Crater Eruption Research Articles

Origins and nature of large explosive eruptions in the lower East Rift Zone of Kīlauea volcano, Hawaii: Insights from ash characterization and geochemistry

Several powerful explosive eruptions have taken place in the populated lower East Rift Zone of Kīlauea within the past ∼750 years. These have created distinctive landforms, including a tephra rim enclosing Puʻulena Crater immediately south of the Puna Geothermal Venture power station, a tuff cone at Kapoho Crater near the eastern cape of the Island of Hawaiʻi, and a set of littoral cones, the Sand Hill in Nānāwale, where the 1840 lava flow poured into the ocean. Kapoho Crater tuff cone is the largest of these recent pyroclastic features. Mineral, glass, and melt inclusion analyses of tuff cone ash and later fissure-related scoriaceous materials also found within the crater indicate slightly evolved basaltic magmas (1120–1130 °C) that are compositionally similar to parts of the effusive lower East Rift Zone eruptions in 1955 and 2018. Tuff cone magmas were stored at depths of ∼2.5–3.5 km and had pre-eruptive volatile contents (0.5–0.8 wt% H2O, 280–340 ppm CO2, 1400–1800 ppm S) similar to other Kīlauea eruptions (e.g., 1959, 1960), suggesting that internal magma properties were unlikely to account for the unusual explosiveness of this eruption. Tephra componentry, grain-size analyses, and field observations confirm that the cone grew during a phreatomagmatic eruption mostly of vitric ash, probably where a fissure opened across the coastline or shallow ocean floor nearby. Supporting this hypothesis is the identification of at least two genera of marine diatoms within tuff cone strata. Sand Hill littoral cone ash is also vitric like that of Kapoho Crater, but distinctly coarser with abundant fluidal ejecta represented. In contrast, the Puʻulena Crater eruption deposited lithic ash and related blocks with minor juvenile magmatic contribution; a phreatomagmatic eruption that was dominantly phreatic. Differences in eruption styles are related to unique mechanics that tephra analyses help us interpret. While powerful explosive eruptions in the lower East Rift Zone are rare, they present a definite future hazard for inhabitants in this part of Hawaii.

Estimation of moisture migration in rammed earth based on entropy theory.

In the field of cultural relic protection, the migration of moisture will cause a series of adverse effects, such as disruption and crater eruption. Assessment of water migration status is the key to early warning and prevention of these problems. In an attempt for a solution, the whole process of moisture migration in rammed earth is studied by using the moisture migration initiation criterion based on entropy. We analyzed and compared the entropy change law of the infrared radiation temperature in the two main migration stages, and we made a judgment on whether the moisture state is in the steady equilibrium or in the process of dynamic migration. The results show that the moisture migration status can be identified quickly and in real time by using the moisture migration initiation criterion based on entropy. The results of this study provide a new method for judging the state of moisture migration in geotechnical engineering, especially in the field of cultural relic protection, which has very important practical significance.

Understanding the storage conditions and fluctuating eruption style of a young monogenetic volcano: Blue Lake crater (

Blue Lake crater (<3 ka) is monogenetic volcano that produced one of the youngest eruptions in the central Oregon Cascades. Understanding monogenetic volcano behavior – from storage through eruption – is imperative in planning for future eruptions. Here we combine physical volcanology and geochemistry to determine the pre-eruptive storage conditions, ascent rate, eruption style, and deposit distribution of this young eruption. We find that the eruption of Blue Lake was initially phreatomagmatic, producing lithic-rich fall deposits and thin surge deposits and excavating the maar crater, before transitioning rapidly to a final voluminous magmatic-volatile driven explosive eruption. The mapped fall deposit has an estimated volume of 3.9 × 107 m3 (2.2 × 107 m3 DRE) which suggests a VEI of 3. Although similar in magnitude (as measured by fall deposit volume) to many other recent cinder cone eruptions in the Cascades, the Blue Lake crater eruption lacks an effusive phase. The absence of lava flows may reflect the lack of evidence for syn-eruptive magma storage at shallow levels. Indeed, corrected volatile contents of olivine-hosted melt inclusions (2.9–4.2 wt% H2O, 910–1330 ppm CO2) are strikingly uniform and indicate storage and crystallization at a restricted pressure range (average ~ 235 MPa), equating to a depth of ~8.6 km. Melt inclusion geochemistry indicates that the basaltic andesite magma cooled and crystallized ~25% during storage at this pressure. Crystals in the Blue Lake magma show evidence of mixing with, or entrainment in, a more evolved magma. Feldspar crystals have large An-rich cores (An80–85) and abrupt An-poor rims (An60–70); olivine crystals have large, broad cores (~Fo82–84) and thin rims with lower Fo and NiO contents. Diffusion modeling of olivine zoning suggests that an intrusion event occurred ~10–60 days prior to eruption. Diffusive loss of H+ from melt inclusions was minimal (<1.3 wt% H2O) during magma ascent, from which we calculate minimum ascent times from 235 MPa of <1 day. Many inclusions indicate ascent times of <3 h, corresponding to ascent rates of ~1 to >13 m/s. This study illustrates the pre-eruptive and eruptive complexities of monogenetic volcanoes and highlights the minimal warning that may precede future eruptions.

