[USDP] USDP - Unzen Scientific Drilling Project

Climate & Ecosystems

Year of Application: 2001

Expedition ID: 5010

Current Status: completed

active volcano
directional drilling
explosion hazards
thermal regimes
volcanic systems
Master Data

Prof. Dr. Francois Holtz (PI)
Dr. Kai-Uwe Hess (PI)
Prof. Dr. Harald Behrens (PI)
Dr. Stefan Dultz (PI)
Dr. Martin Zimmer (PI)
Prof. Dr. Joerg Erzinger (PI)
Prof. Dr. Helga de Wall (PI)
Prof. Dr. Jens Fiebig (PI)
Prof. Dr. Donald Bruce Dingwell (PI)
Dr. Burkhard Schillinger (PI)

Dr. Benoit Cordonnier (Scientific Participant)
Dr. Tim Yilmaz (Scientific Participant)
Dr. Sarah B. Cichy (Scientific Participant)
Dr. Jeremie Vasseur (Scientific Participant)
Prof. Dr. Roman Botcharnikov (Scientific Participant)

Projektstart: 17 February, 2003
Projektdauer: 12
Geologisches Alter:

Latitude: 32°46'11''N


Regionen & Städte:

Nagasaki Province
Shimabara Peninsula
Unzen Volcano

Longitude: 130°17'11''E



hard rock

Drilling Data

Drilling Depth: 1812.0
Core Yield: 51.7
Core Length: 56.1
Amount of Drill Holes: 4
Amount of Drill Locations: 1

Core Length-Drill Depth-Ratio: 2.85
Core Yield-Core Length-Ratio: 92.16

Related DFG-Projects

[Behrens] Carbonation of porous rocks by interaction with magmatic and hydrothermal fluids - a case study on Unzen volcano, Japan (2009 - 2015)

[Hess] 2D and 3D fabric quantification of conduit textures to understand eruption dynamics and mechanisms: unique in situ example of Mt Unzen (2016 - 2020)

[Hess] Development of an ultra-high resolution neutron computed tomography system for the characterisation of drill cores. (2009 - 2011)

[Holtz] Experimental study on vesiculation and formation of groundmass microlites induced by decompression: Constraints on processes related to magma ascent at Unzen volcano (2007 - 2011)

[Hess] Viscous flow of magmas from Unzen volcano, Japan - Implications for magma ascent and emplacement (2005 - 2009)

[Holtz] Pre-eruptive conditions prior to and after magma mixing at Unzen volcano: constraints from high pressure experimental investigations (2004 - 2008)

[Behrens] Carbonation of porous rocks by interaction with magmatic and hydrothermal fluids - a case study on Unzen volcano, Japan (2011 - 2015)

[Behrens] Viscous flow of magmas from Unzen volcano, Japan - implications for magma mixing and ascent (2002 - 2008)

[Dingwell] Das explosive Verhalten des Fugendake, Kyushu, Japan: Charakterisierung der eruptiven Produkte und Identifizierung der Eruptionsmechanismen im Vorfeld und in Begleitung des Unzen Scientific Drilling Project (USDP) (2001 - 2003)

[Zimmer] On the geochemistry of volcanic gases and fluids from the Unzen volcano - ICDP-Unzen-Conduit-Drilling (2002 - 2005)

[Holtz] Distribution of H20, CO2, S and Cl between silicate melts, gas phase and minerals on the example of the Unzen volcano: application for degassing processes (2001 - 2005)

[Dingwell] Rheologische und mechanische Charakterisierung der Dom-Laven des Vulkans Unzen in Vorbereitung auf das ICDP-Bohrprojekt Unzen (1997 - 2002)

[Holtz] Experimentelle Untersuchungen über die Wechselwirkungen zwischen C-H-O-S Fluiden und Magmen (1997 - 2002)


