# 25 years of eruption: Looking back and ahead

Release Date:

January 3, 2008, marks the 25th anniversary of Kīlauea's ongoing Puu Oo-Kupaianaha eruption.

Spattering against the south rim of the perched channel.

(Public domain.)

Shortly after midnight on January 3, 1983, geologists from the U S Geological Survey's (USGS) Hawaiian Volcano Observatory (HVO) witnessed the opening of ground fissures in Kīlauea's east rift zone, where the first fountains of lava erupted to start a volcanologically-special quarter century.

Since the USGS began intensifying its monitoring efforts at HVO in the 1960s, the Puu Oo-Kupaianaha eruption is Kīlauea's largest and longest. Though we might expect that this eruption is among Kīlauea's most voluminous or long-lasting, where this eruption ranks overall in terms of erupted volume or duration is not clear. Nor has this eruption yet ended.

Except for the 5-year-long Mauna Ulu eruption occurring between 1969 and 1974, other east rift zone eruptions during the 20th century were relatively brief, lasting only days or weeks. Understanding why the current 25-year-old eruption has continued so long will be very important in the long run, and we expect that our improved monitoring capabilities will fuel our research and progress toward that understanding.

In addition to cell phones, microwave ovens, or ATMs, we all might easily agree that computer technology, the Internet, and the World-wide web are developments that have significantly changed our lifestyles and improved our access to information in the last 25 years. They have also significantly changed and improved our volcano monitoring capabilities, perhaps to the point where it might be easy to overlook the considerable work required to keep all the instruments and systems running.

Observed earthquake patterns determined where HVO geologists positioned themselves in the field in 1983 to record the start of the eruption. The data for this required manual playback of data tapes and viewing the data interactively before earthquake locations could be computed. To determine locations more rapidly, data were measured with rulers and hand-entered into computers, but this procedure still took the better part of an hour.

Now, preliminary earthquake locations are determined automatically and routinely available within minutes of an earthquake. Cell phone or pager earthquake messages are also sent, so, if reception is available, earthquake activity can be tracked from the field.

Thanks to Internet technologies, HVO geologic, gas, and geodetic - or "deformation" - monitoring have enjoyed far more significant improvements. Quite obviously, our ability to post information and share observations online has been greatly enhanced by the development and never-ending updating of HVO's web pages.

Kīlauea and Mauna Loa fans are no doubt very familiar with HVO's webcams. These provide round-the-clock visual monitors of the volcanoes, without demanding regular or frequent maintenance. The resulting detailed photographic record has greatly expanded HVO's ability to note changes at the remote eruption site beyond times when geologists are in the field.

Similarly, HVO's geodetic monitoring has exploited recent technologies to expand its capabilities and incorporate new monitoring approaches. Global Positioning System (GPS) volcano monitoring was introduced years after 1983. It began "campaign-style" with large amounts of fieldwork and helicopter support required to achieve the desired network coverage. Now, HVO maintains dozens of permanent GPS sites whose data are automatically transmitted and processed to afford near-real-time surface deformation measurements.

There were 4 tiltmeters in Kīlauea's east rift zone that recorded the start of the Puu Oo-Kupaianaha eruption. These were complemented with survey lines whose length-changes were measured by field crews timing laser beams reflected off distant targets. In comparison, this eruption's most recent large change in July 2007 was recorded by tiltmeters and over a dozen GPS receivers that automatically send data to HVO. Like earthquake and webcam data, GPS and tilt data are posted and available for viewing on HVO's webpages.

Beyond improvements to our monitoring, HVO staff are pursuing with our colleagues interpretive models and research based on the data that we collect. The computing capabilities of even desktop computers and the availability of higher quality data present exciting possibilities. An important goal is to see that our research further improves our monitoring as well as our interpretations.

Through January 2008, as part of Hawaii Volcanoes National Park's After Dark in the Park presentation series, HVO scientists will discuss geologic, geodetic, and seismic aspects of the 25-year Puu Oo-Kupaianaha eruption with four separate talks. Speakers, titles, and brief summaries of the presentations are available online.

Happy New Year to all!

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### Volcano Activity Update

Kīlauea summit and Puu Oo continued to deflate. Seismic tremor levels at the summit are elevated but are still at low levels. Summit sulfur dioxide emissions have also increased. Earthquakes were located mostly beneath Halemaumau Crater and the south flank faults.

On July 21, 2007, lava began erupting from a set of fissures on the east flank of Pu'u 'O'o. Eruptive activity soon stabilized at fissure D, 2.3 kilometers (1.4 mi) northeast of Pu'u 'O'o. For the last several months this lava was directed entirely into a perched channel, consisting of separate pools often separated by bridges of cooled lava. At dawn on November 21, lava began to erupt directly from fissure D, outside of the perched channel, creating the Thanksgiving Eve breakout (TEB) flow. Lava supply to the original perched channel has been, in part, redirected through this new outlet, cutting off supply to the eastward tube which had been feeding flows in the vicinity of Pu'u Kia'i through much of November.

The TEB flow has continued to build itself vertically and laterally over the last several weeks. During the past week the front of active TEB lava has advanced several hundred meters (or yards), with the currently active flow front reaching a distance of 1.5 km (0.9 mi) southeast of fissure D. The TEB flow consists of a primary shield over the fissure, with several satellitic shields along a line towards the southeast. Just north of the TEB flows, activity in the original perched channel has declined during the past week, with the most recent overflight showing no significant activity in the now vacated channel or on the seeps.

Minor incandescence in Pu'u 'O'o was observed for two nights in early December, but has otherwise been absent since Aug. 31. As in years past, Pu'u 'O'o likely is serving as a large chimney, beneath which lava is stored briefly and degassed substantially enroute to the erupting fissure. Sloughing of Pu'u 'O'o into its own crater since late August has left numerous fresh cracks on the north rim and south flank of the cone.

Vent areas are hazardous. Access to the eruption site, in the Puu Kahaualea Natural Area Reserve, is closed (http://www.state.hi.us/dlnr/chair/pio/HtmlNR/07-N076.htm).

One earthquake beneath Hawaii Island was reported felt within the past week. A magnitude-1.5 earthquake occurred at 6:57 a.m. H.s.t. on Tuesday, December 25, 2007, and was located 8 km (5 miles) southeast of Hookena at a depth of 12 km (7 miles).

Mauna Loa is not erupting. One earthquake was located beneath the summit. Extension between locations spanning the summit, indicating inflation, continues at steady, slow rates. The Mauna Loa webcam radio transmitter is buried in snow and is not operational.