Ancestral submarine growth of kïlauea volcano and instability of its south flank

摘要: Joint Japan-USA cruises in 1998-99 explored and sampled the previously unstudied deep offshore region south of Kilauea. Bathymetric features, dive observations, recovered samples indicate that 3-km-deep mid-slope bench, bounded seaward by a 2-km-high lower scarp, is underlain massive turbidite sandstone interbedded debris-flow breccia. Debris-flow clasts are submarine-erupted (high-S) alkalic basalt, distinctive fine- to coarse-grained gabbro nephelinite (some containing phlogopite), subordinate transitional basalt. No similar recent Kilauea tholeiite. Primary volcanic deposits (pillow hyaloclastite breccia) absent. The breccia matrix, large fraction volcaniclastic apron, mainly subaerially erupted (low-S) tholeiitic glass sand generated shoreline processes on pre-Kilauea volcanoes. Fractures, shears, slickensided clasts, open folds widespread deformation low scarp; upward-decreasing proportions materials define gross stratigraphy. Alkalic high-S compositions many basalt some derivation from submarine Lo'ihi stage ancestral Kilauea, prior growth its shield. Slopes (3300-2800 m depth) above bench contain (S >750 ppm) pillow lava defining initial flank subalkaline geometry diverse constituents scarp require landsliding during volcanism at 200-300 ka, shield inception Hilina faults. active slump structures Kilauea's an early stage, thus possibly posing greater potential for future large-scale tsunamis.