Hawaiian volcanoes are the most comprehensively

studied on Earth. Nevertheless, most

of the eruptive history of each one is inaccessible

because it is buried by younger lava

flows or is exposed only below sea level. For

those parts of Hawaiian volcanoes above sea

level, erosion typically exposes only a few

hundred meters of buried lavas (out of a total

thickness of up to 10 km or more).Available

samples of submarine lavas extend the time

intervals of individual volcanoes that can be

studied. However, the histories of individual

Hawaiian volcanoes during most of their ~1-million-year passages across the zone of melt

production are largely unknown

DePaolo, Donald J.

Stolper, Edward

Thomas, Donald M.

English

Scientists recently drilled through a Hawaiian volcano to a depth of 3,098 meters below sea level

Caltech Authors - Main

VOLCANOLOGY 
Deep Drilling into a Hawaiian Volcano 
Scientists recently drilled through a Hawaiian volcano to a depth of 3,098 meters below sea level. 
by Donald J. DePaolo, Department of Geology and Geophysics, University of California-
Berkeley, Berkeley, USA; Edward Stolper, Division of Geological and Planetary Sciences, 
California Institute of Technology, Pasadena, USA; and Donald M. Thomas, Hawaii Institute 
of Geophysics and Planetology, University of Hawaii, Honolulu, USA 
Hawaiian volcanoes are the most comprehensively 
studied on Earth due, in part, to their active volcan-
ism, their accessibility and location within the United 
States, and their excellent exposure. Nevertheless, 
most of the eruptive history of each of the five volca-
noes exposed on the island of Hawaii is inaccessible 
because it is buried by younger lava flows or exposed 
only below sea level. For those parts of Hawaiian vol-
canoes above sea level, erosion typically exposes only 
a few hundred meters of buried lavas (out of a total 
thickness of up to 10 kilometers or more). Available 
samples of submarine lavas extend the time intervals 
of individual volcanoes that can be studied. However, 
the histories of individual Hawaiian volcanoes during 
most of their 1-million-year passages across the zone 
of melt production are largely unknown. 
If stratigraphic sequences of lava flows from 
Hawaiian or other oceanic volcanoes spanning long 
time periods could be obtained, they would provide 
valuable probes of plume structure and magmatic 
processes. Continuous core drilling through lava 
sequences on the flanks of oceanic volcanoes is the 
only way to sample lava flows that span the entire 
eruptive history of a volcano. Imagine the idealized 
growth of a volcano as one lava flow, then another on 
top of it, and so on; obviously, the older flows are 
buried by the younger ones and hidden from view, 
but if we could start at the top and drill all the way to 
the bottom, we would sample all the lava flows in 
reverse order. Although real volcanoes are more com-
plex than a simple layer cake, this helps to illustrate 
the concept behind the drilling project. 
The opportunity to probe the long-term history of 
a Hawaiian volcano by drilling has led an interna-
tional group of scientists to core-drill into Mauna Kea 
volcano on the island of Hawaii. Planning for the 
Hawaii Scientific Drilling Project (HSDP) began in 
1986. The objective of the HSDP is to recover and 
characterize as nearly a continuous sequence of core 
samples as possible to a depth of at least 4.5 kilometers. 
In the fall of 1993, the National Science Foundation 
(NSF) supported the core-drilling of a 1.06-kilometer-
deep "pilot hole" through a veneer of Mauna Loa 
flows into the flank of Mauna Kea volcano in Hilo, 
Hawaii (see map on page 12). About 90%, of the core 
was recovered, yielding a long record of fresh subaer-
ial lavas extending back 400 thousand years. 
Petrological, geochemical, geomagnetic, and vol-
canological characterization of the recovered core, 
downhole logging, and fluid sampling provided a 
view of the evolution and internal structure of a major 
oceanic volcano that was unavailable from surface 
exposures. Detailed information on the pilot hole can be 
found at the HSDP Web site (http: I I expet.gps.caltech. 
eduiHawaii_project.html) and in the May 1996 spe-
cial issue of AGU's JGR. Based on the success of the 
pilot drill hole, the first of two phases of deep drilling 
began in Hilo on March 15, 1999, at a site 2 kilometers 
south of the pilot hole. Supported primarily by the 
NSF, but with significant support from the 
International Continental Drilling Program in 
Potsdam, Germany, this first phase of deep drilling 
was completed on September 23, 1999, at a depth of 
3,098 meters below sea level (mbsl). 
Site Selection, Drilling, 
Downhole Logging 
An abandoned quarry on the grounds of the Hilo 
International Airport was chosen as the site for the 
drill hole (see map on page 12). As was the case for 
the pilot hole, the site was chosen to be far from vol-
canic rift zones, so as to minimize chances of 
encountering intrusives, alteration, and high-tem-
perature fluids; to be close to the coastline, so as to 
minimize the thickness of subaerial lavas that 
would need to be penetrated to reach the older, sub-
marine parts of the Mauna Kea section; and in an 
