Drop in lava lake level within Halemaʻumaʻu crater and summit activity changes

By USGS/HVO

KÄ«lauea Volcano’s summit lava lake continued to drop today (May 15, 2015). Measurements of the lake surface late Friday afternoon (May 15) showed that it was 62 m (203 ft) below the top of the newly-created vent rim, a ridge (or levee) of solidified lava about 8 m (26 ft) thick that accumulated on top of the HalemaÊ»umaÊ»u Crater floor from multiple overflows of the vent during the past two weeks. Photo taken Friday, May 15, 2015 courtesy of USGS/HVO

The lava lake in the Overlook crater (summit vent) overflowed its rim beginning April 28, sending many short flows across the floor of Halemaʻumaʻu Crater. By May 8, these overflows and spatter from the rising lava lake had built a ridge (or levee) of solidified lava around the vent rim to a height of about 8 m (26 ft) above the floor of Halemaʻumaʻu Crater, creating a “perched lava lake.” On May 9, the lava lake level began to drop, and, as of Friday morning (May 15), the lake surface was about 50 m (165 ft) lower than the newly created vent rim.

The abrupt lowering of the lava lake level was accompanied by changes in summit deformation and seismicity. As the lava lake dropped, the inflationary trend previously observed in the summit area changed to a deflationary trend centered near Halema‘uma‘u Crater. On May 13, the focus of deformation changed to the southern part of Kīlauea’s summit caldera and upper Southwest Rift Zone, where rapid and localized inflationary tilt was recorded.

This change in deformation was accompanied by a shift in the focus of earthquake activity from Kīlauea’s summit, upper East Rift Zone (ERZ), and upper Southwest Rift Zone (SWRZ) to the southern part of Kīlauea’s caldera and Upper SWRZ. Of the many hundreds of earthquakes that have occurred in the SWRZ over the past 2 days, most have been small (less than magnitude-2) and shallow (less than 4 km [2.5 mi] deep). As of noon on May 15, earthquakes over the past 12 hours were occurring every couple of minutes, the highest rate recorded thus far, including this morning’s magnitude-3.2 quake at 08:37 a.m., HST, and magnitude-3.0 quake at 10:52 a.m., HST.

During this period of elevated summit activity, there has been no obvious change in the eruption rate of lava from the Puʻu ʻŌʻō vent on Kīlauea’s East Rift Zone. Few earthquakes have occurred in the upper ERZ over the past few days.

What We Can Expect

HVO webcams captured a short-lived dusty-brown plume generated by a small rock fall from the summit vent wall at 3:24 p.m., HST, Friday afternoon (May 15). Photo taken Friday, May 15, 2015 courtesy of USGS/HVO

These recent changes at the summit of KÄ«lauea suggest that magma has moved into a shallow area beneath the southern part of the caldera and upper Southwest Rift Zone.

It is not possible to predict the exact outcome of this activity, but we identify three possible scenarios that could play out in the coming days to weeks:

1. Magma continues to accumulate in the southern part of Kīlauea’s summit caldera and upper SWRZ at shallow depths, but then stops with no eruption.
2. Magma continues to accumulate in the southern part of the caldera at shallow depths and leads to a rapid intrusion into the Southwest Rift Zone. Such an intrusion could remain within the rift zone or erupt along the rift zone. A rift zone intrusion would be indicated by a swarm of shallow earthquakes, seismic tremor, and large, rapid changes in the deformation of the ground surface.
3. Magma continues to accumulate in the southern part of the caldera, rises toward the surface, and erupts in the upper SWRZ and/or in the caldera. With this scenario, we would expect to see even stronger earthquake activity and/or seismic tremor in the southern part of the caldera, as well as ground cracks.

However, the overall evolution of unrest in Kīlauea’s summit area and upper rift zones in the coming weeks to months is uncertain. The magma storage system within Kīlauea is highly pressurized at this time, and future changes in the location of unrest—and the potential for eruption—could unfold quickly (in days to hours).

What We Are Doing

HVO continues to closely monitor Kīlauea Volcano, watching for any signs of unrest that may precede a new outbreak of lava or changes in activity at Puʻu ʻŌʻō or the summit. HVO is in frequent communication with Hawai‘i Volcanoes National Park and Hawai‘i County Civil Defense to keep them apprised of the activity.

HVO will continue to post daily eruption updates on our web site, along with photos, videos, and maps as they are available at: http://hvo.wr.usgs.gov/activity/kilaueastatus.php.

You can also receive daily KÄ«lauea eruption updates via email by subscribing to the Volcano Notification System at: http://volcanoes.usgs.gov/vns/