Understanding the forces controlling basaltic explosive eruptions is of fundamental importance in order to improve understanding of the range of behaviors of our most frequently active volcanoes and to assess hazards of future explosive events. The summit of Kîlauea is the site of large and growing volcano-tourism (e.g., 5000 visitors/day at the overlook at Jaggar Museum), and there is a public need both for better knowledge of the volcanoes' behavior and improved forecasting of the likely course of future eruptions. Although not its usual style, explosive eruptions have punctuated Kîlauea's history, with five moderately large events since 1500 CE.
The study quantifies and models the dominant factors that determine explosive eruptive behavior at Kilauea volcano, through a study of the eruptive products from three plume-forming and fountaining eruptions. The events are episode 1 of the highest historical fountaining eruption at Kîlauea, the 1959 Kîlauea Iki eruption, a much earlier powerful fountaining eruption in 1480 CE and a powerful; plume-forming eruption in 1635 CE.
The novelty of the approach lies in using new 'rate-meters' to estimate likely durations of magma ascent beneath the volcano to arrive at the influence of this residence time on the ultimate 'fate' of the magma. The investigators will study microtextures (vesicles and microlites), volatiles in melt inclusions, and embayments in eruptive products.
In addition to direct support for 3 graduate students and undergraduate students, results will contribute to educational outreach efforts anchored on development of volcanology classes at University of Hawaii, Columbia University and Rice University. The proposal involves exchange of material and ideas between five institutions to the benefit of young researchers, and undergraduate and graduate classes. Our results will be widely disseminated via the Internet using linked web sites hosted by Hawaiian Volcano Observatory and NSF-funded institutions.
K?lauea volcano in Hawaii is among the most intensely monitored, continually active volcanoes in the world and the location of large and growing volcano-tourism operation. Hawaii Volcanoes National Park, for example, records about 5000 visitors per day to the summit of K?lauea. These facts drove this study looking for deeper understanding of variations in the volcanoes’ behavior. It focused on 3 eruptions, one typical and one very powerful example of classical Hawaiian fountains and one more powerful explosion that produced an eruption plume reaching to elevations of at least 8 to 10 km. The project featured two possible explanations for this variability, differences in the original abundance of volcanic gas in the erupted magmas versus contrasting speeds of ascent of the magma through the shallow plumbing system of the volcano. In the former hypothesis higher abundances of dissolved gases would drive more powerful explosions whereas in the later faster ascent rates permit higher gas pressures to develop in the case of the stronger eruptions. Concentrations of dissolved gas trapped in glass relics sealed inside crystals showed that all three eruptions were of magmas with similar initial gas contents. The first approach to the second hypothesis looked to estimate ascent rates directly by measuring the extent to which gas dissolved in glass trapped in the magma was able to diffuse outward and stay in equilibrium. This method showed that magma that fed the weakest fountain eruptions ascended up to four times more slowly than that for the powerful explosive eruption. This directly supports the second explanation. In the second approach the number and sizes of gas bubbles trapped in the erupted material were measured, to look at the implications of the contrasting rates of ascent of the parent magma. They show that the lower, more typical fountaining eruption involved the simplest pattern of bubble formation accompanying decreases of pressure as the magma approached the surface. In the lead-up to the higher fountaining event, faster ascent delayed the onset of bubble formation leading to a short more intense period of bubble formation and growth that likely fueled the higher fountains the highest ever. The ascent rates estimated here indicate magma rise times on the order of minutes to hours from a few kilometers depth prior to the high fountains and more explosive eruptions. Such rapid run-ups to eruptions challenge most existing techniques for volcano monitoring and informing the public. Results of this work have been disseminated to the science community in the form of conference presentations and publications, and to the public through lectures and interviews with the media.
