HR: 0830h
AN: V21D-0547    [PDF]
TI: Morphologic Comparison of Submarine Lava Channels on the East Pacific Rise and Simulated Channel Flows
AU: * Garry, W B
EM: wbgarry@acsu.buffalo.edu
AF: University at Buffalo, Dept. of Geology 876 Natural Science Complex, Buffalo, NY 14260 United States
AU: Gregg, T K
EM: tgregg@nsm.buffalo.edu
AF: University at Buffalo, Dept. of Geology 876 Natural Science Complex, Buffalo, NY 14260 United States
AU: Schouten, H
EM: hschouten@whoi.edu
AF: WHOI, Dept. of Geology and Geophysics, Woods Hole, MA 02543 United States
AU: Tivey, M
EM: mtivey@whoi.edu
AF: WHOI, Dept. of Geology and Geophysics, Woods Hole, MA 02543 United States
AU: Fornari, D
EM: dfornari@whoi.edu
AF: WHOI, Dept. of Geology and Geophysics, Woods Hole, MA 02543 United States
AB: Submarine lava channels observed on the East Pacific Rise (EPR) between $9-10\deg$ N exhibit five prominent surface textures: lobate, jumbled, lineated, folded, and smooth. These textures are similar in appearance and distribution to final morphologies observed in polyethylene glycol (PEG ) channel flows produced in laboratory simulations. Maps of the surface textures for both submarine and simulated flows were made to compare the distribution of the various textural types. Photomosaics of tow-camera images taken near the axial summit collapse trough of the EPR were used to analyze the submarine lava channels. The mosaics are made from swaths of images that have a 6-m field of view, and cross channels that are as wide as 115 m. PEG channel flows were produced on slopes of $<$$10\deg$. The final flow morphologies formed by solidified PEG after extrusion had ceased were mapped and compared to the submarine cross-channel mosaics. Levees of both submarine and PEG channels are lobate. The outer margins of PEG levees are easy to see, but flow margins are not as obvious in the submarine images, making it difficult to determine submarine flow and levee widths. After effusion of PEG has ceased in simulated flows, the solidified crust on the wax within the channel subsides, leaving a high-standing levee and a low-lying channel crust. Similarly, images of the channel-levee margin in submarine flows show the crust in the channel at a lower level than the top of the levees, indicating subsidence of channel crust after the eruption had ceased. The channel-levee transitions in submarine flows are characterized by a zone of jumbled lava. Jumbled pieces of solidified PEG are not present at the channel-levee margin after drain-out, but a shear zone is observed at this location during emplacement. The observed jumbled region in submarine channels may be generated by a similar shear zone at the channel-levee margin, combined with pieces of crust broken during channel subsidence. Crust textures in submarine channels are various combinations of jumbled, lineated, and smooth, while PEG channel crusts are typically smooth or folded. Analysis of flow textures, as well as channel and levee dimensions in submarine flows, will contribute to a better understanding of the emplacement and evolution of lava flows at mid-ocean ridges.
UR: http://www.whoi.edu/atlantis74
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3035 Midocean ridge processes
DE: 3045 Seafloor morphology and bottom photography
DE: 8429 Lava rheology and morphology
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting