In early September 2016, U.S. Geological Survey Hawaiian Volcano Observatory monitoring instruments on Kīlauea began recording increased rates of inflation and slightly elevated shallow earthquake activity. These changes indicate a higher rate of magma accumulation within the volcano’s summit magma reservoir.

This magma accumulation is also reflected—quite visibly for visitors at the Jaggar Museum Overlook in Hawaiʻi Volcanoes National Park—by periodic, and sometimes rapid, rises of the lava lake within Halemaʻumaʻu Crater. When the lake level is high, vigorous spattering on the lake surface creates a dazzling display, especially after dark, when the incandescent lava lights up the night sky.

Long-time volcano watchers have likely noticed that Kīlauea’s summit lava lake rises and falls in concert with summit inflation and deflation. During the last half of 2015, the lava lake level generally fluctuated between about 131 and 230 feet below the rim of the vent on Halemaʻumaʻu Crater’s floor.

Throughout 2016, the lava lake level has typically varied between 66 and 131 feet below the vent rim. That is, until early September, when the increased rate of inflation resulted in higher lake levels.

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On Sept. 10, the summit lava lake rose to within 16 feet of the vent rim, but dropped the next day with the onset of summit deflation. Since then (as of Sept. 22), the lava lake level has fluctuated between 33 and 92 feet below the rim, rising and falling with periods of inflation and deflation—and thrilling Park visitors who happen to see the lake during one of its high stands.

Like those visitors, HVO staff enjoy the beauty of Kīlauea’s lava lake activity. But, as scientists, we also ponder what it means.

It’s impossible to know the exact outcome(s) of a pressurized magma reservoir. We have, however, identified possible scenarios based on recent observations and past similar events.

For example, given long-term trends and current conditions at Kīlauea, we expect summit inflation and elevated earthquake activity to continue. With inflation, we also anticipate periodic high lava lake levels—possibly with lava overflowing the vent rim and spreading across the floor of Halemaʻumaʻu Crater, as happened in April-May 2015.

Intermittent rockfalls in the summit vent are also expected. Rocks falling from the vent walls and into the lava lake can initiate explosions that send spatter (clots of molten lava), solid rock fragments, and bits of volcanic glass (ash, Pele’s hair, Pele’s tears) flying into the air. During past explosions, spatter and solid rocks up to a yard or more in size have been thrown onto the rim of Halemaʻumaʻu Crater. These hazardous explosions occur suddenly and without warning—as recently as Sept. 19—one reason why Halemaʻumaʻu has been closed to the public since February 2008.

If a lava lake explosion occurs under southerly wind conditions, tiny particles of volcanic glass and pulverized rock could be blown toward Jaggar Museum and other viewing areas. This could result in a “dusting” of Pele’s hair and gritty ash at park overlooks.

The summit vent continues to emit sulfur dioxide and other volcanic gases that produce poor air quality downwind from the lava lake. But closer to the vent, along the Halemaʻumaʻu Crater rim, gas concentrations are potentially life-threatening—the main reason why this area remains closed to the public.

Inflation of Kīlauea’s summit reservoir increases the chance of magma intruding into the volcano’s south caldera or upper rift zones. Such an intrusion would likely result in a rapid drop in the summit lava lake, and could cause new breakouts of lava, like the 2011 Kamoamoa fissure eruption. If the magma supplied to Pu‘u ‘Ō‘ō increases, changes in the 61g lava flow and Kamokuna ocean entry could occur.

HVO scientists closely watch Kīlauea for any signs of an intrusion—changes in deformation and seismicity—that might precede a new breakout of lava. HVO’s monitoring instruments are programmed to rapidly alert us—day and night—to sudden changes on the volcano.

It’s an exciting and interesting time on Kīlauea—for both the public and the scientists who study the volcano.

Volcano Activity Updates

Kīlauea continues to erupt at its summit and East Rift Zone. As of Sept. 22, the summit lava lake level varied between 33 and 92 feet below the vent rim within Halema‘uma‘u Crater. The 61g lava flow continued to enter the ocean near Kamokuna, with active breakouts about 1.2 miles inland from the ocean entry. The lava flow does not pose an immediate threat to nearby communities.

Mauna Loa is not erupting. Seismicity remains elevated relative to the long-term background rate, with small earthquakes occurring mostly in the volcano’s south caldera and upper Southwest Rift Zone at depths less than 3 miles. Global Positioning System (GPS) measurements show deformation related to inflation of a magma reservoir beneath the summit and upper Southwest Rift Zone, with inflation occurring mainly in the southwestern part of the volcano’s magma storage complex.

No earthquakes were reported felt on the Island of Hawaiʻi this past week.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

Call for summary updates at (808) 967-8862 (Kīlauea) or (808) 967-8866 (Mauna Loa); email questions to [email protected].