Oxygen Isotope Evidence for Chemical Interaction of Ki lauea Historical Magmas with Basement Rocks

Klauea historical summit lavas have a wide range in matrix ¹⁸O_VSMOWvalues (4·9–5·6) with lower values in rockserupted following a major summit collapse or eruptive hiatus.In contrast, ¹⁸O values for olivines in most of these lavasare nearly constant (5·1 ± 0·1). The disequilibriumbetween matrix and olivine ¹⁸O values in many samples indicatesthat the lower matrix values were acquired by the magma afterolivine growth, probably just before or during eruption. BothMauna Loa and Klauea basement rocks are the likely sources ofthe contamination, based on O, Pb and Sr isotope data. However,the extent of crustal contamination of Klauea historical magmasis probably minor (< 12%, depending on the assumed contaminant)and it is superimposed on a longer-term, cyclic geochemicalvariation that reflects source heterogeneity. Klauea's heterogeneoussource, which is well represented by the historical summit lavas,probably has magma ¹⁸O values within the normal mid-ocean ridgebasalt mantle range (5·4–5·8) based on thenew olivine ¹⁸O values. KEY WORDS: Hawaii; Klauea; basalt; oxygen isotopes; crustal contamination     

Transient deformation following the 30 January 1997 dike intrusion at Kīlauea volcano,Hawai’i

On 30 January 1997 an intrusion on Kīlauea volcano opened a new fissure within the East Rift Zone (ERZ) at Nāpau Crater, 3 km uprift from the ongoing eruptions at Pu’u ’Ō’ō. The fissure eruption lasted 22 h and opened a 5.1 km long, nearly vertical dike 1.9 m, extending from the surface to a depth of 2.4 km (Owen et al. 2000b). During the eruption, the lava pond at Pu’u ’Ō’ō drained, and eruptions ceased there. Pu’u ’Ō’ō eventually refilled in late February and eruptions resumed there on 28 March 1997. Continuous GPS data show a large transient following the 30 January 1997 dike intrusion. After lengthening 40 cm during the initial eruption, the baseline between two stations spanning the ERZ lengthened an additional 10 cm over the following 6 months. A coastal station KAEP also exhibited transient deformation, as it continued to move southward (5 cm) over the same 6-month period. The baseline between two stations spanning Kīlauea’s summit caldera contracted sharply during the eruption, but gradually recovered to slightly longer than its previous length 2 months after the intrusion. We use the extended network inversion filter (McGuire and Segall 2003) to invert continuous GPS data for volume change of a spherical pressure source under Kīlauea’s summit, opening distribution on a nearly vertical dike in the ERZ and potential slip on a decollement 9 km beneath the south flank. Following the 30 January intrusion, rift extension continued below the initial dike intrusion for the duration of the transient. Decollement slip, regardless of its assumed depth, is not required to fit the data. The modeled transient summit reinflation and rift opening patterns under Nāpau crater coincide with changes in observed behavior of Pu’u ’Ō’ō’s lava pond. Rift opening accelerated while Pu’u ’Ō’ō eruptions paused and began to decelerate after the lava pond reappeared nearly a month after the Nāpau eruption. The transient deformation is interpreted as resulting from shallow accommodation of the new dike volume.     

Community preparedness for lava flows from Mauna Loa and Hualālai volcanoes,Kona, Hawai‘i

Lava flows from Mauna Loa and Huallai volcanoes are a major volcanic hazard that could impact the western portion of the island of Hawaii (e.g., Kona). The most recent eruptions of these two volcanoes to affect Kona occurred in a.d. 1950 and ca. 1800, respectively. In contrast, in eastern Hawaii, eruptions of neighboring Klauea volcano have occurred frequently since 1955, and therefore have been the focus for hazard mitigation. Official preparedness and response measures are therefore modeled on typical eruptions of Klauea.The combinations of short-lived precursory activity (e.g., volcanic tremor) at Mauna Loa, the potential for fast-moving lava flows, and the proximity of Kona communities to potential vents represent significant emergency management concerns in Kona. Less is known about past eruptions of Huallai, but similar concerns exist. Future lava flows present an increased threat to personal safety because of the short times that may be available for responding.Mitigation must address not only the specific characteristics of volcanic hazards in Kona, but also the manner in which the hazards relate to the communities likely to be affected. This paper describes the first steps in developing effective mitigation plans: measuring the current state of peoples knowledge of eruption parameters and the implications for their safety. We present results of a questionnaire survey administered to 462 high school students and adults in Kona. The rationale for this study was the long lapsed time since the last Kona eruption, and the high population growth and expansion of infrastructure over this time interval. Anticipated future growth in social and economic infrastructure in this area provides additional justification for this work.The residents of Kona have received little or no specific information about how to react to future volcanic eruptions or warnings, and short-term preparedness levels are low. Respondents appear uncertain about how to respond to threatening lava flows and overestimate the minimum time available to react, suggesting that personal risk levels are unnecessarily high. A successful volcanic warning plan in Kona must be tailored to meet the unique situation there.     

