Hualālai is the third youngest and third-most historically active volcano on the Island of Hawai‘i. It is considered to be in the post-shield stage of activity. Six different vents erupted lava between the late 1700s and 1801, two of which generated lava flows that poured into the sea on the west coast of the island. The Keahole Airport, located only 11 km (7 mi) north of Kailua-Kona, is built atop the larger flow. The oldest dated rocks are from about 128,000 years ago and it probably reached an elevation above sea level before 300,000 years ago. The volume of Hualālai is 12,400 km3 (2,975 mi3). Its area is 751 km2 (290 mi2).
Though Hualālai is not nearly as active as Mauna Loa or Kīlauea, geologic mapping of the volcano shows that 80 percent of Hualālai's surface has been covered by lava flows in the past 5,000 years. In the past few decades, when most of the resorts, homes, and commercial buildings were built on the flanks of Hualālai, earthquake activity beneath the volcano has been low. In 1929, however, an intense swarm of more than 6,200 earthquakes rattled the area around Hualālai Volcano for more than a month. The earthquakes were most likely caused by an intrusion of magma beneath the volcano. Two large earthquakes (each about magnitude 6.5) destroyed houses, water tanks, stone fences, and roadways. For these reasons, Hualālai is considered a potentially dangerous volcano that is likely to erupt again.