Haulalai is a shield volcano located on the Big Island of Hawaii (19.69 N, 155.87 W). The summit of Hualalai rises to 2523m (8271ft) above sea level. The volcano is the westernmost of the 5 major Big Island volcanoes. It has a well-developed Northwest rift zone, a moderately well-developed South-Southeast rift zone, and a poorly developed North rift zone. The most recent eruption of 1800-1801 occurred along the Northwest rift zone.

Eruptive History     Haulalai has completed its main Tholeiitic Shield Stage, during which normal and picritic tholeiitic basalts were erupted. These lavas are no longer exposed on the subaerial surface but have been dredged from submarine portions of the northwest rift zone. Presently, the volcano is mantled by alkalic lavas erupted during the post-shield stage of volcanism (mostly alkali olivine basalts but rare occurrences of Trachyte are also present). The last historical eruption at Hualalai ended in 1801. It is considered to be the third most active volcano in Hawaii, after Mauna Loa and Kilauea

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This eruption produced very fluid, high velocity lava flows that entered the ocean off western Hawaii. Overall, 5 vents issued alkalic basalt lavas, with 2 of these vents producing flows that reached the sea. The total volume of erupted lava has been estimated as >300 million m³. This eruption brought abundant xenoliths (xeno = foreign; lith = rock) up from the mantle source that originally produced the lava (see below). The highest elevation vent produced an enormous aa flow (the Kaupulehu flow) that entered the ocean as 2 discrete lobes. One of these lobes destroyed a Hawaiian village in its path. This eruption at Hualalai is believed to be concurrent with an eruption at neighboring Mauna Loa volcano. Additionally, Hualalai has been essentially simultaneously active with both Mauna Loa and Kilauea in the not so distant past (note: although, we do not in fact know if any eruptions occured simulataneously, we do know that these three volcanoes have been active during much of the last 100 to 200 thousand years).     In the image to the left, the two main lobes of the 1800-1801 eruption are displayed (Kaupulehu in orange, Huehue in red). Also shown (in brown) are the 100000 year old trachytes of Puu Waawaa), the 1859 lava flow from nearby Mauna Loa (in grey), and the Kahaluu water shaft (marked by an X""), where Hualalai generated tholeiitic basalts are found only 75 feet below the surface. The surface of Hualalai is entirely composed of post-shield alkalic basalts.

     Hualalai is well-known in Hawaii as a good source for mantle xenoliths. The A.D. 1800 Kaupulehu flow on Hualalai volcano contains abundant coarse-grained xenoliths of exceptional size and quantity, and many prehistoric vent deposits and flows of this volcano also contain abundant xenoliths. A xenolith from the 1800-1801 flow is shown below.

    Although it has been 200 hundred years since the last eruption of Hualalai, it will almost certainly erupt again. Lava flows by far pose the greatest danger in a potential future eruption of Hualalai, because although explosive pyroclastic eruptions have occurred during Holocene times (the past 10,000 years), they are relatively rare and they cover only limited parts of the volcano. The alkalic eruptions at Hualalai have been generally much less explosive than those at neighboring Kohala and Mauna Kea volcanoes. There has been no recently-detected magma-related seismicity or ground deformation at Hualalai, making it difficult to say if and when the next eruption might occur.
     Hualalai still presents a volcanic hazard as it is near populated areas. For instance, its summit is only 15km away from the town of Kailua-Kona and a flow as voluminous as the 1800 eruption could cover that distance in a few hours.
     The eruptive recurrence interval of Hualalai for all of Holocene time is on the order of 50 years (about 200 eruptions in 10,000 years). However, mapping and ¹⁴C dating studies have indicated that eruptions have occurred in clusters (groups of several eruptions over a few hundred years), separated by several centuries of inactivity.
     The Hawaiian Volcano Observatory (HVO) has maintained a seismic station located 3 km east of Hualalai's summit since 1971, which is used to monitor the volcano for signs of activity. During this period, no microearthquake swarms or harmonic tremors (both indicative of magma migration) have been recorded, although each year Hualalai experiences several magnitude 4 earthquakes. These earthquakes are usually from a deep source off the coast of the Northwest rift zone (HVO unpublished data). This seismicity is apparently not related to movement of magma. However, in 1929 an intense swarm of earthquakes struck Hualalai for a period of a month, which has been interpreted as being due to a magma intrusion to near the surface, without a surface eruption.

Last page update on 4 Jan 2004