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2018 lower East Rift Zone Eruption and Summit Collapse

In 2018, Kīlauea’s long-lived Pu‘u‘ō‘ō eruption, on the middle East Rift Zone, and decade-old summit lava lake eruption ended. A large lower East Rift Zone eruption partially drained the summit magma reservoir, which caused portions of the unsupported summit caldera floor to collapse. 

Kīlauea 2018 lower East Rift Zone Eruption and Summit Collapse

In 2018, Kīlauea’s long-lived Pu‘u‘ō‘ō eruption, on the middle East Rift Zone, and decade-old summit lava lake eruption ended. A large lower East Rift Zone eruption partially drained the summit magma reservoir, which caused portions of the unsupported summit caldera floor to collapse. The event was significant for being the largest lower East Rift Zone eruption and summit collapse in at least 200 years; it was also sadly the most destructive eruption in Hawaii over the same time period.

Collapse of Pu‘u‘ō‘ō and dike migration down Kīlauea East Rift Zone

plume of reddish-brown ash skyward
With each large earthquake, ground shaking causes additional collapse within the Pu‘u ‘Ō‘ō crater, sending a plume of reddish-brown ash skyward. The size and vigor of a plume depends on the size of the earthquake and subsequent collapse. This roiling ash plume followed the magnitude-6.9 earthquake on May 4. Much of the rock within the crater is rust in color, which is a result of heavy alteration by acidic volcanic gases. When the rock is pulverized by a collapse event, the resulting ash plume is pink to reddish-brown ash plume.

Increased pressurization of Kīlauea’s magmatic system, indicated by high lava lake levels at the summit and increased rates of ground tilt, likely enabled magma to intrude past Pu‘u‘ō‘ō, a vent that had been erupting nearly continuously on Kīlauea’s middle East Rift Zone since 1983. Pu‘u‘ō‘ō shield collapsed on April 30, 2018, forming a crater; this reflected a sub-surface change that allowed a dike body of magma to move below ground towards the lower East Rift Zone.

Progression of the dike down-rift was reflected in the similar spatial progression of earthquake activity, and on May 3, 2018, lava broke out onto the surface within Leilani Estates, a residential subdivision on the lower East Rift Zone of Kīlauea. Early in the eruptive sequence, several fissure vents opened that were slightly offset from the rift zone, where they began erupting spatter and sticky, viscous, lava flows that did not travel far from the vents they were being erupted from. Geochemical analyses indicated that this initially erupted lava had been stored and cooling beneath the surface of the rift zone for decades.

A magnitude 6.9 earthquake occurred on May 4, 2018 and dilated the rift zone by approximately 5 m (16 ft). The earthquake was likely caused by pressure induced by the dike continuing to intrude into the lower East Rift Zone.

eruption in Leilani Estates in the lower Puna District
An intrusion of magma into Kīlauea Volcano's lower East Rift Zone resulted in an eruption in Leilani Estates in the lower Puna District on the Island of Hawai‘i. The first four fissures to erupt in the subdivision are shown here on May 4, emitting copious amounts of hazardous sulfur dioxide gas. Pu‘u ‘Ō‘ō (top center), which is about 20 km (12.4 mi) uprift of Leilani Estates, can be seen on the far horizon (top center). As of May 6, at least 10 fissures have erupted in the subdivision.
Kilauea summit lava lake
The summit lava lake has dropped significantly over the past few days, and, as of the evening of 5/6/18, was roughly 220m below the crater rim. This very wide angle camera view captures the entire north portion of the Overlook crater.

As the dike progressed into the lower East Rift Zone, and during the initial days of the eruption there, the lava lake that had been active within Halema‘uma‘u crater at Kīlauea’s summit began to drain. By May 10, 2018, the lava lake had dropped out of view, and rockfalls were common in the summit vent area, generating small ashy plumes. On May 16, the first of a dozen minor explosive events occurred, with a plume consisting of ash-sized fragments of the crater walls (no fresh lava was present) and small crater-wall blocks; slightly elevated summit sulfur dioxide (SO2) emissions accompanied these events. The USGS Hawaiian Volcano Observatory (HVO) abandoned observatory buildings near Kīlauea summit, as frequent earthquakes in the summit region began to damage the structures.

A dark ash plume rising from a crater
At 1:38 p.m. HST, another dark ash plume rose from the Overlook crater. During a flight earlier today by the Civil Air Patrol, the height of the ash plumes near the crater rose to more than 3 km (9,800 ft) above sea level, and downwind the plumes continued to rise to about 3.5 km (11,500 ft) above sea level.

