# Volcano Watch — An important but almost forgotten eruption of Kīlauea

Release Date:

March 5 is the 36th anniversary of one of Kīlauea's most important eruptions—the 1965 eruption that formed Makaopuhi lava lake. It was the fifth of six rift eruptions between the summit eruptions of 1961 and 1967-68, and it was the longest and largest.

Volcanic tremor began at Makaopuhi 8:02 a.m. and suddenly increased in strength at 9:21, when fountaining probably started. HVO staff members rushed down the Chain of Craters Road, which then extended to Makaopuhi. When they arrived at 9:50, a line of fountains was nearly continuous from Makaopuhi downrift past Napau Crater. The west end of the fissure was in the wall of the deep pit in the Makaopuhi double crater.

The activity stopped in Makaopuhi in the afternoon, but two other centers briefly erupted farther downrift; one built Puu Kimo 2.5 km (1.5 miles) west of Kalalua cone. A third, 1.6 km (1 mile) east of Napau, was active for 22 hours on March 9-10.

After a 15-hour pause, the eruption resumed in Makaopuhi on March 6 and lasted until March 15, forming the famous lava lake. Most visual observations were made from the scenic overlook at the crater, remains of which can be seen near today's trail to Napau, though you have to look closely amid the flood of younger lava flows from Mauna Ulu.

Adventurous trips were made to the rising lake, 210 m (700 ft) below the rim of the crater, in order to collect samples and measure how fast the lake deepened. The final lake was 84 m (275 feet) deep and 800 m (2,600 feet) wide.

The visual observations document, better than before or since, how lava circulates in a filling lava lake. Most notable are descriptions of how crust forms on a pond of lava, breaks up, and sinks. Floating surface crust became gravitationally unstable as rising gas bubbles collected beneath it. Periodically, plates of the relatively heavy crust turned on end and dove under like sinking ships. The process of crustal overturning swept across the lake like falling dominoes, renewing the crust in minutes.

Surveying on the lake surface began within 72 hours after a permanent crust had formed. Within a month, an aerial tramway was set up just east of the overlook and anchored in the middle of the crusted lake. The tramway carried supplies for drilling and scientific experiments. People climbed into the crater, using a fixed rope across the upper cliff and scrambling down loose talus for most of the way. The trip up was a lesson in dedication.

Core-drilling into the molten lava began on April 19, headed by Tom Wright and Reggie Okamura. Twenty-seven holes were drilled, the last in February 1969. Temperature measurements down each hole traced the cooling of lava and thickening of crust.

Hundreds of samples were obtained from the core, including some from molten lava itself. When the drill bit entered lava, water used to cool the bit quenched the lava to a black glass. The bit was quickly raised to keep from becoming stuck in the hardened glass. Then drilling resumed into the glass, with luck recovering an intact core that on one occasion was 1.2 m (4 feet) long. The drilling was an art form perfected by Reggie. Too little water resulted in no glass; too much resulted in geyser-like eruptions of scalding-hot glass sand from the hole.

The samples, together with numerous experiments and measurements, made the 1965 eruption of Makaopuhi scientifically famous. The results were ahead of their time and still form one of the most valuable data sets for quantitatively studying the cooling and crystallization of basaltic lava. But all good things must end; Mauna Ulu lava covered the lake a few years later, ending that marvelous natural experiment.

### Volcano Activity Update

Eruptive activity of Kīlauea Volcano continued unabated at the Puu Oo vent during the past week and provided visitors with an occasional glimpse of surface flow activity on Pulama pali and on the coastal flats. Lava is pooling in the coastal flats and not entering the ocean at this time. The closest flow is 0.8 km (0.5 mi) away from the sea coast.

No earthquakes were reported felt during the week ending on March 1.