“…In addition to the large structures, there are countless low shields hundreds of meters high and several to tens of kilometers wide (e.g., Sakimoto et al, 2003;Hiesinger and Head, 2002). Aspects of Tharsis volcanism have been studied by many investigators and most of the constructs have been the subject of specific investigations (e.g., Crumpler and Aubele, 1978;Greeley and Spudis, 1981;Cattermole, 1990;Hodges and Moore, 1994;Morris and Tanaka, 1994;Plescia, 1994Plescia, , 2000Scott and Zimbelman, 1995;Scott et al, 1998).…”