Volcano Watch — Description of Kīlauea eruptions started at a very opportune time

The next morning, they decided to investigate and discovered a very recent fissure eruption along the Southwest Rift Zone of Kīlauea Volcano. Later geological studies revealed that the source of this eruption was a 9.2 km-long (5.7 mi-long) fissure that fed lava to the south into the sea. There were no spatter cones built by the eruption, and the lava seemed to have moved quickly. “The inundation was sudden and violent, burnt one canoe, and carried off four more into the ocean” according to William Ellis, chronicler of this island tour.

A nearby farmer informed them that the fissures opened about “11 moons” earlier, followed by a slight earthquake “2 moons” before their visit. The eruption probably occurred sometime after the earthquake. The area was still too hot for the missionaries to stand for long, so they moved on toward the volcano, Kīlauea.

The next day, August 1, 1823, the group arrived at Kīlauea Crater. “After walking some distance … we … came to the edge of the great crater, where a spectacle, sublime and even appalling, presented itself before us.… Astonishment and awe for some moments rendered us mute, and, like statues, we stood fixed to the spot, with our eyes riveted on the abyss below.”

They were the first to publish a description of Kīlauea Crater. About 150 m (500 ft) below the crater’s rim, there was a “black ledge” of hardened crust extending all the way around the inside of the crater, with the floor a few hundred meters below. At the time of their visit, the floor of the crater “was covered with lava,” probably an active lava lake.

“It was evident that the large crater had been recently filled with liquid lava up to this black ledge, and had … emptied itself into the sea … in all probability this evacuation had caused the inundation of the Kapapala coast … about three weeks prior to our visit,” Ellis wrote. This deduction was very astute.

During repeat visits to the crater over the next two years, the missionaries observed that the level of activity decreased with each visit and that the crater was filling up.

The missionaries had stumbled on a fundamental behavior of Kīlauea volcano: the crater floor subsides and lava drains away, often fueling an eruption along one of its two rift zones, only to slowly refill before the process starts again.

The next of these subsidences occurred early in 1832. Missionary Sheldon Dibble, who resided in Hilo, experienced earthquakes and saw an increase in the glow visible from the volcano. Almost two weeks later, Dibble traveled to the crater and saw what had happened. The bit of crater rim between Kīlauea and Kīlauea Iki Crater (now called Byron’s Ledge) had been “rent by the convulsive throes which shook the whole island.” Lava poured into Kīlauea Iki Crater, and the floor of Kīlauea Crater subsided, just as it did in 1823.

The sequence replayed in the spring of 1840 when a voluminous eruption of lava, which started high on the volcano’s East Rift Zone, kept erupting from fresh fissures lower on the rift zone and ultimately entered the ocean north of Kapoho. Again, Kīlauea Crater had filled between 1832 and 1840, and the floor had subsided, coincident with the East Rift Zone eruption. The 1840 eruption was missionary Titus Coan’s introduction to Kīlauea’s sequence.

The same sequence, but on a smaller scale, occurs at the Pu‘u ‘Ō‘ō vent. Over the past several years, the crater floor subsided and refilled, only to subside again, coincident with an outpouring of lava from somewhere nearby. The sequence occurred three times in 2011 and, most recently, on June 27, 2014.

Recognizing this sequential behavior allows us some ability to forecast what volcanic activity might come next, but not when. To improve our forecasts, we continue to look for the clues to help us understand the timing of the sequence.

————————————————————————————————————————————————————————————————

Volcano Activity Update

A lava lake within Halema‘uma‘u produced nighttime glow that was visible via HVO’s Webcam during the past week. The lava lake level dropped early in the week, reaching about 50 m (~165 ft) below the rim of the Overlook crater, before rising back to about 30 m (~100 ft) by Thursday, July 17.

On Kīlauea’s East Rift Zone, the lava pond constructed over the June 27 breakout point has been abandoned, and, instead, tube-fed lava flows have begun to advance toward the northeast. These flows have reached roughly 2 km from the vent. At Pu‘u ‘Ō‘ō, the crater continues to subside, though sporadically. Pits that formed in the crater floor after June 27 contain small lava ponds.

One earthquake was reported felt during the past week on the Island of Hawai‘i. On Saturday, July 12, 2014, at 1:16 p.m., HST, a magnitude-2.9 earthquake occurred 3 km (2 mi) southwest of Laupāhoehoe at the depth of 15 km (10 mi).