FY 1995

Offshore geology of Mauna Loa and adjacent areas, Hawaii

Moore, J.G., and W.W. Chadwick, Jr.

Geophysical Monograph 92, 21–44, doi: 10.1029/GM092p0021, In Mauna Loa Revealed: Structure, Composition, History, and Hazards, J.M. Rhodes, and J.P. Lockwood (eds.), AGU, Washington, D.C. (1995)

Recent high-resolution multibeam sonar surveys of the seafloor near the island of Hawaii provide a new detailed view of the morphology and structure of the island's submarine flanks. We have merged this multibeam data with other digital topographic and bathymetric data from several sources to create a series of maps showing the topography, bathymetry, and overall morphology of the south part of the island of Hawaii (including all of Mauna Loa volcano) and an offshore region including the leading end of the Hawaiian Ridge from 20° to 18.5° north latitude. These morphologic maps cover an area of 167 km north-south (1.5° of latitude) by 277 km east-west (2.5° of longitude), with an area of ~46,000 km². The morphologic maps include a contoured bathymetric map, a slope map, and a shaded-relief map that show in previously unattained crispness the texture and detail of geologic features both above and below sea level. A geologic map was prepared of this subaerial and submarine area by making use of the morphologic detail of the maps coupled with previous subaerial and submarine geologic studies, including regional side looking sonar (GLORIA) surveys of the Hawaiian Exclusive Economic zone, surface ship dredging, coring, bottom photography, and submersible dives. This map outlines the areas covered by major rock units including terrestrial and subaqueous lava, fragmental quenched lava, submerged terrestrial lava, landslides, Cretaceous seamounts, and abyssal sediment. The map documents the importance of landslides, best exposed in the submarine realm, in the growth and decline of Mauna Loa and adjacent volcanoes.