By USGS – Hawaiian Volcano Observatory

It wasn’t too long ago that tour buses shuttled hundreds of visitors a day to the Halema`uma`u parking lot. A short trail led the visitors to the Halema`uma`u Overlook, where they could look out over Halema`uma`u Crater and imagine its former eruptions and the famous lava lake from the 1800s and early 1900s. The screech of a koa`e kea (white-tailed tropic bird) nesting in the crater walls, or shuffling of other visitors, or a gust of wind, might be the only interruption to the tranquil view.

Things are much different now at Halema`uma`u. The visitor overlook – now closed to the public – has been destroyed. The ground around the overlook is littered with blocks and bits of spatter, a testament to recent explosive events. Gusts of wind whip a plume carrying suffocating concentrations of volcanic gas. A low, constant rumble and occasional crashing rockfalls broadcast that a lava lake is again active in Halema`uma`u.

The current summit eruption began on March 19, 2008, with an explosive event that created a new opening about 35 m (115 ft) wide, which we call the Overlook crater. During the first six months of the eruption, lava was deep and rarely visible. The Overlook crater produced a handful of small, explosive events that threw rocks and spatter several hundred meters (yards) away from the crater. Throughout 2009, the lava remained deep within the enlarging crater, often spattering from small sources or feeding brief lava ponds.

The eruption changed in February 2010 when a continuous lava lake appeared. This lava lake has persisted to today with one brief interruption in March of 2011. The Overlook crater has enlarged significantly over time and is now 160 m (520 ft) wide. Over the last year, the lava has crept higher and has recently been about 30-50 m (100-160 ft) below the rim of the Overlook crater. For all its change, the one consistent feature of the eruption is the continuous gas plume, which injects large amounts of sulfur dioxide into the air.

The eruption has had both positive and negative impacts on the Big Island. On the positive side, the nighttime glow is an entrancing reminder of Pele’s presence, and a big draw for visitors to Hawai`i Volcanoes National Park. The continuous lava lake provides one of the world’s best natural laboratories for volcanic activity, and it has improved our understanding of lava lake behavior and Kilauea’s magmatic system.

HVO scientists and collaborators have learned many new things about the vent, and a few deserve mention here. First, detailed video observations have shown that the small explosions that occur sporadically are triggered by rockfalls that impact the lava lake; this is a new type of explosive activity in the field of volcanology. Second, degassing at the summit appears to affect the magma traveling to the east rift zone vent on Pu`u `O`o, and contributes to the reduced gas emissions released there. Third, geophysical data collected near the vent have confirmed that the lava lake density is very low (as hypothesized in the early 1900s), presumably because of its high gas content; this has broad implications for understanding lava lake circulation.

But the eruption has also created some serious hardships for island residents. Volcanic gas emissions have severely impacted air quality in downwind communities, particularly those in Ka`u and south Kona, and have affected the quality of life for many residents. Agriculture and ranching, major parts of Big Island communities and the local economy, have been hit hard. The U.S. Department of Agriculture declared the Big Island a disaster area due to losses over the last several years.

What is the outlook for the summit eruption? Currently there are no signs thus the eruption is slowing down or ramping up. Now entering its sixth year, this prolonged activity harkens back to the decades of lava lake activity in Halema`uma`u during the 1800s and early 1900s. This history suggests that the current eruption may have the potential to last for years to come but, at this point, there is no way to know with certainty.