36 Planetary Geology: A Solar System Tour

Sunday, 16 October 2005
1:30 PM - 5:30 PM

EVOLUTION OF EFFUSIVE STYLE AT PAVONIS MONS, MARS, INFERRED FROM LAVA FLOW MAPPING OF MARS EXPRESS HIGH RESOLUTION STEREO CAMERA DATA

Paper number: 36-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

The abundances and temporal relationships of lava channels and tubes can be used to infer recent styles of effusive activity on a volcano, as they generally form from different eruptive conditions. The southern flank of Pavonis Mons (PM), as imaged by the High Resolution Stereo Camera (HRSC), displays a higher ratio of channels to tubes than Olympus Mons (OM), with few, if any, tubes located near the summit. This suggests that either PM never experienced abundant tube-forming eruptions, or that the volcano experienced a transition from tube- to channel-forming eruptions, as seen at OM. Hawaiian shields display a similar transition, where older shields have lower abundances of tubes. Following the emplacement of flank flows from the PM summit, NE oriented rifting developed a new source region midway down the flank, producing a volcanic apron-shaped terrain to the southwest. The rift apron lacks lava tubes and is dominated by channels that are less subdued or buried than the flank channels. This channel-dominated, rift style of effusion appears to have transitioned to plains-style volcanism, superposed over the southeastern portion of the rift apron. This plains-style lava field is composed of >31 low shields and fissure-fed flows. The plains flows were emplaced via a combination of lava tubes and channels, surrounding the low shields and maintaining a slope below 1 degree, while the channel dominated portion of the apron displays slightly higher slopes. This transition in effusive style likely represents a change from major shield building to the plains-style volcanism that helped form the eastern Tharsis Rise. Preliminary crater counts for one low shield yield a model age of 100-500 Ma, suggesting activity at PM until this time.