HR: 1340h
AN: P13A-1039    [Abstracts]
TI: Emplacement of Long Volcanic Features on the Moon: A Review of the Mare Imbrium Lava Flows and Vallis Schroteri
AU: * Garry, W B
EM: garryw@si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, PO Box 37012, MRC 315, Washington, DC 20013, United States
AU: Warner, N H
EM: Nicholas.Warner@asu.edu
AF: School of Earth and Space Exploration, Arizona State University, Box 871404, Tempe, AZ 85287, United States
AU: Zimbelman, J R
EM: Zimbelmanj@si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, PO Box 37012, MRC 315, Washington, DC 20013, United States
AB: Two of the longest and best preserved individual volcanic flow features on the Moon are the lava flows in Mare Imbrium and the rille, Vallis Schroteri, on Aristarchus Plateau. The Mare Imbrium lava flows are defined by flow margins and leveed channels, whereas Vallis Schroteri is a lunar sinuous rille, carved into the plateau without defined flow margins. Both features were heavily researched in the 1970's using Lunar Orbiter and Apollo images, as well as radar and telescopic observations with later studies incorporating Clementine data. The Mare Imbrium lava flows are the most widely studied lunar flows because of the well-defined flow margins and traceability of the flows from the source region to the flow front. The flows extend for 1200 km from the source near Euler crater, covering an area of 2.0 x 10⁵ km² with an estimated eruptive volume of 4 x 10⁴ km³. Flow margins are 10 - 65 m thick and leveed channels are 0.4 - 2.0 km wide and 40 - 70 m deep. Previous research has interpreted the Mare Imbrium flows to have been emplaced in three phases (Phase I, II, and III) over a period of 0.5 billion years (3.0 - 2.0 Ga). Effusion rates of 8.2 x 10⁴ to 2.5 x 10⁵ m³/s and channel velocities of 0.5 - 1.4 m/s have been calculated for Phase III, but the emplacement of Phase I or II flows have not been addressed. Vallis Schroteri, the largest rille on the lunar surface, extends for 125 km, with an average depth of 380 m and an average width of 4.4 km. Reoccupation of the primary rille and evidence of thermal erosion are exhibited by a secondary rille that meanders through the floor of the rille and cuts through the distal wall, extending for another 40 km. Multi-spectral analysis of Vallis Schroteri reveals basaltic-composition rock exposed in the rille walls. The rille extends into Oceanus Procellarum, but there is no obvious evidence of lava flow margins that can be traced back to the mouth of the rille. We interpret Vallis Schroteri to have formed by thermal erosion of underlying anorthosite, basalt, and/or regolith by turbulent flow of basaltic material with effusion rates of 10³ to 10⁶ m³/s over a period of 10 to 100 years. Interpretation of the two volcanic features provides important constraints on eruption parameters for lava flows and sinuous rilles on the Moon.
DE: 6063 Volcanism (5480, 8450)
DE: 6250 Moon (1221)
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting