VOLCANO WATCH: Understanding Hawaiian Volcanism
Modern science could not exist without exchange of data and ideas. The exchange can be informal––at meetings and in casual conversations––or formal––in papers or books that can be studied and debated for years to come. The old axiom, publish or perish, is as true for science as it is for scientists.
The science of Hawaiian volcanoes is in good shape, judging from three recent and hefty technical books.
Richly illustrated Characteristics of Hawaiian Volcanoes (USGS Professional Paper 1801) marked HVO’s centennial in 2014 and presents advances in knowledge since publication of Volcanism in Hawaii (USGS Professional Paper 1350) commemorating HVO’s 75th anniversary in 1987.
Hawaiian Volcanoes: From Source to Surface (American Geophysical Union Monograph 219), published in early 2015, also covers a variety of subjects on Hawaiian volcanism and its relation to other volcanic systems. It also includes key questions to help guide further research.
The most recent new book, Two Hundred Years of Magma Transport and Storage at Kilauea Volcano, Hawai‘i, 1790–2008 (USGS Professional Paper 1806), by former HVO scientists Tom Wright and Fred Klein, won first place in the Technical or Statistical Report category in the Blue Pencil and Gold Screen Awards, sponsored by the National Association of Government Communicators. The book covers Kilauea history from 1790 through 2008, including the first known and ongoing episode of prolonged activity at both the summit and east rift zone of Kilauea.
Using continuous records of daily earthquakes and ground tilt measurements dating back to the founding of HVO in 1912, Wright and Klein trace the evolution of Kilauea’s magmatic plumbing. They describe the effects of this evolving system upon the sequence of eruptions, intrusions, and seaward movement of the volcano’s south flank over time.
Among the many significant events covered in the book, in 1924, a great intrusion of magma occurred at Kilauea, followed by an immense explosion at the summit. According to the authors, the events of 1924––including steam explosions from an enlarging Halema‘uma‘u Crater and the large intrusion into the lower east rift zone––stabilized the Kilauea magmatic system and subsequently enabled seaward movement of the south flank.
Another significant event, the Kalapana earthquake of November 29, 1975, changed the relationship between magma supply and spreading (or seaward motion) of Kilauea’s south flank. Before the earthquake, increases in magma supply drove increases in the spreading rate. Following the earthquake, the magma supply rate continued to increase while the spreading rate remained constant and intrusions were favored over eruptions. The change in pattern suggests that intruded magma was refilling subsurface space created by the earthquake and that flank spreading can at times be influenced by gravity alone.
“Slow-slip” earthquakes––motion of the shallow crust at rates slower than during typical earthquakes but faster than normal flank spreading rates––have been recognized at Kilauea only recently, but Wright and Klein note possible examples from seismic signatures as early as the 1960s.
Wright and Klein also present evidence of a complementary nature of Kilauea’s activity with that of its much larger neighbor, Mauna Loa. This relationship may explain the absence of eruptions at Mauna Loa since 1984 when Kilauea has been exceptionally active. Such a pattern is recognized going back at least 2,500 years, according to the work of HVO scientist Frank Trusdell.
Finally, the authors propose cycles of “crisis and relief” at Kilauea. Crises are marked by increased seismicity and uplift of the southwest sector of the volcano. Relief comes in a variety of forms: large south-flank earthquakes, the ending or beginning of eruptive activity, or intrusions correlated with changes in eruption style. Such varied outcomes render long-term forecasts of damaging earthquakes or eruptions especially difficult––all part of the hazard of living on a volcanically active island.
As these books demonstrate, Hawai‘i is a world-class laboratory for studies of basaltic volcanism and its impacts on our communities. Data and ideas from these publications will no doubt spur important scientific discussion, further research, and ultimately increased understanding.
Volcano Activity Update
Kilauea continues to erupt at its summit and East Rift Zone. The summit lava lake level varied between about 45 and 70 m (148–230 ft) below the vent rim within Halemaʻumaʻu Crater. On the East Rift Zone, scattered lava flow activity remained within about 6 km (4 mi) of Puʻu ʻŌʻō.
Mauna Loa is not erupting. The seismicity rate continues above long term background, though it has not increased above rates observed in recent months. In the last week, earthquakes occurred mostly beneath Mauna Loa’s upper Southwest Rift Zone at depths less than 5 km (3 miles). Continuous GPS measurements continue to show deformation consistent with inflation of magma reservoirs beneath Mauna Loa.
One earthquake was reported felt in the past week across the Hawaiian Islands. On December 1, at 9:02 am a magnitude 3.1 earthquake occurred 19 mi (30 km) west-northwest of Hilo at a depth of 17 mi (28 km).
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey`s Hawaiian Volcano Observatory.