Change in eruption dynamics and focus on fissure 8

In mid-May of 2018, the character of the eruption on the lower East Rift Zone changed. Hotter and more fluid magma began to erupt from multiple vents, which allowed lava flows to travel faster and farther; geochemical analyses indicated that this change was facilitated by the arrival of “fresher” magma from the summit reservoir. These larger lava flows generally moved in a southeast direction, with lava flows first crossing a highway and entering the ocean the following day—May 19, 2018—near Mackenzie State Recreational area.

Aerial of lava flow
Channelized lava emerges from the elongated fissure 16-20 (in the upper right). Photo taken May 19, 2018, at 8:18 AM HST.

In late May, larger areas of the summit began to subside and collapse incrementally as the lower East Rift Zone eruption continued to slowly drain Kīlauea’s summit magma chamber. The collapses and associated activity progressed cyclically; earthquakes in the summit region would increase until the unsupported floor of the caldera dropped—in a piston-like manner—down by several meters (several yards), after which earthquake activity would diminish. Over the next day or so, the earthquake activity would progressively increase again. Up to 700 earthquakes equal to or greater than magnitude 4 occurred between each summit collapse event, which culminated in a near-daily magnitude 5.2–5.4 earthquake.

Aerial photo of summit
Aerial view of Kīlauea Volcano's summit caldera and an ash plume billowing from Halema‘uma‘u, a crater within the caldera. The USGS–Hawaiian Volcano Observatory and Hawai‘i Volcanoes National Park's Jaggar Museum are visible on the caldera rim (center right); Kīlauea Military Camp can be seen in the lower right. Photo courtesy of the Civil Air Patrol.

On May 27, 2018, activity returned to one of the fissure vents that had been active earlier in the eruption—fissure 8. By the following day, eruptive activity became focused at fissure 8, where an 80-m-high (260 ft) lava fountain rapidly produced a tephra cone. A channelized lava flow from fissure 8 travelled in a northeast direction to enter the ocean at Kapoho Bay on June 3, 2018.

Ocean entry at Kapoho Bay
Video from helicopter overflight of Kīlauea Volcano's lower East Rift Zone on June 4, 2018, shows lava from fissure 8 entering the ocean at Kapoho Bay. View to the north.

Near the coast, the fissure 8 lava flow field expanded, entering the ocean in numerous locations, and forming a large lava delta. Eventually, the direction of the channelized flow shifted southward, around the west side of Kapoho Crater, and small ocean entries proceeded southwest along the coast approaching Pohoiki Bay.

Kīlauea’s summit continued to incrementally collapse as the lower East Rift Zone eruption slowly siphoned magma from the summit storage system. In total, 62 collapse events occurred.  Several hours after the floor of Kīlauea’s summit experienced a collapse, the lava eruption rate at fissure 8 in the lower East Rift Zone would surge, reflecting increased pressurization of Kīlauea’s magma system as a result of the summit collapse event.

image related to volcanoes. See description
Then and now. It has proven difficult to exactly match past and present views of Kīlauea's summit to show the dramatic changes in the volcanic landscape, but here's our latest attempt. At left is a photo taken on November 28, 2008, with a distinct gas plume rising from the vent that had opened within Halema‘uma‘u about eight months earlier. At right is a photo taken on August 1, 2018, to approximate the 2008 view for comparison.

The last collapse event occurred at Kīlauea’s summit on August 2, 2018, and, on August 4, 2018, lava eruption rates and SO2 emission rates at fissure 8 in the lower East Rift Zone greatly decreased. Lava was intermittently visible within the fissure 8 cone over the next month, and ocean entries slowed and eventually ceased by August 21, 2018. Active lava was last visible within fissure 8 on September 5, 2018.

Impacts, significance, and interpretations

Locally, the destruction caused by Kīlauea’s 2018 lower East Rift Zone eruption was unprecedented in modern history. An area of 35.5 square kilometers (over 8,700 acres) was covered with lava, which includes the addition of 875 acres of new land created near the eastern extent of the Island of Hawai‘i. Residents were displaced as lava covered over 700 structures and 48 kilometers (30 miles) of road; other uncovered properties in the lower East Rift Zone became inaccessible as lava flows blocked access.

Much of the State of Hawaii, and areas as far as Guam, were also impacted by vog—volcanic air pollution caused by interaction of the atmosphere with nearly 200,000 metric tons of SO2 being emitted each day of the 2018 lower East Rift Zone eruption.  These emission rates are the largest ever measured on Kīlauea, representing a total of 10 Mt (megatonnes, or millions of tonnes) of SO2 between May and early August 2018.

