Volcano Watch — Age-old questions pondered prior to Kīlauea Volcano's 1927 summit eruption

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These questions were among the most frequently asked by Kīlauea visitors, according to Ronald M. Wilson in his Hawaiian Volcano Observatory weekly report on June 30, 1927. At the time, Wilson was temporarily in charge of HVO while the director, Thomas A. Jaggar, investigated volcanoes in Alaska.

Kīlauea had not erupted since July 1924, so the questions were reasonable, and one of them was easily answered. "The volcano of Kīlauea is not dead," Wilson wrote, noting that the three-year quiet phase was "but part of the cycle of the volcano."

"The second question," he acknowledged, "is not so easily disposed of…." But, a week later, it was definitively answered when Kīlauea suddenly came to life with little warning. (In hindsight, there were a few precursory signals.)

Shortly before 1:00 a.m. on July 7, 1927, a Volcano House night watchman making his rounds noticed a faint glow at Halema‘uma‘u Crater. As the glow grew brighter, he awakened hotel guests. The glow was also observed at Kīlauea Military Camp and by occupants of the Kīlauea Summer Camp cottages. Within minutes, a procession of automobiles was on the road, rushing toward Halema‘uma‘u.

By 1:40 a.m., a crowd of about 50 people, including Wilson, had reached the crater rim. They watched in awe as four lava fountains up to 38 m (125 ft) high erupted within Halema‘uma‘u, forming a lava lake that soon covered the crater floor.

Two fountains were on a talus slope on the southwest side of the crater, well above the lava lake. These vents sent rivers of lava 3–6 m (10–20 ft) wide streaming into the lake, estimated to be 9 m (30 ft) deep within the first hour. A third vent at the foot of the talus slope produced a small twin fountain at the edge of the lake.

The fourth fountain erupted from a vent below lake level on the northeast side of the crater. As lava gushed up through the lake, it set in motion waves that crossed the lake's surface to the opposite side of the crater, providing evidence of the depth and fluidity of the impounded lava.

The lava fountains produced a "thundering roar" so loud that people on the crater rim had to raise their voices to be heard. For the most part, the growing crowd watched the eruption in relative comfort, grateful for the intense heat of lava in the cold, early morning air. But occasionally, whirlwinds carried choking sulfur fumes to the crater's edge, causing spectators to hastily retreat.

The news quickly spread to Hilo. The road to Kīlauea was under construction, but bumps and potholes did not deter people intent on reaching the volcano. As soon as word reached Honolulu, hundreds of residents and visitors hurriedly booked passage on steamships setting sail to Hilo.

Within 24 hours, three of the vents ceased action. One southwest fountain remained active, feeding a voluminous stream of lava into the lake and building a 12-m- (40-ft-) high spatter cone on the talus slope.

Daybreak on July 8 revealed that the lava lake had partly drained during the night, causing the cooled crust to collapse about 3 m (10 ft) and leaving a high lava mark around its edges. Lava from the southwest cone flowed onto the collapsed crust, where it began to spread.

By July 9, the activity was less spectacular, but lava kept erupting from the cone. Lava flows on the crater floor grew in both depth and area and, by July 13, covered most of the collapsed lake surface. Over the next week, the eruption grew weaker, but sluggish flows continued, eventually raising the crater floor by about 24 m (80 ft).

On the morning of July 20, only a small amount of fume issued from the spatter cone, and, by that afternoon, all activity had ceased. The eruption was over.

The questions addressed by Wilson in 1927 could be asked today of Mauna Loa and Hualālai, quiet since 1984 and 1801, respectively, but not dead. Interestingly, Kīlauea's eruption, ongoing since 1983, has resulted in an even more difficult question to answer: "When will it end?"

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Volcano Activity Update

The lava lake deep within the Halema‘uma‘u Overlook vent remained at a relatively steady level throughout the past week. At Pu‘u ‘Ō‘ō, the lava lake hosted numerous overflows onto the crater floor last weekend. By the beginning of the week, and continuing at least through Thursday, July 7, the crater floor surrounding the lava lake began to rise. This rise was likely caused by the shallow injection of dense, degassed magma from the lake into the layered flows that make up the crater floor. As a result, the rim of the lake was lifted vertically several meters (yards), forming a ragged palisade around the lake's perimeter. Two new vents opened on the south side of the crater during the past week, as well. Both produced small, sluggish flows, located outside the portion of the crater formed by the collapse in March 2011.

Two earthquakes beneath Hawai‘i Island were reported felt this past week. A magnitude-2.4 micro-earthquake at 3:11 a.m., HST, on Saturday, July 2, 2011, was located 3 km (2 mi) north-northeast of Hōnaunau at a depth of 12 km (7 mi). A magnitude-3.0 earthquake at 6:41 a.m. on Friday, July 1, was located 22 km (14 mi) northwest of Kailua at a depth of 36 km (23 mi).