At 0532 on 29 November, 44 minutes after a severe earthquake beneath Hawaii's SE coast (table 1), lava erupted from a N85°E-trending fissure on the floor of Kīlauea caldera. Lava fountains were 50 m high for the first 15 minutes but decreased to 5-10 m heights for the next 75 minutes before stopping. Eruptive activity resumed at about 0830 in Halemaumau pit crater and continued intermittently before ceasing around 2200, after 16 hours of activity. Lava drained into the SW rift zone for days after the end of visible activity. Maximum horizontal displacement on the order of 3.5 m was involved in the seaward movement of Kīlauea's S flank.

Table 1. Seismic parameters of the Kalapana earthquake that occurred at 0448 on 29 November 1975. The epicenter was 30 km ESE of Kīlauea Caldera. Additional data on the important earthquake may be found in Crosson and Endo (1981).

The earthquake was the strongest in Hawaii since at least 1868, and extensive damage was reported. On the SE shore, at Punaluu, a 6-m tsunami was observed. At Halape, two people died when a wave in excess of 7 m high [swept inland] and reached 16 m up a fault scarp perpendicular to the coast. The coastal area at Halape, the area of maximum subsidence, was permanently lowered 3 m. The tide gauge at Hilo recorded a 2.5 m wave.

Further References. Crosson, R.S., Endo, E.T., 1981, Focal Mechanisms of Earthquakes Related to the 29 November 1975 Kalapana Hawaii Earthquake: The Effect of Structural Models, Bull. Seismol. Soc. Am., v. 71, p. 713-729.

Lipman, P.W., Lockwood, J.P., Okamura, R.T., et al., 1985, Ground Deformation Associated with the 1975 Magnitude 7.2 Earthquake and Resulting Changes in Activity of Kīlauea Volcano, Hawaii; USGS Professional Paper 1276, 45 pp.

Geological Summary. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Information Contacts: R. Tilling, HVO.