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Frequently Asked Questions about Kīlauea's Summit Eruption

Kīlauea Summit Eruption Frequently Asked Questions

Color photo of lava lake
Scientists monitor an eruption in Kīlauea Volcano's summit caldera, Island of Hawai‘i. This photo, from the south rim of Halema‘uma‘u crater and looking north, shows the volcanic gas plume heading west. USGS photo by M. Patrick on Dec. 23. (Public domain.)

What triggered these eruptions? Are they major or minor events? 

This is an exciting time on Kīlauea Volcano because lava has returned to the summit following the 2018 summit collapse. Let’s review what Kīlauea’s monitoring data has shown since the 2018 events: 

Kīlauea Volcano had maintained a low level of non-eruptive unrest since the end of the 2018 lower East Rift Zone eruption and summit collapse, which deepened Halemaʻumaʻu crater by over 500 meters (1640 feet).  Two months after the end of the 2018 eruption, the HVO monitoring network detected Deflation-Inflation events (DI-events) indicative that the shallow Halemaʻumaʻu magma reservoir, located approximately 1.6 km (1 mile) under Kīlauea caldera, still contained significant amounts of magma.  Several months after that, in March of 2019, the summit began to steadily inflate.  Beginning in September 2020, increased rates of uplift were observed by Global Positioning System (GPS) stations in Kīlauea’s upper East Rift Zone and over the past month were observed in Kīlauea’s summit region. 

On December 2, 2020, GPS stations and tiltmeters recorded a ground deformation event at Kīlauea’s summit indicative of a small dike intrusion of magma under the southern part of Kīlauea caldera. Following the intrusion, seismometers detected a notable increase in occurrence and duration of long-period seismic signals beneath Kīlauea’s summit, which are attributed to magmatic activity, beginning on December 17, 2020. The eruption began as fissures on the walls and lowest down-dropped block within Halemaʻumaʻu on December 20 at approximately 9:30 p.m. HST.  Eventually, activity became focused at a vent on the west wall of Halemaʻumaʻu. By May, the eruption had filled Halemaʻumaʻu crater with 223 meters/732 ft of lava (equal to an elevation of approximately 741 meters/2431 ft above sea level); the last activity on the lava lake surface was observed on May 23, 2021. 

After the December 2020-May 2021 Halemaʻumaʻu eruption ended, Kīlauea summit region continued to slowly inflate. In August 2021, increased earthquake activity and patterns of ground deformation indicated that another intrusion event was occurring; this time, the magma was moving into an area south of Kīlauea caldera. However, no eruption occurred, and the shallow Halemaʻumaʻu magma reservoir continued to measure inflation. On September 29, 2021, another series of vents opened in the floor and walls of Halemaʻumaʻu crater, generating another lava lake. This activity is ongoing, please see the eruption webpage for more information. 

This pattern of collapse (such as occurred in 2018) and eruption is part of the cyclic behavior that Kīlauea Volcano has shown many times over the past 200 hundred years. You can read more about it here: 

Color photograph of eruption
The eruption at Kīlauea Volcano's summit within Halema‘uma‘u crater. This photo, taken at approximately 2:43 p.m. HST on December 22, shows the two fissures active on the crater wall that continue to feed a growing lava lake. USGS photo by L. DeSmither. (Public domain.)


Will there be explosions (because of water)? 

Color thermal images of lava lake
A comparison of two thermal images from the F1cam thermal webcam located on the rim of Halema‘uma‘u crater, at the summit of Kīlauea volcano. These two images were taken 48 hours apart. The left image from December 20 at 8:22 a.m. HST, shows the water lake that was in the bottom of the crater—approximately 13 hours before the start of the summit eruption at Kīlauea. The image on the right was taken today at 8:22 a.m. HST, December 22. The water lake had been replaced by a lake of lava that was fed by multiple fissure that opened on the Halema‘uma‘u crater wall. Note the difference in temperature scales (degrees Celsius) between the two images. (Public domain.)


Since the water lake boiled away in the initial stages of the eruption that began in December 2020, it is less likely that there will be water-driven explosive activity at  Kīlauea’s summit. Though geophysical studies show that a large area underlying Kīlauea’s summit contains groundwater, most Kīlauea summit eruptions over the past 200 years have occurred without explosive activity. HVO is monitoring the situation closely for any indications of a change in activity type.  

What do we know about these lava lakes? 

The bottom of Halemaʻumaʻu crater at Kīlauea summit is filling with lava as these eruptions occur. The situation remains dynamic and is monitored 24-hours a day. On January 8, 2021, a novel laser rangefinder was stationed at Kīlauea volcano's summit. The fixed instrument continuously measures the distance to a location on the western lava lake surface, and telemeters data to HVO in real time. HVO also maintains visual and thermal webcameras that monitor the summit region, in addition to an extensive monitoring network of seismic and ground deformation instruments. 

