Variable Resolution Bathymetry and Geomorphology of Tamu Massif



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Tamu Massif is currently the world’s largest known volcano covering ~315,000 km2 in area. It is located off the coast of Japan in the Pacific Ocean and represents the oldest and largest edifice of the Shatsky Rise oceanic plateau. New multibeam echosounder (MBES) data were combined with legacy MBES, single beam echosounder (SBES), and satellite altimetry (SA) data to compile a bathymetric map of Tamu Massif. Approximately 130 million depth soundings and estimates were combined into a variable resolution grid through stacking of data sets. New observations from these data include the discovery of a Y-shaped ridge that is interpreted as a relict triple junction that formed as the result of a ridge jump. Evidence of spreading ridges and chains of secondary cones parallel to magnetic lineations help explain Tamu Massif’s elongate shape in a NE-SW orientation. Escarpments are identified and correlated with known faults and occur primarily in two orientations. Escarpments trend perpendicular to flank slopes at ~5000 m and are observed on all sides of Tamu Massif except the north. These escarpments are interpreted as the result of differential subsidence. Other escarpments have orientations parallel to magnetic lineations formed at spreading ridges and are likely a result of ridge faulting. Mass wasting is observed in the form of erosional channels, a submarine slide, sediment slumping, and sediment creep. These features are interpreted as the result of gravitational loading and sediment instability. Moats around secondary cones, ripples on the summit sediment cap, and channel features are probably the result of bottom currents.



Tamu Massif, Shatsky Rise, Geomorphology, Bathymetry, Variable Resolution Bathymetry, Triple Junction