December 1974 Eruption

Photograph of the December 31, 1974, eruption from the Southwest Rift Zone of Kīlauea. This early morning photo shows the lava fountains feeding the eruption and throwing lava bombs to 115–130 feet (35–40 meters) high. This eruption was very brief, lasting from 2:56 a.m. to around 8:50 a.m.

USGS photo by Robin Holcomb

 

The 1974 Southwest Rift Zone Eruption

The eruption in Kīlauea's Southwest Rift Zone in 1974 is a significant event in the volcano's history. This eruption occurred twice at the summit in July and September, and once from the Southwest Rift Zone in December. Following the September summit eruption, there was a notable inflation of the summit region, indicating magma movement.

Seismic activity increased in the summit and upper East Rift Zone in the month leading up to the December eruption. By December 30, earthquakes were occurring at a rate of 2–4 per minute. At 12:10 a.m. on December 31, seismic alarms sounded, tiltmeters recorded sharp deflation, and increased tremors suggested magma movement.

The eruption began shortly after, with lava fountains observed at 2:56 a.m. in the Kaʻū Desert. Over ten fissures opened, creating a continuous lava fountain stretching over 2.5 miles long. Despite its short duration of about six hours, lava flowed approximately 7.5 miles from the source, covering a large area of the upper Southwest Rift Zone with unusually thin lava flows.

This eruption serves as a reminder of the dynamic and unpredictable nature of Kīlauea, highlighting the importance of ongoing monitoring and research to better understand volcanic activity and mitigate its potential hazards.