Color thermal images of lava lake
This comparison shows thermal images taken during USGS Hawaiian Volcano Observatory helicopter overflights. The main difference in this 24 hour period is the significant rise and infilling of the lava lake within Halema‘uma‘u crater at Kīlauea summit. On December 21, the lake depth was measured at approximately 130 yards. USGS images by M. Patrick. (Public domain.)


Does this activity mean the LERZ will erupt again? 

The recent eruptive activity at Kīlauea's summit is confined to Halemaʻumaʻu crater within Hawai'i Volcanoes National Park.

Data from tiltmeters and Global Positioning System (GPS) stations showed contraction in the upper portion of the East Rift Zone (an area between Kīlauea’s summit and Pu‘u ‘Ō‘ō) with the onset of the December eruption. Similar instruments in down-rift areas, including the site of the 2018 eruption remained stable and did not show motion associated with either inflation or contraction. Our interpretation is that magma from the contracting portion of the East Rift Zone moved back to the summit reservoirs, where the eruption was occurring. The signal was small and preliminary modeling showed it to be a small amount of magma returning to the summit.

Concurrently, instruments at the summit showed motions consistent with slight inflation of those reservoirs. This could have been, in part, a result of magma from the upper East Rift Zone returning to the summit area, as well as a decrease in the amount of lava erupted from the December 2020-May 2021 western fissure, and the draining of lava into the now submerged December 2020-May 2021 northern fissure vent.

While magma from the summit reservoirs drained into the East Rift Zone to feed fissure eruptions in the lower East Rift Zone in 2018, there is no seismic or deformation data to indicate any changes have occurred in Kīlauea volcano’s lower East Rift Zones. It appears that magma may have been draining back into the summit reservoir in December 2020. Since then, ground deformation motion suggests that the upper East Rift Zone—between the summit and Puʻuʻōʻo—has been steadily refilling with magma but there are no new hazards expected as a result.

Monitoring data indicates that the summit is stable, and HVO is closely watching for any changes.   

Does lava entering the crater through fissures indicate the 2008-2018 vent is blocked? 

The recent eruptions in Halema‘uma‘u have occurred from a different location than the 2008-2018 Kīlauea summit lava lake vent.  When magma migrates upwards to the surface as a dike, it does so along the path of least resistance. The stress field surrounding craters are such that crater walls are the preferred path of opening versus the crater floor. This behavior is not uncommon for Kīlauea; many previous eruptions have initiated as fissures opening on crater walls. 

Map of volcano summit activity
The recent eruption at Kīlauea Volcano's summit, within Halema‘uma‘u crater, has generated a lava lake that is being fed by two fissures. Halema‘uma‘u crater has previously been occupied by a water lake (July 2019 to December 2020) and a lava lake (2008 to 2018). The current lava lake is larger than both previous lakes; though it occupies a similar (but larger) location of the former water lake, its location is slightly more north than the former lava lake.  USGS map by M. Zoeller. (Public domain.)

Will the floor of the crater collapse like it did in 2018? 

The Kīlauea summit collapses in 2018 were preceded by several weeks of intense deflationary deformation.  HVO monitoring networks are not currently measuring deflationary motion at Kīlauea summit, and therefore another summit collapse is unlikely. 

How long before the lava lake reaches the rim of Halemaʻumaʻu? 

This question is difficult to answer because the activity within Halemaʻumaʻu remains dynamic. After the eruptions first started, the lava rose rapidly both due to the shape of the base of Halemaʻumaʻu (inverted cone) and the initially high rates of lava being erupted. After that, the rate of lava being erupted varied.

See this "Volcano Watch" article for more information: "Kīlauea’s ongoing eruption: a rising lava lake."

How can I view the eruption?

Eruptions at the summit of Kīlauea occur within Hawai’i Volcanoes National Park.  

The National Park published guidelines on “How to Safely View the New Eruption in Hawaiʻi Volcanoes National Park.” Please visit the Hawai’i Volcanoes National Park website for the most up-to-date information on viewing eruptions within the National Park:

Why are some areas within Hawai‘i Volcanoes National Park closed to the public? 

Color photograph of eruption and plume
Photo shows volcanic gases from the current eruption at Kīlauea’s summit being transported southwest into the closed area (left side of photo). This photo also shows the cracks, cliffs, and uneven ground surfaces present in the closed area of Hawai‘i Volcanoes National Park. USGS photo by K. Mulliken on 12/21/2020. (Public domain.)

Some areas within the Park are closed because of ongoing, persistent volcanic hazards that can cause serious injury or death. These hazards can include:   

  • Sulfur dioxide and other volcanic gases: Trade winds transport gases predominantly to the southwest and conditions can change rapidly. As a result, portions of the closed area within Hawai‘i Volcanoes National Park have consistently poor air quality. USGS Hawaiian Volcano Observatory (HVO) staff carry gas-detection devices, gas masks [respirators] and eye protection so that they are aware of air quality conditions at all times and are able to respond to worsening conditions.   

