October 18, 1996

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.

Hawaii Scientific Drilling Project

Early last week, C. Barry Raleigh, Dean of the School of Ocean and Earth Science and Technology at the University of Hawaii, Manoa, announced that the National Science Foundation approved and funded the Hawaii Scientific Drilling Project (HSDP) proposal. The main objective of the project is to obtain a complete stratigraphic section (sequence of rock units) of a "hot-spot" volcano to provide information on the evolution of the volcano through time. Because this information is not available from surface exposures, HSDP will drill and core a 15,000-foot deep hole into Mauna Kea Volcano.

The feasibility of this project was demonstrated by a 3,464-foot-deep "pilot hole" drilled near Keaukaha in 1993, when core samples were recovered for 90% of the hole. The upper 920 feet of the hole were comprised of lavas from Mauna Loa, and the lower 2,544 feet were Mauna Kea lavas. Ages of the core samples from the bottom of the hole were as old as 400,000 years before present.

Principal investigators for the project are from the University of California at Berkeley, the California Institute of Technology, and the University of Hawaii at Manoa. Scientists from the U.S. Geological Survey will collaborate with them in analyzing the drill cores and in the geophysical logging of the drill hole.

As the oceanic plate carries the volcano over the "hot spot," the evolution of the volcano is thought to reflect the structure and composition of the mantle "plume" that the volcano passes. One of the significant results of the "pilot hole" was from the radiogenic isotope and trace-element chemical analyses of the Mauna Kea lavas. They suggested that variations involve changes in melting conditions and not in compositional changes of the mantle source. The deeper drill hole will provide more information on this by covering a longer section across the mantle "plume."

The new drill hole is scheduled to start next year and will be located in the quarry near the airport. The project is to last for at least six years with three periods of drilling. Funding to the University of Hawaii is expected to be up to $8 million. Another $3 to $4 million in funding will go to the other institutions in support of research to be conducted on the core or in the drill hole. The majority of the UH funding will be spent on drilling activities and on post-drilling science.

As in drilling the "pilot hole," UH will provide students and recent geology graduates of UH-Hilo an opportunity to be involved in basic research as scientific support staff members. Local contractors will be favored for all on-site work.

Kilauea Eruption Status

The current eruptive activity of Kilauea Volcano continues unabated. Although the size of the steam plume at the coastal entry has diminished at times during the past two weeks, the volume of lava flowing through the tube system remains unchanged. The ocean entry of the lava has been tubed over, causing the production of steam to lessen.

Two earthquakes were felt in the last week. At 8:48 p.m. on October 15, residents of Glenwood and Volcano were shaken by a magnitude 3.0 temblor. The earthquake was located 12 miles southeast of the summit of Kilauea Volcano at a depth of nearly 5 miles. The following night, at 10:12 p.m., residents of Pahala felt an earthquake located 6 miles north of them at a depth of 7 miles. The temblor had a magnitude of 3.3.