Hualalai volcano last erupted between 1800-1801, when it produced lava flows from 5 fissure vents that reached the sea and buried Hawaiian villages.
Hualalaibegan to erupt about 800,000 years ago and broke the surface of the sea about 300,000 years ago. The volcano has 3 rift zones, the most prominent being the northwest rift, which is about 40 km long and continues in the sea to a depth of 3000 m. Hualalai erupts much less frequently than its neighbors, with centuries rather than years or decades separating eruptions.
The most recent documented activity was a seismic swarm in 1929, which probably corresponded to a magma intrusion into the volcano. Its most recent eruption occurred in 1800-01, and lava flows erupted from 1800-01 underlie almost the entire Ellison Onizuka Kona International Airport in Keahole. Future Hualalai eruptions may pose a direct threat to Kailua-Kona and surrounding communities. Compared to Kilauea and Mauna Loa, Hualalai poses a different challenge in monitoring changes in activity.
Lava flows represent by far the greatest danger in a possible future Hualalai eruption, because although explosive pyroclastic eruptions have occurred during the Holocene epoch (the last 10,000 years), they are relatively rare and cover only limited parts of the volcano. The source of this eruption was the Wahapele Crater, a vent on the southern flank of Hualalai at 1,540 meters (5,053 feet) high. However, in 1929 an intense earthquake swarm hit Hualalai for a period of one month, which has been interpreted as due to an intrusion of magma near the surface, without a superficial eruption. For residents of the Kona area, keep in mind that Hualalai hasn't erupted since 1801; Mauna Loa is considered active but hasn't erupted since 1984.Hualalai, the third of Hawaii's active shield volcanoes, is located northwest and humid of its giant neighbors Mauna Loa and Mauna Kea.
Although 200 years have passed since the last Hualalai eruption, it is almost certain that it will erupt again. Hualalai, Mount Hualalai, Hualalai Mountain or Hualalai Volcano: it's just one name, Hualalai. Alkaline eruptions in Hualalai have generally been much less explosive than those at neighboring Kohala and Mauna Kea volcanoes. Another geologically recent Hualalai eruption was the Wahapele eruption, which probably occurred sometime between 1200 and 1400 AD.
For additional information on Hualalai volcano, visit the USGS Hawaiian Volcano Observatory (Hualalai) page.