Kīlauea summit overflows: their ages and distribution in the Puna District, Hawai'i

 The tube-fed pāhoehoe lava flows covering much of the northeast flank of Kīlauea Volcano are named the 'Ailā'au flows. Their eruption age, based on published and six new radiocarbon dates, is approximately AD 1445. The flows have distinctive paleomagnetic directions with steep inclinations (40°–50°) and easterly declinations (0°–10°E). The lava was transported ∼40 km from the vent to the coast in long, large-diameter lava tubes; the longest tube (Kazumura Cave) reaches from near the summit to within several kilometers of the coast near Kaloli Point. The estimated volume of the 'Ailā'au flow field is 5.2±0.8 km³, and the eruption that formed it probably lasted for approximately 50 years. Summit overflows from Kīlauea may have been nearly continuous between approximately AD 1290 and 1470, during which time a series of shields formed at and around the summit. The 'Ailā'au shield was either the youngest or the next to youngest in this series of shields. Site-mean paleomagnetic directions for lava flows underlying the 'Ailā'au flows form only six groups. These older pāhoehoe flows range in age from 2750 to <18,000 BP, and the region was inundated by lava flows only three times in the past 5000 years. The known intervals between eruptive events average ∼1600 years and range from ∼1250 years to >2200 years. Lava flows from most of these summit eruptions also reached the coast, but none appears as extensive as the 'Ailā'au flow field. The chemistry of the melts erupted during each of these summit overflow events is remarkably similar, averaging approximately 6.3 wt.% MgO near the coast and 6.8 wt.% MgO near the summit. The present-day caldera probably formed more recently than the eruption that formed the 'Ailā'au flows (estimated termination ca. AD 1470). The earliest explosive eruptions that formed the Keanakāko'i Ash, which is stratigraphically above the 'Ailā'au flows, cannot be older than this age. Received: 10 October 1998 / Accepted: 12 May 1999     

Cooling and crystallization of lava in open channels, and the transition of Pāhoehoe Lava to 'A'ā

 Samples collected from a lava channel active at Kīlauea Volcano during May 1997 are used to constrain rates of lava cooling and crystallization during early stages of flow. Lava erupted at near-liquidus temperatures (∼1150  °C) cooled and crystallized rapidly in upper parts of the channel. Glass geothermometry indicates cooling by 12–14  °C over the first 2 km of transport. At flow velocities of 1–2 m/s, this translates to cooling rates of 22–50  °C/h. Cooling rates this high can be explained by radiative cooling of a well-stirred flow, consistent with observations of non-steady flow in proximal regions of the channel. Crystallization of plagioclase and pyroxene microlites occurred in response to cooling, with crystallization rates of 20–50% per hour. Crystallization proceeded primarily by nucleation of new crystals, and nucleation rates of ∼10⁴/cm³s are similar to those measured in the 1984 open channel flow from Mauna Loa Volcano. There is no evidence for the large nucleation delays commonly assumed for plagioclase crystallization in basaltic melts, possibly a reflection of enhanced nucleation due to stirring of the flow. The transition of the flow surface morphology from pāhoehoe to 'a'ā occurred at a distance of 1.9 km from the vent. At this point, the flow was thermally stratified, with an interior temperature of ∼1137  °C and crystallinity of ∼15%, and a flow surface temperature of ∼1100  °C and crystallinity of ∼45%. 'A'ā formation initiated along channel margins, where crust was continuously disrupted, and involved tearing and clotting of the flow surface. Both observations suggest that the transition involved crossing of a rheological threshold. We suggest this threshold to be the development of a lava yield strength sufficient to prevent viscous flow of lava at the channel margin. We use this concept to propose that 'a'ā formation in open channels requires both sufficiently high strain rates for continued disruption of surface crusts and sufficient groundmass crystallinity to generate a yield strength equivalent to the imposed stress. In Hawai'i, where lava is typically microlite poor on eruption, these combined requirements help to explain two common observations on 'a'ā formation: (a) 'a'ā flow fields are generated when effusion rates are high (thus promoting crustal disruption); and (b) under most eruption conditions, lava issues from the vent as pāhoehoe and changes to 'a'ā only after flowing some distance, thus permitting sufficient crystallization. Received: 3 September 1998 / Accepted: 12 April 1999     

Lava bubble-wall fragments formed by submarine hydrovolcanic explosions on Lō'ihi Seamount and Kīlauea Volcano

 Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted on Lō'ihi Seamount and along the submarine east rift zone of Kīlauea Volcano. The limu o Pele fragments are undegassed with respect to H₂O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths by cooling-contraction granulation. The limu o Pele fragments from Lō'ihi Seamount are dominantly tholeiitic basalt containing 6.25–7.25% MgO. None of the limu o Pele samples from Lō'ihi Seamount contains less than 5.57% MgO, suggesting that higher viscosity magmas do not form lava bubbles. The dissolved CO₂ and H₂O contents of 7 of the limu o Pele fragments indicate eruption at 1200±300 m depth (120±30 bar). These pressures exceed that generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing conditions, at pressures as great as 120 bar. Received: 22 December 1998 / Accepted: 16 July 1999     