Conduit dynamics of highly explosive basaltic eruptions: The 1085 CE Sunset Crater sub-Plinian events

Basaltic volcanoes produce a range of eruptive styles, from Strombolian to low-intensity fire fountaining to, much more rarely, highly explosive Plinian eruptions. Although the hazards posed by highly explosive eruptions are considerable, controlling mechanisms remain unclear, and thus improving our understanding of such mechanisms is an important research objective. To elucidate these mechanisms, we investigate the magma ascent dynamics of basaltic systems using a 1D numerical conduit model. We find that variations in magmatic pressure at depth play a key role in controlling modelled eruption characteristics. Our most significant result is that a decrease in pressure at depth, consistent with the emptying of a magma chamber, results in enhanced volatile exsolution and in deepening fragmentation depth. The corresponding decrease in conduit pressure ultimately produces a collapse of the conduit walls. This type of collapse may be a key mechanism responsible for the cessation of individual explosive eruptions, a notion previously explored for silicic eruptions, but never before for basaltic systems. Using previously published field and sample analysis to constrain model parameters, we simulate scenarios consistent with sub-Plinian eruptions, similar to those at Sunset Crater volcano in ~1085 CE in terms of mass eruption rates and duration. By combining these analyses with a chamber-emptying model, we constrain the size of the magma chamber at Sunset Crater to be on the order of tens of km3. During the 1085 CE Sunset Crater eruption, there were three main sub-Plinian events that erupted between 0.12 and 0.33 km3 of tephra (non-DRE), indicating that ~1% of the total chamber volume was erupted during each sub-Plinian pulse.

Shock wave induced nanocrystallization during the high current pulsed electron beam process and its effect on mechanical properties

In this paper, the effect of high current pulsed beam (HCPEB) treatment induced nanocrystallization via shock waves in the mechanical properties of Al-15Si alloy was studied in detail. First, many fine nanograins formed on the top surface of the HCPEB-treated hypereutectic Al-15Si alloy and showed radial arrangement around the centre of the crater during the HCPEB process as a result of the impact of the shock wave induced by crater eruption. Second, the cross-section analysis revealed that some plate-like eutectic Si phases in the heat-affected zone were broken, which was attributed to the repeated impact of the shock wave under high temperature conditions. Third, many nanograins (Al) were formed in the heat-affected zone, which could be tightly related to the shock wave impact during the HCPEB process. Finally, the mechanical properties of the Al-15Si alloy before and after HCPEB treatment were measured, and the results showed that the tensile strength of the HCPEB-treated Al-15Si alloy increased approximately 41.4% from 138.8 MPa for the initial sample to 196.2 MPa for the modified sample. Therefore, HCPEB treatment is a versatile technique for refining the surface microstructure of hypereutectic Al–Si alloys.

Cyclic oxidation behaviour of the Al2TiO5/TiO2/ZrO2 composite coating on Ti–6Al–4V alloy with plasma electrolytic oxidation

Al2TiO5/TiO2/ZrO2 plasma electrolytic oxidation coating deposited on the surface of Ti–6Al–4V alloy was prepared in NaAlO2–NaH2PO2–NaOH electrolytes system, which was doped with ZrO2 micro-particles by a kind of pulsed bipolar plasma electrolytic oxidation. The microstructure, surface morphology and phase composition of the Al2TiO5/TiO2/ZrO2 coatings were studied by SEM and XRD, respectively. Its cyclic oxidation behaviour was studied over the temperature of 1000°C for 100 hours in dry air. After high-temperature oxidation, the original crater eruption topography of plasma electrolytic oxidation coating has disappeared and it obviously took a decreasing tendency of both pore numbers and their diameters. The scales of original plasma electrolytic oxidation coating consisted mostly of Al2TiO5, R-TiO2 and α-Al2O3intermixed with small amounts of ZrO2 particles. They were transferred into R-TiO2, α-Al2O3 and ZrO2 with small amounts of Al2TiO5 after high-temperature oxidation procedure. The weight gains of plasma electrolytic oxidation composite coating increased linearly with the extended oxidation cycles.

