers in diameter and consists of three main volcanoes, Elysium Mons, Hecates Tholus, and Albor Tholus. The northwestern edge of the province is characterized by large channels (Granicus and Tinjar Valles) that emerge from several grabens on the flanks of Elysium Mons. The grabens may have formed from subsurface dikes. The dikes may have fractured the cryosphere, releasing large volumes of ground water to form the channels. Associated with the channels are widespread sedimentary deposits that may have formed from mudflows or lahars. The Elysium group of volcanoes is thought to be somewhat different from the Tharsis Montes, in that development of the former involved both lavas and pyroclastics.