Lava morphology mapping by expert system classification of high-resolution side-scan sonar imagery from the East Pacific Rise, 9°-10°N

Fine-scale lava morphology has been classified on the ridge crest of the East Pacific Rise between 9 degrees 15'N and 10 degrees 02'N using an expert system classification method. This method establishes the means to classify complicated seafloor environments by integrating textural and geometric feature attributes from a high-resolution side-scan sonar dataset where ground-reference data are available from near-bottom visual observations. The classification in this study focuses upon mapping the lava morphology distribution of sheet, lobate, and pillow flows along the East Pacific Rise. The reliability of the classification has been evaluated using an accuracy assessment. The study region yields a coverage area of 37,814 m(2) (44%) for lobate flows; 10,421 m(2) (12%) for pillow flows; 15,096 m(2) (18%) for sheet flows; 19,679 m(2) (23%) for fissured areas; and 2,967 m(2) (3%) for shadows or no data. The systematic distribution of lava morphology along the ridge found in this study supports the idea of using the regional distribution of surface morphology as an indicator of emplacement dynamics and supports an organization of the volcanic plumbing system at a third order segmentation scale beneath mid-ocean ridges.