INTEGRATED GEOPHYSICAL AND DRILLING RESULTS FOR MAUNA KEA VOLCANO: HYDROLOGIC IMPLICATIONS

A suite of recent Magnetotelluric and Audio Magnetotelluric surveys conducted on Mauna Kea volcano has revealed evidence of multiple dike intrusions radiating out from the summit caldera. Some of these dikes appear to be associated with geologically recent eruptive events (as evidenced by thermal activity encountered by test bores), but some may be associated with earlier shield building and rift zone activity that has been now buried by post-shield eruptive products. The resistivity data acquired is also interpreted to suggest that water table elevations within the flanks of Mauna Kea are substantially higher than prior models of Hawaii’s hydrology have indicated. Test drilling, conducted in an effort to confirm the presence of high elevation groundwater has encountered high level groundwater, at elevations of more than 1500 m amsl within the south flank of Mauna Kea that is attributed to both perching formations, associated with variations in eruptive styles (e.g. effusive versus explosive) during Mauna Kea’s growth and evolution, as well as a broader dike impounded aquifer that may span the saddle region between Mauna Kea and Mauna Loa toward the south. Resistivity results now suggest that a similar system may be present on the north flank of Mauna Kea in the saddle between Mauna Kea and Kohala Volcano.

We will provide a summary of the recent geophysical survey results along with a revised conceptual model for groundwater storage and transport within Mauna Kea volcano.