VOLCANO WATCH: Halema’uma’u Crater Eruption Turns Seven

While Kīlauea Volcano’s East Rift Zone eruption at Pu’u ‘Ō’ō has been making headlines with the June 27 lava flow and its hazards, Kīlauea’s summit eruption within Halema’uma’u Crater has steadily continued in the absence of much press. However, the lack of media attention does not reflect on the eruption’s remarkable nature.

Kīlauea’s ongoing summit eruption began on March 19, 2008, after several months of increasing seismic tremor and gas emissions. A small “throat clearing” explosion opened a new crater (informally called the Overlook crater, because it is located immediately below the former National Park visitor overlook) on the wall of Halema’uma’u Crater. During 2008–2009, lava was only occasionally seen deep within this crater and was often masked by thick volcanic fume.  In February 2010, however, lava rose within the Overlook crater and established a large lava lake that has persisted to today.

When the Overlook crater first opened, it was about 35 m (115 ft) wide, but today, it is 170 m by 220 m (560 ft by 720 ft) in size. This enlargement is the result of frequent collapses of the crater walls, some of which have dropped rocks directly into the lava lake, triggering small explosions of lava spatter and gas.

Unlike the East Rift Zone eruption which sends lava flows out onto the slopes of Kīlauea, the summit eruption emits primarily gas, along with a tiny amount of ash and fine particles (for example, Pele’s hair). To date, the lava within the summit vent has not flowed out of the Overlook crater. Instead, lava rises into the lake, releases gas and cools, and then sinks back into the magmatic system in a process called “magmatic convection.”

This containment within the crater lowers the risk posed by the lava itself, but the summit eruption creates a different kind of hazard that has a much farther reach than any lava flow. The continuous gas emissions create volcanic air pollution, commonly called “vog,” which affects communities and agriculture in downwind areas, sometimes statewide. Vog is a respiratory irritant that can cause coughing, sore throats, and headaches in otherwise healthy individuals, and can aggravate symptoms in people with pre-existing ailments, such as asthma and chronic obstructive pulmonary disease. The agricultural industry, particularly in the Ka’ū District on the Island of Hawai’i, has been hit hard by vog, which has damaged crops and corroded fences and other metal infrastructure.

Geologically, the Kīlauea summit eruption stands out for the size of the lava lake it has created.  The lava lake in Halema’uma’u is most likely the second-largest lava lake on Earth, exceeded only by the lava lake in Nyiragongo Volcano in the Democratic Republic of the Congo. There are a few other—and much smaller—lava lakes on Earth, but the Halema’uma’u and Nyiragongo lava lakes are in a class of their own.

The expansive size of the lava lake in Halema’uma’u also translates to copious amounts of emitted heat. A recent study by University of Hawai’i Mānoa researchers used satellite thermal images to calculate heat output from many of the Earth’s active volcanoes over the past 15 years, and Kīlauea—counting the summit and East Rift Zone eruptions together—was at the top of the list. The researchers state that Kīlauea’s top rank in heat output justifies its unofficial title as the most active volcano on Earth.

It’s not clear how long Kīlauea’s summit eruption will last, but recent monitoring indicators show no signs of it slowing down—or speeding up. Overall, the eruption has been characterized by a remarkable degree of steadiness. Halema’uma’u Crater hosted a nearly continuous lava lake for at least 100 years (first written accounts are from the early 1800s) through the early 1900s, a testament to the potential for long-lasting eruptions at the summit of Kīlauea.

Is it possible that Kīlauea Volcano’s current summit eruption will persist for decades, as it did a century ago? No one knows for sure, but if it does, we will all have to continue adapting to the effects of another long-term eruption.

Kīlauea activity update

Kīlauea’s East Rift Zone lava flow fed breakouts across the leading 3 km (2 mi) of the flow, but the leading tip of the flow remained stalled 500 m (550 yd) upslope from Highway 130. Breakouts were also active west of Kaohe Homesteads and on the north flank of Puʻu ʻŌʻō. A new breakout began this past week near the forested cone of Kahaualeʻa, about 2 km (1.2 mi) northeast of Puʻu ʻŌʻō.

The summit lava lake level tracked summit deformation, rising about 25 m (80 ft) over the past week with inflation. The lake level was 48 m (160 ft) below the rim of the Overlook crater as of Thursday, March 12.

One earthquake was reported felt on the Island of Hawai’i this past week.  On Friday, March 6, at 12:22 a.m., a magnitude 3.7 earthquake occurred 5 km (3 mi) northeast of Kailua-Kona at a depth of 14 km (9 mi).

Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey`s Hawaiian Volcano Observatory.