Hualālai is one of the five massive shield volcanoes that form the Island of Hawaiʻi, or the Big Island. It is the westernmost of these volcanic peaks, dominating the landscape above the Kona Coast. This volcano rises to an elevation of 8,271 feet above sea level and has significantly shaped the topography and history of the western side of the island. Although it is not erupting constantly like its neighbor Kīlauea, Hualālai remains an active and closely monitored geological feature.
The Defining Event: The 1801 Eruption
Hualālai last experienced a major eruption event between 1800 and 1801, marking the most recent episode of surface activity on the volcano. This eruption was characterized by highly fluid alkalic basalt lava flows that originated from vents along the volcano’s northwest rift zone. The event produced two distinct flows that traveled downslope across the western flank and eventually poured into the Pacific Ocean.
One of these flows, known as the Kaʻūpūlehu flow, was an ʻaʻā flow that divided into two major lobes as it advanced toward the coast. This flow overran a traditional Hawaiian village and a valuable three-mile-long fishing pond, significantly altering the local ecosystem and the lives of the residents. The second notable flow, the Huehue flow, created the extensive lava plain upon which the Ellison Onizuka Kona International Airport is now situated.
This eruptive episode permanently changed the coastline, adding new land to the island as the flows solidified where they met the sea. The 1800–1801 eruption is the only historical eruption of Hualālai with reliable written records, providing a reference point for its eruptive behavior. Geological evidence suggests lava was also erupted around 1784, but the 1800–1801 activity is recognized as the most recent major event.
Hualālai’s Place in Hawaiian Volcanism
Despite the long period of quiet since the 19th century, Hualālai is classified as the third most active volcano on the Island of Hawaiʻi, following Kīlauea and Mauna Loa. The volcano is considered to be in the post-shield stage of its development, characterized by less frequent but often voluminous eruptions. Its long-term geological record indicates that approximately 80% of its surface has been covered by lava flows in the last 5,000 years.
Hualālai’s eruptive frequency is estimated to be roughly two to three times per 1,000 years, meaning its average repose interval is around 200 to 300 years. This long interval is what distinguishes it from the more frequently erupting Kīlauea and Mauna Loa. Eruptions typically occur as fissure events along its three main rift zones, which radiate to the north, northwest, and southeast from the summit.
The volcano’s eruptive history also includes a significant seismic event in 1929: a month-long swarm of more than 6,200 earthquakes. Scientists believe this intense seismic activity was caused by a shallow intrusion of magma beneath the volcano’s surface, indicating that magma is still actively moving within the volcanic system. This seismic swarm serves as a reminder of the volcano’s potential for renewed unrest.
Assessing Future Activity and Hazards
Hualālai is currently classified by the U.S. Geological Survey as a high-threat volcano, acknowledging its potential for future activity and proximity to major population centers. The entire volcano is designated as Lava Flow Hazard Zone 4 on the island’s nine-zone scale. This zone implies a lower probability of lava flow coverage compared to Kīlauea and Mauna Loa (Zones 1 and 2), but still represents a serious risk.
The Hawaiian Volcano Observatory (HVO) maintains a close watch on Hualālai by monitoring for specific signs of renewed activity. Monitoring efforts include continuous Global Positioning System (GPS) instruments and seismometers that track ground deformation and earthquake activity. These instruments are designed to detect subtle changes in the shape of the volcano or increases in seismic events that could signal magma movement and an impending eruption.
The steep slopes and short distance to the coast mean that any lava flow from a future eruption could reach the populated Kailua-Kona area in a matter of hours. This rapid travel time is a significant hazard to the communities, resorts, and infrastructure built directly on or downslope of its flanks. Although the volcano is currently quiet, its long-term pattern of activity suggests that an eruption is expected again in the coming decades.