industrial area, to minimize environmental and 
community impacts. 
Earth in Space, Vol. 13, No. 9, pp. 1-16 11 
~Okm 
"Kea" trend 
oihi 
"Loa" trend 
Panaewa flow 
5km 
Location map for the Hawaii Scientific Drilling Project pilot hole (drilled in 1993) and the first 
phase of deeper drilling (1 999). 
Although the Mauna Kea section was the primary 
target, this choice of site required drilling through a 
veneer of Mauna Loa flows, thereby providing addi-
tional information on the Mauna Loa volcanic succes-
sion as a complement to the coverage of the Mauna 
Kea sequence. 
Drilling into the volcano is not as difficult-or as 
dangerous-as it might sound. For one thing, the vol-
cano is no longer active, so there is very little chance 
of encountering hot magma. Also, the choice of the 
drilling site purposely avoided any areas where water 
has been heated up by nearby magma bodies. The 
most difficult parts of this drilling project turned out 
to be coring through highly fractured rocks and 
controlling water flows out of the drill hole from high-
pressure underground aquifers. 
Stratigraphy Interpretation 
in Terms of Evolution 
An integrated program of determinations of ages, 
chemical and isotopic compositions, magnetic and 
12 Earth in Space, Vol. 13, No. 9, pp. 1-16 
Series of illustrations demonstrating the progressive evolution 
of a Hawaiian volcano and showing the expected sequence of 
deposits with depth in the hole: (a) submarine/seamount phase 
(e.g., Loihl) showing the possibility of submarine landslides; (b) 
an emergent volcano, showing the eruption of subaerial lavas and 
the formation of hyaloc/astites by slumping of near-shore volcani-
clastic sediments; (c) main stage of shield building (e.g., Kilauea), 
illustrating major landslides, the formation of "massive" submarine 
units as tube-fed flows extending from subaerial to submarine 
conditions, the eruption of pillow lavas through the submarine 
flanks of the volcano, and shallow intrusives into the volcano 
flanks, including feeders for submarine flank eruptions; (d) after 
the end of shield-building (e.g., Mauna Kea), showing the near-
shore location of the HSDP drill hole. 
physical properties, and petrography of the recovered 
samples is underway and will continue over the next 
year. Our expectation is that the data will contribute to 
understanding mantle plumes, the internal structure 
and evolution of a major oceanic volcano, and related 
magmatic and volcanic processes. However, even in 
advance of the detailed characterization of the core 
that these studies will provide, the onsite characteri-
zation of the stratigraphic column and the preliminary 
geochemical data that are available provide insights 
into the internal structure and evolution of a 
Hawaiian volcano. 
The idealized stratigraphic sequence expected at a 
near-shore site such as Hilo, which is located 17 kilo-
meters south of the east rift of Mauna Kea, can be 
understood with the progression in the growth of a 
Hawaiian volcano as illustrated in the figure above. 
Although the overall stratigraphic section encoun-
tered during drilling is similar to that anticipated from 
the simple sequence shown in the figure above, it dif-
fers from it in several respects: 
• The transition from pillow lavas to debris flows 
might be expected based on the figure above to be 
abrupt, reflecting the unidirectional outward growth 
of the volcano, yet the actual section has these two 
rock types interfingered over a depth interval of at 
least 1 kilometer. Although it is not surprising that the 
transition from pillows to debris is not in fact sharp, 
the broad transition observed was not anticipated. 
• Pillow lavas were encountered in the section at a 
depth much shallower than expected. Based on the 
simple model illustrated in the figure, pillow lavas 
would not be expected shallower than 4-5.5 kilome-
ters below sea level in the core; yet they first appear at 
a depth of 2 kilometers below sea level. 
There are several possible explanations for the 
shallow occurrence of pillow lavas in the core, includ-
ing the following. First, at the phase of its growth that 
controlled the stratigraphy of the drill site, the east 
rift of Mauna Kea could have had a shallow slope of 
3-4°. Although this is not the norm, some Hawaiian 
rifts have slopes that are this shallow, so this cannot 
be ruled out. Second, the east rift of Mauna Kea may 
not always have been in its current location. For 
example, if it was initially further south, closer to the 
drilling site in Hilo, this could explain the shallower 
occurrence of pillows, and a complex interfingering 
of pillows and debris might accompany an evolving 
position of the rift relative to the drill site during 
movement of the rift toward its current location. 
Third, eruption of magma through the debris draping 
the submarine flanks of Mauna Kea's east rift could 
have produced abundant, undegassed pillow lava 
much higher up in the section than would be predict-
ed from the simple model of Hawaiian volcano 
growth illustrated in the figure. Support for this expla-
nation comes from studies showing that submarine 
Hawaiian eruptions are not confined to rift zones. 
