Tharsis Tholus: an unusual martian volcano

Abstract

Tharsis Tholus is unusual martian shield volcano in that the edifice is cut by a series of large normal faults that appear to penetrate the entire volcano. Northeast-trending narrow graben also cut the flank. The large normal faults may be caused by loading of a ductile subsurface layer allowing failure of the edifice; the narrow graben are typical tensional faults. The flank is heavily mantled by aeolian material. Despite the bulbous appearance, the overall morphology of Tharsis Tholus suggests it is a basaltic shield. Crater counts indicate an age of early Hesperian placing Tharsis Tholus in the middle of the period of activity that built the other small Tharsis volcanoes. Published by Elsevier Inc.

Morphometric properties of Martian volcanoes

“…The geology of the Uranius Group (Uranius Patera, Uranius Tholus and Ceraunius Tholus) in northeast Tharsis was summarized by Plescia [2000], who also included estimates of the relief and volumes. South of this group and east of the Tharsis Montes lies Tharsis Tholus [ Plescia , 2003]. In most cases the relief, volume and slopes estimated here are similar to earlier estimates, some of which were in part based on early MOLA data.…”

“…Tharsis Tholus (Figure 12) lies on the eastern flank of Tharsis, south of the Uranius Group [ Plescia , 2003]. It is unique among the Martian volcanoes in that the flanks are broken into blocks by large normal faults [ Robinson and Rowland , 1994].…”

Arecibo radar imagery of Mars: The major volcanic provinces

“…Such a thick mantling is consistent with the radar darkness of the shield. Both Plescia (2003a) and Platz et al (2009Platz et al ( , 2011 have the shield surrounded and partly buried by younger and less heavily mantled lavas, which is consistent with the radar imagery. The radar image (Fig.…”

“…Viking and MOC images show a smooth shield devoid of individual flow features (Hodges and Moore, 1994;Plescia, 2003a), while some THEMIS and Viking images show linear features suggestive of heavily mantled lava flows (Plescia, 2003a). A heavy mantle is consistent with the low thermal inertia of the shield (Plescia, 2003a). A thick mantle was also proposed by Platz et al (2009Platz et al ( , 2011, who attribute the layer to dust and/or ash.…”

“…The entire heart-shaped shield is radar-dark except for a bright glint off the major fault that intersects the west rim of the caldera. Viking and MOC images show a smooth shield devoid of individual flow features (Hodges and Moore, 1994;Plescia, 2003a), while some THEMIS and Viking images show linear features suggestive of heavily mantled lava flows (Plescia, 2003a). A heavy mantle is consistent with the low thermal inertia of the shield (Plescia, 2003a).…”