# Volcano Watch — Professor Jaggar Would Have Loved This View

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Unusual, tantalizing, mesmerizing. Adrenaline-spiking, mid-life crisis(?). These words have been used in our recent Volcano Watch reports as we present our observations and describe Kīlauea Volcano's behaviors related to and following the explosion that occurred at Halemaumau on March 19. The event has definitely been unique in our modern era of volcano watching.

Gas geochemist Jeff Sutton does a duty shift in the HVO tower keeping an eye on the Halemaumau vent.

(Public domain.)

It is important to recognize that the recent explosions on March 19, April 9, and April 16 are all quite small, compared to Halemaumau's previous explosive sequence in 1924. We also need to understand that Halemaumau prior to 1924 was quite different from now, as it then contained an active lava lake.

At the same time, what we are experiencing is exactly why Thomas Jaggar established HVO at Kīlauea in 1912.

The offices and labs of the U S Geological Survey's Hawaiian Volcano Observatory - modernized in 1987 and named the Reginald T Okamura Building in 2002 - are perched at cliff's edge, overlooking Kīlauea's summit caldera with a view into Halemaumau.

Perhaps the most recognized feature of the Okamura Building is its tower providing a 360? view around HVO. Interestingly, the current Halemaumau activity is the first opportunity to observe and study an eruption from the tower since it was built,. Since March 19, HVO staff have maintained a round-the-clock caldera watch to observe and record changes occurring in Halemaumau. Visiting scientists Wendy McCausland, Mike Doukas, and Dan Dzurisin (former HVO staffer) from the USGS's Cascades Volcano Observatory have provided crucial support by coming to HVO and manning the tower through the long midnight shift.

Time-lapse and video cameras have been mounted in the tower to record any visible changes at the vent. Images from the webcam are available on HVO's public website at http://hvo.wr.usgs.gov/cam3/ along with Kīlauea eruption updates at http://volcano.wr.usgs.gov/kilaueastatus.php . The most fun piece of equipment is a tripod-mounted, 2-foot-long pair of binoculars.

Also set up in the tower since March 19 is a computer with network access to all of HVO's monitoring data streams. Displays of photographic, gas, geodetic, seismic, and thermal data are only a few mouse clicks and keystrokes away. Besides the obvious convenience, being able to look at diverse data on a single computer terminal - instead of running different programs on a number of different computers - affords the opportunity to develop more integrated and timely volcanological interpretations.

None of the above should be read to imply that HVO is simply looking at data that are automatically collected and piped into our computers. Important keys to eventually understanding what happened on March 19, as well as what we might reasonably expect to follow at Halemaumau, come from field sampling of both the gaseous and the solid emissions spewed from the vent.

Car traverses in the caldera are driven at least once per day when winds allow measurement of the gas composition of the Halemaumau plume. Also, once per day, ash and lava samples are carefully and systematically retrieved from numerous ash collectors placed on the caldera floor. Assessments of both the amount and compositions of these samples provide insights into what lies beneath the caldera and why Kīlauea is behaving as we observe.

While HVO's monitoring networks are already dense around Halemaumau, HVO scientists have deployed additional instruments to complement the permanent instrumentation. A continuously operating gravimeter is recording signals that might reflect increases or decreases in the magma mass stored beneath Kīlauea caldera, and additional GPS receivers near Halemaumau are intended to improve resolution of smaller-scale ground surface movements around the vent. Groups of borrowed portable seismometers were temporarily deployed in small antenna-like arrays to help locate ultra-small earthquakes beneath the new vent.

As Halemaumau continues to entertain and intrigue, we maintain our enhanced observing. With contingency and continuity-of-operations plans in place, we expect that if Halemaumau should explode more violently; we will be doing much of the same - only not so close to ground-zero. Please continue to share our web postings at: http://hvo.wr.usgs.gov.

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### Volcano Activity Update

Kīlauea summit and Puu Oo continued to deflate after completing two DI tilt events this past week. Sulfur dioxide emission rates and seismic tremor levels have remained elevated at several times background levels. Earthquakes were located primarily beneath Halemaumau Crater and the adjacent areas, the southwest rift zone, and the south flank faults.

Lava from the 2007 Thanksgiving Eve Breakout (TEB) flow, erupting from fissure D of the July 21 eruption, continues to flow through what remains of the Royal Gardens subdivision and across the coastal plain. On Wednesday, March 5, the flow entered the ocean (Waikupanaha entry) in the vicinity of Kapaahu. The Waikupanaha delta has since grown to a width of about 1,000 m (3,280 ft) and has multiple entry points. On March 15, another branch of the flow reached the ocean (Ki entry) farther to the east, within a few hundred meters of the lava viewing area. During the past week, lava supply to the Ki entry ceased, though the Waikupanaha entries remain fully active.

The public should be aware that the ocean entry areas could collapse at any time, potentially generating large explosions in the process. The steam clouds rising from the entry areas are highly acidic and laced with glass particles. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves suddenly generated during delta collapse; these beaches should be avoided. Check the County of Hawaii Civil Defense website for information on public access to the coastal plain and ocean entry.

The surface flows active last week on TEB shield complex were stalled by Saturday, April 19, and no other surface flows in the shield complex area have been observed this week. Throughout the past week small breakouts from the tube system have been observed in the Royal Gardens subdivision.

No incandescence was observed at night in Puu Oo in the past week, though minor incandescence has been sporadically present throughout the past few months. As in years past, Puu Oo likely is serving as a large chimney, beneath which lava is briefly stored and substantially degassed on its way to the eruption site.

On March 11, a new fumarole appeared low on the southeast wall of Halemaumau Crater, within Kīlauea's summit caldera. The new vent is located directly beneath the Halemaumau Overlook about 70 m (230 ft) down. At 2:58 a.m. on March 19, a small explosion occurred from this fumarole. The explosion scattered rock debris over an area of about 75 acres, covering a narrow section of Crater Rim Drive, the entire Halemaumau parking area, and the trail leading to the overlook. The overlook was damaged by rocks that reached up to 90 cm (3 ft) across. No lava was erupted as part of the explosion, suggesting that the activity was driven by hydrothermal or gas sources. On April 9 another small explosion occurred, depositing dense blocks and particles of fresh lava on the overlook area. Last week, another small explosion from the vent occurred at 3:57am on April 16, producing a dusting of pale-red ash west of the crater. The new explosion pit continues to vigorously vent gas and ash, with the plume alternating between brown (ash-rich) and white (ash-poor). Fresh lava spatter, Pele's tears and Pele's hair have been collected at the rim, indicating that magma resides at shallow depths in the new conduit.

Sulfur dioxide (SO2) emission rates from the summit area have been substantially elevated up to 10 times background values since early January; the emission rates for the past week have been decreasing but are still elevated. The increase in sulfur dioxide emission rates at the summit means that SO2 concentrations are much more likely to be at hazardous levels for visitor areas downwind of Halemaumau, especially during weak wind conditions or when winds blow from the south. Most people are sensitive to sulfur dioxide at these levels, especially children, individuals with asthma, chronic obstructive pulmonary disease (COPD), or other breathing problems. Stay informed about SO2 concentrations in continuously monitored areas (Jaggar Museum and Kīlauea Visitor Center) by visiting the Kīlauea Visitor Center and the web at:
One earthquake beneath Hawaii Island was reported felt within the past week. A magnitude-3.3 earthquake occurred at 7:08 p.m., and was located 10 km (6 miles) northwest of Pahala at a depth of 10 km (6 mile).