Volcanic eruptions of felsic magma cause large disasters. More than 50 % of the recent disasters are due to events related to mass flows, such as pyroclastic/debris flows, debris avalanches and tsunamis, the latter resulting from entry of mass flows into the sea or lakes. In more explosive events, volcanic ash and gas cause other serious problems, such as global-scale environmental change and failure of jet engines of airplanes flying over the volcanoes. Although all these events are destructive, they are destructive in different ways. Thus it is vitally important to understand not just when a volcano will erupt, but how it will erupt. Felsic volcanoes are abundant in island arcs and continental margins, where cities with large populations are concentrated. Unzen Volcano is such a volcano, where a huge volcanic disaster occurred about 200 years ago and the latest eruption occurred in 1990-95. During the latter period, about ten thousand pyroclastic flows were produced due to partial collapses of a growing lava dome, threatening the lives of people around the volcano. Eruptions of felsic magmas are not always explosive. Three major recent eruptions, Pinatubo in 1991, Mount St. Helens in 1980, and Unzen in 1990-95, were caused by felsic magmas with chemical compositions similar to each other, including similar concentrations of the volatile components that account for explosive activity. However, styles of eruption among the three are very different. Nearly all of Pinatubo’s magma was ejected explosively as ash falls and pyroclastic flows. Mount St. Helens’ eruptions began explosively, but produced more and more dome lavas as the episode progressed. Unzen was least explosive, with almost no ash eruptions and with nearly all pyroclastic flows being due to disintegration upon collapse of already extruded lava, not to fragmentation within the conduit. Evidently, a degassing process where the volatile component escapes effectively from magma during its ascent is the major factor controlling whether volcanism is explosive or non-explosive, and hence the kind of damage that an eruption will produce. The upper part of the magmatic conduit is believed to be the place where most degassing occurs, based upon what is known about the pressure-dependent solubility of volatiles in magma and on the source location of geophysical signals during eruption. Such signals as volcanic tremor may be direct evidence of the degassing process. However, there is much to learn about how so much gas can escape from magma so rapidly. In-situ inspection of the conduit and its wall rock is the most effective approach to understand the mechanism. Scientific drilling at Inyo Domes, at Long Valley Caldera, is the only case to date where a young volcanic conduit was penetrated and sampled, but the 600-year-age of eruption was too old for there to be complementary geophysical monitoring data and the conduit had cooled completely. Despite these limitations, an important model of degassing was proposed, based on the results. The results have been extended by examination of geologic exposures of roots of old lava domes such as Mule Creek Dome in New Mexico, which revealed structures similar to those found in drilling, and by development of numerical models for degassing. A necessary next step in developing our understanding of the causes of explosive versus non-explosive eruption is to drill into a conduit whose eruptive activity was actually observed. Drilling into the conduit of the latest lava dome at Unzen is a most desirable goal, because the lava that solidified in the conduit is still hot and the location of conduit is well defined by geophysical signals recorded intensively and precisely during eruption. With this challenging scientific project, the combination of direct information on degassing obtained by drilling with geophysical signals obtained during the eruption can solve the problem of eruption mechanisms of felsic magma. In addition, the meanings of geophysical signals can be more correctly interpreted for predicting eruptions and the development of hydrothermal systems after eruption can be elucidated. Two pre-proposals of Unzen scientific drilling were evaluated by the International Continental Scientific Drilling Program (ICDP). The importance of scientific drilling and the technical problems of drilling itself were discussed in international workshops in 1997 and 2000. Following the first meeting, the Science and Technology Agency of Japan initiated funding of the Unzen Scientific Drilling Project (USDP), as a one-year feasibility study. During the next three years, drilling of two flank holes and one pilot hole for the conduit drilling were completed or are in progress. Questions of the tectonic and magmatic development history of Unzen are being solved through synthesis of geologic data from the surface and the flank holes, and design of the conduit drilling and selection of the drill site has been undertaken. Slant drilling from the northern upper slope of the volcano was found to be an option able to penetrate the conduit above sea level. The permitting process is easier in this site and the cost of drilling is less expensive than a site proposed initially that is within a special area of nature preservation, close to the dome. It is proposed that conduit drilling will start in 2002 jointly with STA and ICDP, and continue until 2005. Japanese principal investigators are asking STA to defray the major portion of the conduit drilling cost, estimated to be 8.8 MD in total. Fund for a portion of drilling operation (total 3 MD) is requested from ICDP. Foreign scientists, including Co-investigators, will request their own research resources from their respective national science foundations. Five principal investigators have the responsibility of science handling of the conduit drilling, including samples description-partition and logging experiments. Over 60 scientists comprise an international team of the conduit drilling project at Unzen.

