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Volcanowatch

September 10, 2009

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Putting Kīlauea's current activity in perspective

Dr. Tom Wright contemplating the new vent within Halema`uma`u Crater.
Dr. Tom Wright contemplating the new vent within Halema`uma`u Crater.

Dr. Thomas L. Wright, former Scientist-in-Charge of HVO, spent the last two weeks in Hawai`i exchanging ideas and information with HVO scientists. "We're witnessing a unique time in Kilauea's history," Tom says, and he should know. Tom has devoted much of his career to studying Kilauea Volcano and is currently working on an epic project documenting the last 200 years of Kilauea's volcanic behavior.

Tom's first "live" eruption, that of Maka`opuhi Crater in 1965, formed a lava lake on the east rift zone. When the eruption ended, he took advantage of what he calls a "true outside laboratory" to produce a classic study on the cooling and crystallization of basaltic lava. "We started drilling into the lake as soon as the crust was safe to walk on," Tom recalls, which means that there was plenty of red stuff just a few inches beneath their feet.

Tom returned to HVO to serve as Scientist-in-Charge, in 1984, during the Mauna Loa eruption. Upon arriving from the mainland, he immediately donned a flight suit and boarded a helicopter to survey the erupting vents and lava flows.

After his term was over in 1991, he stayed on at HVO for another two years to continue working with Jane Takahashi on an annotated bibliography and database of papers about Hawaiian volcanism from 1779 to the present.

Tom's interest in Hawaiian volcanoes did not wane after leaving the islands. Together with another HVO alumnus, seismologist Fred Klein, he investigated records of earthquakes in Hawai`i before the establishment of modern seismic networks. This involved some serious detective work—poring through journals, missionary diaries, newspaper articles, and other hard-to-find references.

The resulting seismic catalog, along with Tom's other extensive historical research, laid the foundation for his current project: a 200-year interpretive history of Kilauea Volcano.

The study involves identifying and interpreting trends and patterns in seismic and deformation data and correlating them with volcanic activity to gain a better understanding of the volcano's magma supply system.

The study starts with the first written observations of volcanic activity at Kilauea in 1823. That was a spectacular time to be an observer at Kilauea's summit. A lava lake covered the entire caldera floor, with multiple vents within the caldera. Tom attributes this high level of summit activity to an extremely rapid rate of magma being supplied to the volcano.

Another period of high magma influx started in 1907, with renewed filling of Halema`um`au Crater, creating another summit lava lake. Lava lake activity ceased completely just before the climactic 1924 explosive eruption.

Tom reminds us that the 1924 eruption closely followed a large intrusion of magma into the lower east rift zone. The intrusion essentially "emptied" the magma storage reservoirs, starting another cycle of filling and a new eruptive style.

Over the 200-year history, Tom identifies several such cycles. Detailed investigation of seismic and deformation patterns reveal that major changes in eruptive style are generally a response to increased magma supply to the volcano.

From this long-term perspective, he thinks we may be seeing a new cycle of activity at Kilauea. The increase in magma supply we've observed since late 2003, the Father's Day intrusion, and new eruptive vents on the east rift zone in 2007 are distinctive markers of the transition, leading to the opening of the new vent at the summit.

Although features of each cycle may be similar, the exact accommodation the volcano makes to the changing conditions varies. Speaking of the current activity, Tom notes, "We've never seen sustained simultaneous eruptions at the summit and on the east rift zone [in the recorded past]."

Just how the volcano is achieving equilibrium during these past two years of sustained summit and east rift zone eruptions is still a subject of debate. What is certain is that the long-term context and insights into the internal workings of the volcano provided by Tom's work adds much fuel and many puzzle pieces to the discussion.

Kīlauea Activity Update

Lava continues to erupt from the TEB vent, on Kīlauea's east rift zone and flow through tubes to the ocean at Waikupanaha. A lava breakout from the tube near the top of the Royal Gardens subdivision has been active since September 2. The flow has progressed downslope only a short distance, its terminus burning forested kipuka along the eastern edge of the TEB flow.

Faint glow above the vent at Kīlauea's summit has been visible at night, though its brightness, as of September 10, had diminished compared to its appearance earlier in the week. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.

One earthquake beneath Hawai`i Island was reported felt this past week. A magnitude-3.3 earthquake occurred at 7:22 p.m., H.s.t., on Wednesday, September 9, 2009, and was located 8 km (5 miles) southeast of Ho`okena at a depth of 12 km (7 miles).

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.

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Updated: October 1, 2009 (pnf)