Characterization of shield volcanoes on Earth and Mars from lava slope analyses and lava flow mapping

Slope frequency and hypsometric analyses were used to study Shuttle Radar Topography Mission data for the subaerial Hawaiian shields. Slope frequency results show an increase in median slope related to increased shield age. Hypsometric analyses show that the Hawaiian shields maintain consistent upward and lateral growth until alkalic capping and subsidence alter the relief-surface area ratio. Changes in the morphometry of the Hawaiian shields are related to decreased partial mantle melting and magma production rates at older shields. The internal dynamics act to decrease the steadiness and duration of magma delivery to the surface causing a decrease in buffered eruptions, dike intrusions and rift zone activity, and formation of lava tubes, all of which contribute to an increase in slope and relief-surface area ratios.; Lava flow mapping of the European Space Agency's Mars Express High Resolution Stereo Camera images over a north-south transect of the martian volcano Olympus Mons (OM) is compared with Hawaiian results to provide insight into its development. OM shows a 5:1 ratio between lava channels and tubes. Younger channels embay tubes, suggesting a transition from stable, tube-forming eruptions to less stable, channel-forming eruptions. A similar transition results from decreased magma production at Hawaii, suggesting that the magma source for OM has cooled through time. No eruptive vents were identified, indicating rift zones have not developed.; Similar mapping conducted for the Tharsis Montes (Arsia, Pavonis, and Ascraeus Montes in order of decreasing age), a chain of shield volcanoes across the Tharsis Province on Mars, shows that their main flanks experienced a similar transition from which no trends can be identified between the shields. Unlike other martian shields, the Tharsis Montes show parallel-trending rift zones that emplaced vast lava plains. Mapping of the rift aprons shows an increase in lava tubes, and satellitic eruptive vents, and a decrease in channel-tube ratios, apron volumes, and apron elevations towards the northeast. Results suggest that the eruptive history of the Tharsis Montes involves a complex interaction of broad mantle upwellings.