Hisat’sinom: Ancient Peoples in a Land without Water

Hisat'sinom: Ancient Peoples in a Land without Water Christian E. Downum (Editor) School for Advanced Research Press, Santa Fe, NM, 2012 196 pp. $59.95 Cloth, $24.95 PaperThis is a well-written and beautifully illustrated volume focusing on a relatively small but geographically diverse portion of the US Southwest-the Sin Agua culture area on the Mogollon Rim and immediately east of the San Francisco Peaks and present-day Flagstaff, Arizona. The focus is principally on the interplay between the harsh environment and Native American adaptive resilience from 400 CE or the advent of agriculture to no later than 1300 CE. Although the Paleo-Indian and archaic periods are represented in this zone, the material manifestations found here are also apparent in other better known areas (Chapter 8). Two aspects set this region apart: the lack of water, even by US Southwest measures, and its societal crossroads location, linking the heartland of the Hohokam with that of the Anazasi of Chaco Canyon. Because of this setting, it captures in microcosm much of what is revealed about the ancient social history of the US Southwest more broadly.The book is composed of 20 well-crafted essays by 25 contributors introducing and developing a comprehensive and encompassing set of topics meaningful to both scholar and well-informed layperson. A primary strength of the volume is its thoughtful assessments by several Hopi authors drawing from their own accounts of the ethnohistoric record as well as the ethnographic present (Chapters 2, 3, and 14). The tensions between academic archaeology-the arti-facts-and the Hopi way-the ancestral stories and their long-lived occupants-are not dismissed. As Lyle Balenquay notes, being Hopi was not a right but a privilege, hard earned, at great cost of effort (p 12). Too, the role of Northern Arizona University and the Museum of Northern Arizona pervade the volume by way of faculty and staffcommitment during decades of survey and excavation in this region. Christian Downum has done a fine service in envisioning this book.The geological backdrop for the cultural geography revolves around Sunset Crater, a volcanic blow paleomagnetically dated to 1080 CE and active for no more than 50 years (Chapter 5). The archaeology is significantly identified by pre- and post-Sunset Crater, as the intensity of occupation and agriculture markedly spikes for a hundred and fifty years following the generous deposition of cinder covering an extensive area. This cinder mulch allowed gardens to retain dry farming moisture over the thinnest of soils when the elevated bedrock prevented the further percolation of water deeper and away from the shallow root systems of maize-the latter a clear staple for most all US Southwest ancestral populations. Gregory Brown (Chapter 16) shows how linear and sometimes rectilinear stone alignments were positioned to shield juvenile corn plants from the persistent and sometimes severe spring and summer winds, rather than oriented to the slope angles of the terrain; the latter correlation one usually made in the semiarid world where infrequent cloud bursts and subsequent erosional runoffare credited with linear or contour alignments of rock (cf. Evenari, Shanan, and Tadmor 1982).Historically, during the 30s and 40s, Harold Colton founded and directed the Museum of Northern Arizona, and along with John McGregor defined the Sinagua culture. The black sands associated with the 1080 CE blast were viewed as the catalyst for increased agricultural production and populations, with the significant in-migration of others from neighboring culture areas (Chapter 10). Recent assessments strongly suggest that actual movements of peoples were likely less pronounced, but the exchange of goods and the ideas that they revealed were a principal change in the region. Michael O'Hara's chapter (9) provides a highly condensed and helpful introduction to the material remains. Agricultural populations were well established prior to the Sunset Crater eruption most prominently identified at Winoma Village with 36 pithouses, a three-room pueblo and perhaps an early ballcourt. …

From crater eruption to surface purification of raw silicon: A treatment by pulsed electron beam

Abstract The high-current pulsed electron beam treatment can induce crater eruption at the impurity particle sites, thus providing an efficient method for surface purification. In the present work, raw silicon materials of 2N-, 5N- and 6N-purity levels are treated by this method for the objective of testing the surface purification effect through the crater eruption mechanism on silicon. The surface morphology evolution is followed to trace the crater development in relation to treatment parameters such as energy density (1.8, 2.0 and 3.0 J/cm2) and pulse number (1, 3, 5 pulses), and to the sample purity levels. It is confirmed that the amounts of craters reflect the purity level of the initial samples. Raman spectroscopy shows red shifts, up to 2.2 cm−1, caused by the tensile stress due to impurity re-dissolution. The accompanied transient temperature field is also simulated, which supports the crater eruption mechanism.