Related Publications

Yilmaz, Tim I, Wadsworth, Fabian B, Gilg, H Albert, Hess, Kai-Uwe, Kendrick, Jackie E, Wallace, Paul A, Lavallée, Yan, Utley, James, Vasseur, Jérémie, Nakada, Setsuya (2021). "Rapid alteration of fractured volcanic conduits beneath Mt Unzen" Bulletin of Volcanology p1-14

Lavallée, Yan, Miwa, Takahiro, Ashworth, James D, Wallace, Paul A, Kendrick, Jackie E, Coats, Rebecca, Lamur, Anthony, Hornby, Adrian, Hess, Kai-Uwe, Matsushima, Takeshi (2021). "Transient conduit permeability controlled by a shift between compactant shear and dilatant rupture at Unzen volcano (Japan)" Solid Earth Discussions p1-39

Friese, Karl-Ingo, Cichy, Sarah B., Wolter, Franz-Erich, Botcharnikov, Roman E. (2013). "Analysis of tomographic mineralogical data using YaDiV—Overview and practical case study" Computers & Geosciences 9 p92-103

Lavallée, Yan, Benson, Philip M, Heap, Michael J, Hess, Kai-Uwe, Flaws, Asher, Schillinger, Burkhard, Meredith, Philip G, Dingwell, Donald B (2013). "Reconstructing magma failure and the degassing network of dome-building eruptions" Geology 41 p515-518

Benson, Philip M., Heap, Michael J., Lavallée, Yan, Flaws, Asher, Hess, K. U., Selvadurai, A. P. S., Dingwell, Donald B., Schillinger, B. (2012). "Laboratory simulations of tensile fracture development in a volcanic conduit via cyclic magma pressurisation" Earth and Planetary Science Letters p231-239

Perugini, D., De Campos, C. P., Ertel-Ingrisch, W., Dingwell, D. B. (2012). "The space and time complexity of chaotic mixing of silicate melts: Implications for igneous petrology" Lithos 155 p326-340

Cordonnier, B., Schmalholz, S. M., Hess, K. U., Dingwell, D. B. (2012). "Viscous heating in silicate melts: An experimental and numerical comparison" Journal of Geophysical Research: Solid Earth 117 pn/a-n/a

Lavallée, Y., Benson, P. M., Heap, M. J., Flaws, A., Hess, K.-U., Dingwell, D. B. (2012). "Volcanic conduit failure as a trigger to magma fragmentation" Bulletin of Volcanology 74 p11-13

Hess, K.-U., Flaws, A., Mühlbauer, M.J., Schillinger, B., Franz, A., Schulz, M., Calzada, E., Dingwell, D.B., Bente, K. (2011). "Advances in high-resolution neutron computed tomography: Adapted to the earth sciences" Geosphere 7 p1294-1302

Cichy, Sarah Bettina (2011). "Experimental study on vesiculation and formation of groundmass microlites induced by decompression: constraints on processes related to magma ascent at Unzen volcano" Dissertation p175

Cichy, Sarah B., Botcharnikov, Roman E., Holtz, François, Behrens, Harald (2011). "Vesiculation and Microlite Crystallization Induced by Decompression: a Case Study of the 1991–1995 Mt Unzen Eruption (Japan)" Journal of Petrology 52 p1469-1492

Vetere, Francesco, Behrens, Harald, Holtz, Francois, Vilardo, Giuseppe, Ventura, Guido (2010). "Viscosity of crystal-bearing melts and its implication for magma ascent" Journal of Mineralogical and Petrological Sciences 105 p151-163

Cordonnier, Benoit (2009). "Non-Newtonian effects in silicate liquids and crystal bearing melts: Implication for magma dynamics" Dissertation p144

Cordonnier, B., Hess, K. U., Lavallee, Y., Dingwell, D. B. (2009). "Rheological properties of dome lavas: Case study of Unzen volcano" Earth and Planetary Science Letters 279 p263-272

Behrens, Harald, Hahn, Matthias (2009). "Trace element diffusion and viscous flow in potassium-rich trachytic and phonolitic melts" Chemical Geology 259 p63-77

Koyaguchi, Takehiro, Scheu, Bettina, Mitani, Noriko K., Melnik, Oleg (2008). "A fragmentation criterion for highly viscous bubbly magmas estimated from shock tube experiments" Journal of Volcanology and Geothermal Research 178 p58-71

Scheu, Bettina, Kueppers, Ulrich, Mueller, Sebastian, Spieler, Oliver, Dingwell, Donald B. (2008). "Experimental volcanology on eruptive products of Unzen volcano" Journal of Volcanology and Geothermal Research 175 p110-119

Mueller, Sebastian, Scheu, Bettina, Spieler, Oliver, Dingwell, Donald B (2008). "Permeability control on magma fragmentation" Geology 36 (5) p399-402

Tretner, Andreas, Zimmer, Martin, Erzinger, Jörg, Nakada, Setsuya, Saito, Masaki (2008). "Real-time drill mud gas logging at the USDP-4 drilling, Unzen volcano, Japan" Journal of Volcanology and Geothermal Research 175 p28-34