  • Possible explosions or ejection of hot lava: Conditions at a lava lake can be unpredictable. As the 2008-2018 lava lake demonstrated, sudden rockfall into the lava lake, for example, could potentially generate an explosion with the ejection of hot lava. HVO field crews wear high-visibility flame-resistant clothing, gloves, eye protection, and hard hats while working near the rim and maintain contact with scientists monitoring data feeds so they are alerted to sudden changes.  

  • Cracks, cliffs, and uneven ground surface: The 2018 Kīlauea summit collapse dramatically altered the landscape within the closed area, particularly near the caldera rim and Halema‘uma‘u, the location of the current eruption. Since 2018, HVO staff have studied and mapped the area and are aware of the location of unstable surfaces, hazards, and the safest areas from which to observe the current eruption. HVO field crews entering the area are equipped with Global Positioning System (GPS) units to ensure they are accessing safe locations along safe routes and are using consistent routes so as not to damage or disturb NPS resources (native plants and nēnē, for example). 

Many of these areas have been closed since 2008, when volcanic activity resulted in the creation of a lava lake (2008-2018). 

What steps do HVO and NPS staff take to be safe in hazardous areas? 

Hawaiian Volcano Observatory scientists continue to make observations and measurements of the ongoing Kīlauea summit eruption wi
Photo shows USGS HVO field crew member working in the closed area and wearing appropriate protective gear. While in the field, USGS HVO field crews maintain constant communication with HVO staff monitoring data for changes, and with the National Park Service. Constant, multi-way communications between HVO field crews, HVO monitoring staff, and NPS officials allow all parties to communicate and be aware of the volcano’s status and changes. USGS photo by M. Patrick. (Public domain.)

Kīlauea’s summit is dynamic and the situation can rapidly change, as the recent eruption demonstrates. In addition to personal protective equipment such as gas detectors, respirators, eye protection, hard hat, high visibility heat-resistant clothing, gloves, and boots, HVO field crews are in constant communication with HVO scientists watching geophysical monitoring data. If monitoring data indicate changes that could result in unstable conditions, field crews are immediately informed and can rapidly evacuate the area. HVO field crews carry InReach tracking devices, so their field positions are known at all times. HVO field crews carry radios and maintain contact with National Park Service Rangers. 

Basic safety/PPE gear that HVO staff wear/carry: heat-resistant clothing, sturdy boots, helmet, high-VIS USGS identifier, eye protection, GPS (with waypoints, tracks), phone for communication, gas mask (respirator), gas-detection device, gloves, rain gear, first aid kit, radio for communication with NPS, InReach tracking device.

Why is it necessary for USGS HVO staff to enter hazardous areas? 

person in protective gear using a spectrometer on the rim of Halema‘uma‘u crater
This photo shows an HVO scientist working in the hazardous closed area of Hawai‘i Volcanoes National Park. The scientist is using an instrument to measure the composition of the gases being emitted during Kīlauea Volcano's ongoing summit eruption in order to better evaluate the hazards and understand the eruptive activity. The scientist is equipped with safety gear, is wearing a gas mask (respirator), helmet, eye protection and other PPE, and is in constant communication with USGS and NPS staff. (Public domain.)

The mission of the USGS Hawaiian Volcano Observatory (HVO) is to monitor the active volcanoes in Hawaii, assesses their hazards, issues warnings, and advance scientific understanding to reduce impacts of volcanic eruptions. HVO personnel conduct mission-critical research in the hazardous and closed area of Kīlauea's summit to fulfill this mission, with permission and in partnership with the National Park Service. During the recent eruption, HVO staff are collecting data related to earthquakes, volcanic gas emissions, ground deformation, and fissure/lava lake behavior, in order to understand how the eruption is evolving and to assess hazards at Kīlauea's summit. This information is shared with the National Park Service and emergency managers, who make public safety decisions based on current conditions and hazards.  

Is it safe to breathe volcanic gas or vog?

Be aware that significant sulfur dioxide (SO2) emissions continue and poor air quality is likely in areas downwind of the vents as volcanic emissions react in the atmosphere to form Vog (volcanic air pollution). Vog can create an airborne health hazard to residents and visitors.  

It is very important to take measures to protect yourself if you feel your health is being affected by vog. "Sensitive groups" most likely to experience health impacts include: 

  • people with asthma, lung or heart problems 
  • older adults 
  • infants and children 
  • pregnant women 

For more information, see the following resources:

Color photograph of eruption plume
Aerial imagery collected during a USGS Hawaiian Volcano Observatory overflight at approximately 11:35 a.m. HST. The plume from the ongoing eruption rises above the Kīlauea Volcano's summit, within Hawai‘i Volcanoes National Park. Ha‘akulamanu (Sulphur Banks) is visible in the foreground. USGS photo. (Public domain.)