Continuous monitoring of Hawaiian volcanoes with thermal cameras

Continuously operating thermal cameras are becoming more common around the world for volcano monitoring, and offer distinct advantages over conventional visual webcams for observing volcanic activity. Thermal cameras can sometimes “see” through volcanic fume that obscures views to visual webcams and the naked eye, and often provide a much clearer view of the extent of high temperature areas and activity levels. We describe a thermal camera network recently installed by the Hawaiian Volcano Observatory to monitor Kīlauea’s summit and east rift zone eruptions (at Halema‘uma‘u and Pu‘u ‘Ō‘ō craters, respectively) and to keep watch on Mauna Loa’s summit caldera. The cameras are long-wave, temperature-calibrated models protected in custom enclosures, and often positioned on crater rims close to active vents. Images are transmitted back to the observatory in real-time, and numerous Matlab scripts manage the data and provide automated analyses and alarms. The cameras have greatly improved HVO’s observations of surface eruptive activity, which includes highly dynamic lava lake activity at Halema‘uma‘u, major disruptions to Pu‘u ‘Ō‘ō crater and several fissure eruptions.

Surface Nanocrystallization of 3Cr13 Stainless Steel Induced by High‐Current Pulsed Electron Beam Irradiation

The nanocrystalline surface was produced on 3Cr13 martensite stainless steel surface using high‐current pulsed electron beam (HCPEB) technique. The structures of the nanocrystallized surface were characterized by X‐ray diffraction and electron microscopy. Two nanostructures consisting of fine austenite grains (50–150 nm) and very fine carbides precipitates are formed in melted surface layer after multiple bombardments via dissolution of carbides and crater eruption. It is demonstrated that the dissolution of the carbides and the formation of the supersaturated Fe (C) solid solution play a determining role on the microstructure evolution. Additionally, the formation of fine austenite structure is closely related to the thermal stresses induced by the HCPEB irradiation. The effects of both high carbon content and high value of stresses increase the stability of the austenite, which leads to the complete suppression of martensitic transformation.

Investigation on Oxidation Resistance of NiCoCrAlY Coating Irradiated by High Current Pulsed Electron Beam

In this paper, the NiCoCrAlY bond-coats was deposited onto the DZ4 nickel-based superalloy substrate by using low-pressure Plasma Spraying (LPPS) process, and then the coats were irradiated by high-current pulsed electron beam (HCPEB). Phase structures and microstructure of the HCPEB-treated NiCoCrAlY coating were analyzed by SEM, XRD and EDAX. The present results showed that the coating surface was remelted after HCPEB treatments, became smooth, had crater eruption, and the coating hadn’t produced distinct residual stresses. The results of the isothermal oxidations experiment performed in 900°C static air revealed that the oxidation resistance of the coating was enhanced obviously after HCPEB-treated and the oxides were mainly Aluminum-oxides, but without HCPEB-treated, the oxides of coating also had Nickel-oxides.

Crater Eruption Induced by High Current Pulsed Electron Beam (HCPEB) Treatment

High current pulsed electron beam (HCPEB) is a fairly new technique for improving surface properties such as corrosion and wear resistances. One of the negative effects induced by HCPEB is the potential formation of craters on the surface of the HCPEB treated materials. These changes can impair the corrosion-resistance by promoting pitting. The mechanisms of nucleation and growth are detailed and the effect of the number of pulses on crater formation is discussed.

Correlations of volcanic ash texture with explosion earthquakes from vulcanian eruptions at Sakurajima volcano, Japan