• The "massive" basalts that make up 10% of the 
upper kilometers of the submarine section are not 
well understood. We have tentatively identified 
them as subaerial flows that continued past the 
shoreline and flowed substantial distances in lava 
tubes ( -4 km given their depths and assuming a 
submarine slope of 10°). Such flows do occur in 
younger Hawaiian submarine sections and are 
shown as an illustration in panel c. However, the 
absence of pillow structures associated with these 
units and the rarity of such flows on modern-day 
Hawaii are problematic. 
• The presence of intrusives at relatively shallow 
depths in the core was not expected, given the dis-
tance from the summit and the east rift of Mauna 
Kea. These units could be feeders for off-rift erup-
tions, or they could be evidence that Mauna Kea's 
east rift was previously further south than its cur-
rent location. 
Earth in Space, Vol. 13, No.9, pp. 1-16 13 
How Deep Can We Drill? 
The current schedule calls for remobilization of 
drilling equipment to the site during the last quarter 
of 2001 to re-enter the hole and continue the drilling 
program. 
The 1999 phase of the deep drilling effort was able 
to reach a depth that was nearly 650 meters deeper 
than originally envisioned for this phase. As a result, 
we will be able to start the next phase of drilling by 
opening the hole to a diameter of 15.9 centimeters to 
the current depth of 3.1 kilometers below sea level, 
and casing will be installed from the surface to that 
depth. From that depth, we will then core to a maxi-
mum depth determined by hole conditions and avail-
able funds. Based on the coring conditions encoun-
tered near the close of the 1999 phase of drilling, we 
have a target depth of 4.5 kilometers below sea level. 
However, the coring system is capable of a maximum 
depth of slightly more than 6.5 kilometers. If drilling 
A Few Words from the Authors 
Don DePaolo was born and raised in western New 
York state. He received a B.S. from the State 
University of New York at Binghamton in 1973 and a 
Ph.D. from the California Institute of Technology in 
1978. He was a professor at UCLA from 1978-1988 
and has been on the faculty at U.C. Berkeley since 
1988, where he teaches petrology and geochemistry. 
He is also a Senior Faculty Scientist at the E.O. 
Lawrence Berkeley National Laboratory. His research 
involves using mass spectrometry to study the geo-
chemistry of rocks and minerals, addressing such 
questions as the age and origin of igneous and meta-
morphic rocks, the evolution of the Earth's mantle, 
and the geochemistry of Earth's oceans in the geo-
logic past. He is currently on leave from Berkeley and 
doing research at the Australian National University 
as a John Simon Guggenheim fellow. 
Ed Stolper was born and raised in the Boston 
area. He received an A.B. from Harvard College in 
1974, an M.Phil. from the University of Edinburgh, 
Scotland, in 1976, and his Ph.D. from Harvard 
University in 1979. He joined the faculty at the 
California Institute of Technology in 1979 and has 
been there ever since. His research involves using 
experiments at high pressure and temperature, 
conditions and funding allow, this would enable us to 
approach and perhaps even penetrate the Cretaceous 
ocean floor beneath Mauna Kea. 
Source: Eos, March 27, 2001, p. 149. 
References 
Garcia, M. 0., and M. G. Davis, Submarine growth 
and internal structure of oceanic island volcanoes 
based on submarine observations of Mauna Loa vol-
cano, Hawaii, Geology, 29, pp. 163-166, 2001. 
Lockwood, J.P., and P. W. Lipman, Holocene eruptive 
history of Mauna Loa, USGS Prof. Pap., 1350, pp. 
509-535, U.S. Geological Survey, Washington, D.C., 1987. 
Moore, J. G., and W. W. Chadwick, Jr., Offshore 
geology of Mauna Loa and adjacent areas, Hawaii, in 
Mauna Loa Revealed: Structure, Composition, History, and 
Hazards, edited by J. M. Rhodes and J.P. Lockwood, 
pp. 21--44, American Geophysical Union, Washington, 
D.C., 1995. 
theory, and observation to understand the origin 
and evolution of igneous rocks on the Earth and 
other planets (including the Moon, Mars, and aster-
oids). He is currently chairman of the Division of 
Geological and Planetary Sciences at Caltech. 
Don Thomas got his B.S. in physics and chem-
istry from Dickinson College in Pennsylvania, an 
M.S. from Oregon Graduate Center, where he stud-
ied the surface chemistry of platinum, and a Ph.D. 
in chemistry from the University of Hawaii, where 
he began his fascination with volcanoes in a study 
of the chemical and isotopic compositions of the 
volcanic gases of Kilauea. Don is currently doing 
research to answer questions about how water 
moves through large oceanic volcanic structures 
and how it reacts with the volcanic rocks. He also 
works to understand mechanisms of volcanic erup-
tions, with the ultimate goal of predicting when 
eruptions might occur, and teaches classes for inter-
national students on techniques for monitoring 
active volcanoes. He is active in helping Hawaiian 
residents appreciate the wonders of the unique nat-
ural environment in which they live, while at the 
same time alerting them to the risks of living near 
active volcanoes. 
14 Earth in Space, Vol. 13, No.9, pp. 1-16 