Lavallee, Y., Meredith, P. G., Dingwell, D. B., Hess, K. U., Wassermann, J., Cordonnier, B., Gerik, A., Kruhl, J. H. (2008). "Seismogenic lavas and explosive eruption forecasting" Nature 453 p507-510

Botcharnikov, Roman E., Holtz, Francois, Almeev, Renat R., Sato, Hiroaki, Behrens, Harald (2008). "Storage conditions and evolution of andesitic magma prior to the 1991–95 eruption of Unzen volcano: Constraints from natural samples and phase equilibria experiments" Journal of Volcanology and Geothermal Research 175 p168-180

Vetere, Francesco, Behrens, Harald, Schuessler, Jan A., Holtz, Francois, Misiti, Valeria, Borchers, L. (2008). "Viscosity of andesite melts and its implication for magma mixing prior to Unzen 1991–1995 eruption" Journal of Volcanology and Geothermal Research 275 p208-217

K.-U. Hess, B. Cordonnier, Y. Lavallée, D. B. Dingwell (2007). "High-load, high-temperature deformation apparatus for synthetic and natural silicate melts" Review of Scientific Instruments 78 p075102

Lavallée, Yan, Hess, Kai-Uwe, Cordonnier, Benoit, Dingwell, Donald Bruce (2007). "Non-Newtonian rheological law for highly crystalline dome lavas" Geology 35 (9) p843-846

Botcharnikov, Roman E, Holtz, Francois, Behrens, Harald (2007). "The effect of CO2 on the solubility of H2O-Cl fluids in andesitic melt" European Journal of Mineralogy 19 p671-680

Scheu, Bettina, Spieler, Oliver, Dingwell, Donald B. (2006). "Dynamics of explosive volcanism at Unzen volcano: an experimental contribution" Bulletin of Volcanology 69 p175-187

Taddeucci, J., Spieler, O., Ichihara, M., Dingwell, D. B., Scarlato, P. (2006). "Flow and fracturing of viscoelastic media under diffusion-driven bubble growth: An analogue experiment for eruptive volcanic conduits" Earth and Planetary Science Letters 243 p771-785

Kueppers, Ulrich, Scheu, Bettina, Spieler, Oliver, Dingwell, Donald B. (2006). "Fragmentation efficiency of explosive volcanic eruptions: A study of experimentally generated pyroclasts" Journal of Volcanology and Geothermal Research 153 p125-135

Botcharnikov, R. E., Behrens, H., Holtz, F. (2006). "Solubility and speciation of C–O–H fluids in andesitic melt at T = 1100–1300 °C and P = 200 and 500 MPa" Chemical Geology 229 p125-143

Scheu, B., Kern, H., Spieler, O., Dingwell, D. B. (2006). "Temperature dependence of elastic P- and S-wave velocities in porous Mt. Unzen dacite" Journal of Volcanology and Geothermal Research 153 p136-147

Kueppers, Ulrich, Perugini, Diego, Dingwell, Donald B. (2006). "“Explosive energy” during volcanic eruptions from fractal analysis of pyroclasts" Earth and Planetary Science Letters 248 p800-807

Sato, Hiroaki, Holtz, Francois, Behrens, Harald, Botcharnikov, Roman, Nakada, Setsuya (2005). "Experimental Petrology of the 1991–1995 Unzen Dacite, Japan. Part II: Cl/OH Partitioning between Hornblende and Melt and its Implications for the Origin of Oscillatory Zoning of Hornblende Phenocrysts" Journal of Petrology 46 (2) p339-354

Holtz, Francois, Sato, Hiroaki, Lewis, Jared, Behrens, Harald, Nakada, Setsuya (2005). "Experimental petrology of the 1991–1995 Unzen dacite, Japan. Part I: phase relations, phase composition and pre-eruptive conditions" Journal of Petrology 46 (2) p319-337

Behrens, Harald, Ohlhorst, Susanne, Holtz, Francois, Champenois, Michel (2004). "CO2 solubility in dacitic melts equilibrated with H2O-CO2 fluids: Implications for modeling the solubility of CO2 in silicic melts" Geochimica et Cosmochimica Acta 68 (22) p4687-4703

Ui, Tadahide, Matsuwo, Norimichi, Sumita, Mari, Fujinawa, Akihiko (1999). "Generation of block and ash flows during the 1990–1995 eruption of Unzen Volcano, Japan" Journal of Volcanology and Geothermal Research 89 p123-137

Jousset, Philippe, Okada, Hiromu (1999). "Post-eruptive volcanic dome evolution as revealed by deformation and microgravity observations at Usu volcano (Hokkaido, Japan)" Journal of Volcanology and Geothermal Research 89 p255-273