We compare the texture of volcanic ash with the maximum amplitude of explosion earthquakes ( A eq) for vulcanian eruptions from Sakurajima volcano. We analyze the volcanic ash emitted by 17 vulcanian eruptions from 1974 to 1987. Using a stereoscopic microscope, we classify the glassy particles into smooth surface particles (S-type particles) and non-smooth surface particles (NS-type particles) according to their surface conditions—gloss or non-gloss appearance—as an indicator of the freshness of the particles. S-type particles are further classified into V-type particles (those including vesicles) and NV-type particles (those without vesicles) by means of examinations under a polarized microscopic of polished thin sections. Cross-correlated examinations against seismological data show that: 1) the number fraction of S-type particles (S-fraction) has a positive correlation with A eq, 2) the number ratio of NV-type particles to V-type particles (the N/V number ratio) has a positive correlation with A eq, and 3) for explosions accompanied with BL-type earthquake swarms, the N/V number ratio has a negative correlation with the duration of the BL-Swarms. BL-Swarms refer to the phenomenon of numerous BL-type earthquakes occurring within a few days, prior to an increase in explosive activity [Kamo, K., 1978. Some phenomena before the summit crater eruptions at Sakura-zima volcano. Bull. Volcanol. Soc. Japan., 23, 53–64]. The positive correlation between the N/V number ratio and A eq could indicate that a large amount of separated gas from fresh magma results in a large A eq. Plagioclase microlite textual analysis of NV-type particles from five explosive events without BL-Swarms shows that the plagioclase microlite number density (MND) and the L/ W (length/width) ratio have a positive correlation with A eq. A comparison between textural data (MND, L/ W ratio, crystallinity) and the result of a decompression-induced crystallization experiment [Couch, S., Sparks, R.S.J., Carroll, M.R., 2003. The kinetics of degassing-induced crystallization at Soufriere Hills volcano, Montserrat. J. Petrol., 44, 1477–1502.] suggests that a plagioclase microlite texture of volcanic ash from eruptions without BL-Swarms could be generated by a decompression of 100–160 MPa. If the MND is controlled by the water exsolution rate from melt, the positive correlation between the MND and A eq may suggest that A eq becomes large when the effective decompression is large and the water exsolution rate is high (from 6.2 × 10 − 5 to 1.9 × 10 − 4 wt.%/s). The estimated magma ascent rate ranges from 0.11 to 0.35 m/s, which is one order of magnitude faster than that of an effusive eruption, and one to three orders slower than those for a (sub-) plinian eruption. This suggests that the ascent rate of magma plays an important role in the occurrence of vulcanian eruptions. We propose a simple model for vulcanian eruptions at Sakurajima volcano that takes into account the correlation between the S-fraction and A eq.

The Middle-Pleistocene (~300 ka) Rodderberg maar-scoria cone volcanic complex (Bonn, Germany): eruptive history, geochemistry, and thermoluminescence dating

The Rodderberg volcanic complex (RVC) is located within the city limits of Bonn (Germany) approximately 20 km to the north of the Quaternary East Eifel Volcanic Field (EEVF). It is the product of intense phreatomagmatic volcanism forming a 90 m deep maar crater and strombolian eruptions. Deposit features indicate that the location of the vent(s) shifted from N to S during the strombolian phase. The erupted leucite-nephelinite magma (on the order of ca. 1 × 10−2 km3) was largely homogenous with minor, stratigraphically controlled, variation in olivine and clinopyroxene microphenocryst content. Stratigraphic evidence and thermoluminescence dating indicate that the RVC erupted during the glacial MIS 8 at around 300 ka. During this time, the EEVF experienced a transitional stage between two major phases of volcanic activity involving a change in magma sources. This is consistent with the RVC geochemical data which show affinities to both the older EEVF leucite-nephelinite association (430–380 ka) and the younger basanite association (<215 ka). In the Eifel, magma ascent through the upper crust is apparently linked to tectonic fractures. It may be speculated that a tectonically controlled diking event channeled magma to the north of the main EEVF and that the RVC represents an exceptional surficial expression of a significantly larger subsurface intrusion. This scenario would be consistent with recent observations of diking-related volcanism in the East African Rift zone and previously inferred models for magma ascent in similar intraplate volcanic fields.

B46 桜島火山の2006年6月昭和火口噴火前後に発生したモノクロマティック地震の特徴とモーメントテンソル解析(活動的火山と防災,日本火山学会2006年秋季大会)

B46 桜島火山の2006年6月昭和火口噴火前後に発生したモノクロマティック地震の特徴とモーメントテンソル解析(活動的火山と防災,日本火山学会2006年秋季大会)

Microstructures and phase formations in the surface layer of an AISI D2 steel treated with pulsed electron beam

The nanostructures and metastable phase transformations in the surface layer of an AISI D2 steel treated with high current pulsed electron beam (HCPEB) were investigated. The surface structure is marked by two distinct features, i.e. the formation of sub-micrometer fine austenite γ grains (50–150 nm), and the disappearance of carbides via dissolution and crater eruption. The γ phase directly grows from the melt and is retained down to room temperature. Although the cooling rate is as high as 10 7 K/s in our case, the martensitic transformation could completely be suppressed. Such an effect is due to the increased stability of the austenite phase through grain refinement and chemistry modification.

