Hawaiʻi Volcanoes National Park had a very different landscape before the 1970ʻs. The Maunaulu eruption changed much of the terrain around Chain of Craters Road and the upper East Rift Zone of Kīlauea. Taking place from May 24th, 1969 to July 22nd, 1974, the various phases of the eruption sent 350 million cubic meters of lava toward the sea.
Before the eruption began, there were only a few hours of sustained seismic activity. Yet, this eruption was far from surprising. In the nine months prior, three short-lived eruptions occurred in the same area on the east rift zone.
Lava fountains from Maunaulu reached heights of 1,700 feet (540m), taller than the Empire State Building (USGS Photo/J. Judd)
The first phase of the eruption lasted seven months. During this time, twelve high fountain events generated massive lava flows. These fountains reached a maximum height of 540 m (1,770 ft), taller than the Empire State Building. These fountains jetted out from fissures in the Earth that stretched for 2.5 mi (4 km). Lava flows poured into nearby ‘Alae crater until August 4th, three months after the eruption began. Cracks soon opened across the crater’s surface, causing liquid lava to drain away and empty. Lava continued to cascade into the vacant crater in the following days. These lava cascades were larger than Niagara Falls.
The Maunaulu shield itself grew first during the phase that began on December 31, 1969 and lasted until June 14, 1971. This period was characteristic of effusive flows and an absence of high fountains. As of July 5th, 1971 the shield stood 80 m (260 ft) tall and would not grow until later phases. During this time, a significant lava lake began to take form within the lava shield. Lava from this lake traveled underground and erupted from the east flank of the shield. This phase also saw the filling and disappearance of ‘Ālo‘i crater. A new fissure had opened across its floor on April 9th, 1971, causing it to fill.
From June 15 to October 15, 1971, the activity at Maunaulu waned until it stopped completely. The eruption was in hibernation. On Feburary 3, 1972 the lava returned and reentered the crater atop Maunaulu. Overflows then followed. For 15 months the lava pulsed upward and spilled over, building the shield up each time. ‘Alae crater below was growing a shield now from overflows as well, fed by a lava tube leading from Maunaulu’s lake. Lava flows during this phase reached new areas, including Makaopuhi crater. New fissures continued to break open the earth. Lava flows in and near Hi‘iaka Crater (May 5) and Pauahi Crater (November 10) soon began.
Isolated and uprift from the main eruption site, these effusions were small and brief. Finally, during the final phase, all activity returned to the Maunaulu shield. Eruptive behavior alternated between high fountains and long periods of peaceful overflows. The fountains were 40-80 m (130-260 ft) tall, and the flows caused the shield to meet its greatest height of 121 m (397 ft). After June, the lava lake became sluggish, and disappeared. The eruption ended July 22, 1974, after five years of remarkable displays. Kīlauea was finally quiet.
Left in the eruption’s path were vast fields of new rock. Cascades of lava from the eruption now drape the cliffs along Chain of Craters Road, while the inactive Maunaulu lava shield looms to the north.
Before and after the eruption of Maunaulu. (Left: U.S. Army Air Service, Hawaiian Division. Right: USGS/C. Heliker)
Depiction of the area around Maunaulu, showing the transformed landscape and re-aligned Chain of Craters Road, before and after the 1969-1974 eruption
