USGS Technical Announcement: 200 Years of Magma at Kīlauea Volcano Described in New Book
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This release can be found in the USGS Newsroom at: http://www.usgs.gov/newsroom/article.asp?ID=3995.
News Release | |||||
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Technical Announcement:
200 Years of Magma at Kīlauea Volcano Described in New Book
| Professional Paper 1806: Two Hundred Years of Magma Transport and Storage at Kīlauea Volcano, Hawaiʻi, 1790–2008 |
ISLAND OF HAWAIʻI, Hawaiʻi — A new book that summarizes the Kīlauea magma system is now available online, with printed copies to follow soon. The U.S. Geological Survey monograph summarizes the evolution of the internal plumbing of Kīlauea Volcano on the Island of Hawaiʻi from the first documented eruption in 1790 to the explosive eruption of March 2008 in Halemaʻumaʻu Crater.
For the period before the founding of the Hawaiian Volcano Observatory in 1912, the authors rely on written observations of eruptive activity, earthquake swarms, and periodic draining of magma from the lava lake present in Kīlauea Caldera by missionaries and visiting scientists. After 1912 the written observations were supplemented by continuous measurement of tilting of the ground at Kīlauea’s summit and by a continuous instrumental record of earthquakes, both measurements made during 1912–56 by a single pendulum seismometer housed on the northeast edge of Kīlauea’s summit. Scientific interpretations become more robust following the installation of seismic and deformation networks in the 1960s. A major advance in the 1990s was the ability to continuously record and telemeter ground deformation to allow its precise correlation with seismic activity before and after eruptions, intrusions, and large earthquakes.
In Kīlauea’s 200-year history, USGS scientists and authors of the new volume, Thomas Wright and Fred Klein, identify three regions of the volcano in which magma is stored and supplied from below. Source 1 is at 1-km depth or less beneath Kīlauea’s summit and fed Kīlauea’s summit lava lakes throughout most of the 19th century and again from 1907 to 1924. Source 1 was used up in the series of small Halemaʻumaʻu eruptions following the end of lava-lake activity in the summit collapse of 1924. Source 2 is the magma reservoir at a depth of 2–6 km beneath Kīlauea’s summit that has been imaged by seismic and deformation measurements beginning in the 1960s. This source was first identified in the summit collapses of 1922 and 1924. Source 3 is a diffuse volume of magma-permeated rock between 5 and 11 km depth beneath the east rift zone and above the near-horizontal fault at the base of the Kīlauea edifice.
Kīlauea’s history can be considered in cycles of equilibrium, crisis, and recovery. The approach of a crisis is driven by a magma supply rate that greatly exceeds the capacity of the plumbing to deliver magma to the surface. Crises can be anticipated by inflation measured at Kīlauea’s summit coupled with an increase in overall seismicity, particularly manifest by intrusion and eruption in the southwest sector of the volcano. Unfortunately the nature of the crisis—for example, a large earthquake, new eruption, or edifice-changing intrusion—cannot be specified ahead of time. The authors conclude that Kīlauea’s cycles are controlled by nonlinear dynamics, which underscores the difficulty in predicting eruptions and earthquakes.
Highlights of interpretations for the period prior to 1952 are:
• Prior to and including 1924, major subsidence events include draining of the deep magma system identified beneath Kīlauea’s East Rift Zone. 1924 is the last such occurrence.
• A massive intrusion on the lower east rift zone preceding the 1924 phreatic activity at Kīlauea’s summit stabilized the south flank and the present magmatic system.
• The 1952 eruption was preceded by deep earthquakes associated with the magma supply path from the mantle resulting in the beginning of a steady increase in magma supply rate extending to 2008. A large earthquake swarm on the offshore part of Kīlauea’s south flank in the months before the 1952 eruption ushered in the modern era of seaward spreading.
Interpretations in the post-1952 period are based on connecting events over a far longer time period than the duration of any one person’s tenure on the USGS Hawaiian Volcano Observatory staff.
Highlights are:
• Kīlauea’s shallow magma system is envisioned as a small molten core surrounded by a partially molten matrix able to record both short- and long-period seismicity.
• Magma coming from the mantle enters the rift zone before it reaches the molten core and appears in rift eruptions before it is seen as a summit eruption.
• Earthquake swarms beneath Kīlauea’s south flank precede as well as succeed shallow intrusions, supporting the modern idea of deep magma pressure being exerted from beneath the East Rift Zone.
• Prior to the M7 south flank earthquake on November 29, 1975 south flank spreading was driven by Kīlauea’s magma supply. Following the earthquake the spreading rate was decoupled from the still increasing magma supply rate.
• The seismic signatures of “suspected deep intrusions” in the monograph are equated with similar signatures that characterize “slow-slip” or “silent” earthquakes. The occurrence of such events is inferred to extend as far back as the 1960s well before continuous geodetic monitoring could identify correlated spreading steps.
• Major changes in Kīlauea’s behavior, such as ends of long eruptions, large south flank earthquakes or changes in eruptive style are anticipated by increased seismic activity on the southwest side of the volcano. The nature of the coming event is not specified, which emphasizes the uncertainties in eruption and earthquake forecasting, even in an increasingly well-monitored, but yet imperfectly understood volcano.
Citation: Wright, T.L., and Klein, F.W., 2014, “Two hundred years of magma transport and storage at Kīlauea Volcano, Hawai'i, 1790-2008,” U.S. Geological Survey Professional Paper 1806, 240 p., plus 8 digital appendixes.
Appendices include yearly time-series seismic plots and map plots for all intrusion-related earthquake swarms covered in the text. Earthquakes are color-coded to indicate those preceding, during, and following the intrusion.
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