Selective surface purification via crater eruption under pulsed electron beam irradiation

This letter reports an interesting phenomenon associated with the high-current pulsed electron beam treatment:selective surface purification. The treatment induces crater eruptions that preferentially occur at irregular composition and structure sites. The eruptions of second phase inclusions naturally lead to the purification and homogenization of the melted surface layer. This improves significantly the corrosion resistance of NiTi and 316L alloys.

Improved pitting corrosion resistance of AISI 316L stainless steel treated by high current pulsed electron beam

This paper investigates the pitting corrosion behaviors in simulated body fluid of AISI 316L stainless steel treated by high current pulsed electron beam. The treatment induces crater eruptions that preferentially occur at MnS inclusions and produces a surface purification effect. The mixing in the melting process and the subsequent solute trapping effect during fast solidification process result in the homogenization of elements in the melted layer. Both crater eruption and composition homogenization contribute to the selective surface purification effect. As a result, the pitting corrosion resistance of the steel is significantly improved.

Relationship between tremor and volcanic activity during the Southeast Crater eruption on Mount Etna in early 2000

The Southeast Crater of Mount Etna (Italy) was characterized by a violent eruptive activity between 26 January and 24 June 2000. This activity produced 64 lava fountain episodes with repose periods from 3 hours to 10 days. We estimated a volume of about 15–20 × 106 m3 lava and at least 2–3 × 106 m3 of tephra. We compared the paroxysmal volcanic activity to its associated seismic signature: The high number of events highlighted a strict correlation between tremor and volcanic activity. Seismic and volcanic characteristics, such as the frequency of occurrence, the duration of lava fountains and the associated tremor energy, suggested the subdivision of the studied period into two stages separated by the 20 February event. Combining volcanic with seismic data, we observed some useful relationships among lava fountain height, sustained column height and Reduced Displacement; in addition, we found that the entire episode was well correlated with the duration of the amplitude increase. Computing the tremor energy linked to each event, the total energy associated with lava fountains episodes results in 76% of the energy released during the whole period. Finally, the different ratios among the overall spectral amplitude of the seismic signals of the stations located at different altitudes suggested to us the elaboration of a simple qualitative model to explain the dynamic behavior of the tremor source during the whole episode.

OLIVINE LIQUID RELATIONS OF LAVA ERUPTED BY KILAUEA VOLCANO FROM 1994 TO 1998: IMPLICATIONS FOR SHALLOW MAGMATIC PROCESSES ASSOCIATED WITH THE ONGOING EAST-RIFT-ZONE ERUPTION

From 1994 through 1998, the eruption of K¯ilauea, in Hawai'i, was dominated by steady-state effusion at Pu'u ' O'¯ o that was briefly disrupted by an eruption 4 km uprift at Napau Crater on January 30, 1997. In this paper, I describe the systematic relations of whole-rock, glass, olivine, and olivine-inclusion compositions of lava samples collected throughout this interval. This suit e comprises vent samples and tube-contained flows collected at variable distances from the vent. The glass composition of tube lava varies systematically with distance and allows for the vent-correction of glass thermometry and olivine-liquid KD as a function of tube-transport distance. Combined olivine-liquid data for vent samples and vent-corrected lava-tube samples are used to document pre-eruptive magmatic conditions. KD values determined for matrix glasses and forsterite cores define three types of olivine phenocrysts: type A (in equilibrium with host glass), type B (Mg-rich relative to host glass) and type C (Mg-p oor relative to host glass). All three types of olivine have a cognate association with melts that are present within the shallow m ag- matic plumbing system during this interval. During steady-state eruptive activity, the compositions of whole-rock, glass and mo st olivine phenocrysts (type A) all vary sympathetically over time and as influenced by changes of magmatic pressure within the summit-rift-zone plumbing system. Type-A olivine is interpreted as having grown during passage from the summit magma- chamber along the east-rift-zone conduit. Type-B olivine (high Fo) is consistent with equilibrium crystallization from bulk-roc k compositions and is likely to have grown within the summit magma-chamber. Lower-temperature, fractionated lava was erupted during non-steady-state activity of the Napau Crater eruption. Type-A and type-B olivine-liquid relations indicate that this lava is a mixture of rift-stored and summit-derived magmas. Post-Napau lava (at Pu'u '¯ O'¯ o) gradually increases in temperature and MgO content, and contains type-C olivine with complex zoning, indicating magma hybridization associated with the flushing of rift-stored components through the eruption conduit.