Edge of the Kīlauea vog plume near Waikoloa Village
Edge of the Kīlauea vog plume near Waikoloa Village on the west side of Hawai‘i Island as it is blown by trade winds across the island and toward the Pacific Ocean. For more information on sulfur dioxide emissions and vog, see

After Kīlauea summit lava lake drained and the summit began to collapse in 2018, concern grew regarding the potential for violent explosions, as had occurred during a similar (but smaller) sequence of events at Kīlauea summit in 1924. However, the 2018 events proceeded passively at the summit, with none of the anticipated violent explosions occurring. Whereas models for the 1924 events suggested that interaction of hot rocks and groundwater incited explosions, the primarily lithic-ash (composed of older rock material, as opposed to fresh lava) plumes and slightly increased SO2 emissions during the 2018 events suggested that magmatic gas was a driver.

At Kīlauea summit, infrastructure within Hawai‘i Volcanoes National Park was damaged by the more than 60,000 earthquakes that accompanied the summit collapse events. In total, the summit caldera deepened by more than 500 meters (1600 feet) and the volume of summit collapse approximately half the volume of lava erupted in the lower East Rift Zone—approximately 0.8 cubic kilometers (0.2 cubic miles) of summit collapse compared to 1.5 cubic kilometer (0.4 cubic miles) of lava erupted.

The large volume of Kīlauea summit collapse and lower East Rift Zone eruption in 2018 was likely facilitated by the relatively low elevation of the 2018 vents, over 900 meters (3,000 feet) lower than the summit. Once a pathway was established for magma to be transported from the summit to fissure 8, named “Ahu‘ailā‘au” after the eruption, hydrostatic (magmastatic) pressure enabled the eruption to continue at a high rate not observed previously on Kīlauea.

routine inspection of a UAS system prior to a flight
Two U.S. Geological Survey Unmanned Aircraft Systems (UAS) pilots perform a routine inspection of a UAS system prior to a flight at the summit of Kīlauea Volcano in June 2018. The UAS for this particular flight was outfitted with a multi-gas sensor to identify any new degassing sources within the collapsing summit caldera. All UAS flights inside Hawai‘i Volcanoes National Park were conducted with explicit permission of the National Park Service.

Modern monitoring techniques were applied to Kīlauea’s 2018 events and enabled efficient hazard assessment. Changes in chemistry of lava eruption from Kīlauea’s lower East Rift Zone in 2018 were measured in near real-time and heralded changes in eruption style and associated hazards. Detailed simultaneous monitoring of the summit and East Rift Zone eruption site demonstrated the hydraulic connection between the two; monitoring crews were able to anticipate increased lower East Rift Zone eruption site hazards associated with lava surges caused by summit collapse events. New monitoring techniques were developed, such as use of Unoccupied Aircraft Systems (UAS) for monitoring vent and lava flow dynamics and measuring volcanic gas emissions; digital elevation models were updated during the eruption to more accurately forecast lava flow paths. This comprehensive monitoring regime advanced knowledge of Kīlauea’s magma plumbing system and eruption dynamics and allowed for better hazard assessments.

Following the summit collapse and lower East Rift Zone eruption of Kīlauea in 2018, the volcano entered a brief period of quiescence. Water that appeared in the base of the collapsed area in July 2019 grew into a large lake that was monitored with many of the techniques developed during Kīlauea’s 2008–2018 summit lava lake and 2018 eruption. In December 2020, an eruption began within Halema‘uma‘u at the summit. The erupting lava quickly vaporized the water lake and replaced it with a larger lava lake. The lava lake filled 229 meters (751 feet) of the 2018 collapsed area and was active through May 2021.

Resources Relating to Kīlauea's 2018 Activity

Kīlauea 2018 Eruption Data

Color photograph showing the summit of Kīlauea Volcano.
USGS scientists captured this stunning aerial photo of Halemaumau and part of the Kīlauea caldera floor during a helicopter overflight of Kīlauea's summit on July 13, 2018. In the lower third of the image, you can see the buildings that housed the USGS Hawaiian Volcano Observatory and Hawai‘i Volcanoes National Park's Jaggar Museum, the museum parking area, and a section of the Park's Crater Rim Drive. Although recent summit explosions have produced little ash, the drab gray landscape is a result of multiple thin layers of ash that have blanketed the summit area during the ongoing explosions. (Public domain.)

Relevant Publications

Maps, Videos, and Photos

See the table summarizing Kīlauea activity over the past ~200 years here.