Hawaiian oral tradition describes 400 years of volcanic activity at Kīlauea

Culturally significant oral tradition involving Pele, the Hawaiian volcano deity, and her youngest sister Hi'iaka may involve the two largest volcanic events to have taken place in Hawai'i since human settlement: the roughly 60-year-long ‘Ailā’au eruption during the 15th century and the following development of Kīlauea's caldera. In 1823, Rev. William Ellis and three others became the first Europeans to visit Kīlauea's summit and were told stories about Kīlauea's activity that are consistent with the Pele–Hi'iaka account and extend the oral tradition through the 18th century. Recent geologic studies confirm the essence of the oral traditions and illustrate the potential value of examining other Hawaiian chants and stories for more information about past volcanic activity in Hawai‘i.     

Implications for eruptive processes as indicated by sulfur dioxide emissions from K lauea Volcano, Hawai‘i, 1979–1997

K lauea Volcano, Hawai‘i, currently hosts the longest running SO₂ emission-rate data set on the planet, starting with initial surveys done in 1975 by Stoiber and his colleagues. The 17.5-year record of summit emissions, starting in 1979, shows the effects of summit and east rift eruptive processes, which define seven distinctly different periods of SO₂ release. Summit emissions jumped nearly 40% with the onset (3 January 1983) of the Pu‘u ‘ ‘ -K paianaha eruption on the east rift zone (ERZ). Summit SO₂ emissions from K lauea showed a strong positive correlation with short-period, shallow, caldera events, rather than with long-period seismicity as in more silicious systems. This correlation suggests a maturation process in the summit magma-transport system from 1986 through 1993. During a steady-state throughput-equilibrium interval of the summit magma reservoir, integration of summit-caldera and ERZ SO₂ emissions reveals an undegassed volume rate of effusion of 2.1×10⁵ m³/d. This value corroborates the volume-rate determined by geophysical methods, demonstrating that, for K lauea, SO₂ emission rates can be used to monitor effusion rate, supporting and supplementing other, more established geophysical methods. For the 17.5 years of continuous emission rate records at K lauea, the volcano has released 9.7×10⁶ t (metric tonnes) of SO₂, 1.7×10⁶ t from the summit and 8.0×10⁶ t from the east rift zone. On an annual basis, the average SO₂ release from K lauea is 4.6×10⁵ t/y, compared to the global annual volcanic emission rate of 1.2×10⁷ t/y.     

Comment on " Volume of magma accumulation or withdrawal estimated from surface uplift or subsidence, with application to the 1960 collapse of Kīlauea volcano" by P. T. Delaney and D. F. McTigue

 In volcanoes that store a significant quantity of magma within a subsurface summit reservoir, such as Kīlauea, bulk compression of stored magma is an important mode of deformation. Accumulation of magma is also accompanied by crustal deformation, usually manifested at the surface as uplift. These two modes of deformation – bulk compression of resident magma and deformation of the volcanic edifice – act in concert to accommodate the volume of newly added magma. During deflation, the processes reverse and reservoir magma undergoes bulk decompression, the chamber contracts, and the ground surface subsides. Because magma compression plays a role in creating subsurface volume to accommodate magma, magma budget estimates that are derived from surface uplift observations without consideration of magma compression will underestimate actual magma volume changes. Received: 30 September 1998 / Accepted: 27 July 1999     

A frozen record of density-driven crustal overturn in lava lakes: the example of Kīlauea Iki 1959

Lava lakes are found at basaltic volcanoes on Earth and other planetary bodies. Density-driven crustal foundering leading to surface renewal occurs repeatedly throughout the life of a lava lake. This process has been observed and described in a qualitative sense, but due to dangerous conditions, no data has been acquired to evaluate the densities of the units involved. Kīlauea Iki pit crater in Hawai`i houses a lava lake erupted during a 2 month period in 1959. Part of the surface of the Kīlauea Iki lake now preserves the frozen record of a final, incomplete, crustal-overturn cycle. We mapped this region and sampled portions of the foundering crust, as well as overriding and underlying lava, to constrain the density of the units involved in the overturn process. Overturn is driven by the advance of a flow front of fresh, low-density lava over an older, higher density surface crust. The advance of the front causes the older crust to break up, founder, and dive downwards into the lake to expose new, hot, low-density lava. We find density differences of 200 to 740 kg/m³ between the foundering crust and over-riding and under-lying lava respectively. In this case, crustal overturn is driven by large density differences between the foundering and resurfacing units. These differences lead, inevitably, to frequent crustal renewal: simple density differences between the surface crust and underlying lake lava make the upper layers of the lake highly unstable. Work originally presented at the American Geophysical Union Fall Meeting in San Francisco, California on December 11, 2007.