Analysis of hydrologic structures within Mauna Kea volcano using diamond wireline core drilling

Author:

Thomas, D. M., Haskins, E.

Title:

Analysis of hydrologic structures within Mauna Kea volcano using diamond wireline core drilling

Periodical:

AGU Fall Meeting Abstracts

Year:

2013

Volume:

11

Subject:

Humuula Groundwater Research Project Hydrology Mauna Kea

Summary:

The Humu'ula Groundwater Research Project was undertaken on the Island of Hawaii in an effort to characterize the hydrologic structures controlling groundwater movement and storage within the dry (~430 mm/year annual rainfall) saddle region between Mauna Loa and Mauna Kea volcanoes. The project drilled a 1764 m, continuously-cored, borehole from an elevation of 1946 m amsl. Hydrologic conditions were strikingly different from those predicted by conventional models for ocean islands: the formation was dry down to only ~150 m where the first, thin, perched aquifer was encountered; a second, more substantial, perched aquifer was reached at only ~220 m depth that extended to ~360 m where a sequence of (remarkably thin) perching formations were recovered in the core down to about 420 m where unsaturated rocks were again encountered. Saturated conditions resumed at 550 m depth that continued to the total depth drilled; this latter zone is inferred to be the basal aquifer for Mauna Kea within this region of the island. Our initial analysis of the core suggests that thin, clay-rich, perching formations in the shallow stratigraphic column play a much larger role in groundwater transport than has generally been recognized; in the deeper interior of the volcano, compaction of flow boundaries (the major water carriers in the shallow stratigraphy) leads to a progressive decrease in permeability and reduction in the transport rates of recharge toward the shoreline aquifers.

Label:

Geology

URL:

http://adsabs.harvard.edu/abs/2013AGUFM.H11I1263T

Date:

December 1, 2013

Collection:

Periodicals