Volcano Watch — Mauna Loa lava flow blazes a trail for the Saddle Road

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With the recent downgrade of the Volcano Alert Level for Kīlauea's June 27th lava flow that has been threatening the Pāhoa area, it's interesting to take a look back at the 1880–1881 Mauna Loa lava flow and the threat that it posed to Hilo.

Hilo was again threatened by a Mauna Loa lava flow in 1881...

A sketch by Joseph Nāwahī showing the 1881 lava flow approaching Hilo. (Courtesy of National Park Service, Hawai‘i Volcanoes National Park, HAVO 394, Volcano House Guest Register 1873 to 1885, illustration by Joseph Nāwahī, February 21, 1881.)

(Public domain.)

On the evening of November 5, 1880, people in Hilo and at the Volcano House Hotel at the summit of Kīlauea noticed a glow on Mauna Loa—produced by an eruption located northeast of the volcano’'s summit. A vent at about the 3,200 m (10,500 ft) elevation produced one lava flow that moved to the southeast and stalled about 2.5 km (1.5 mi) from Highway 11 near Kīlauea caldera. A second vent, immediately downslope of the first, erupted a pāhoehoe lava flow that advanced to the northeast toward Hilo.

By January 1881, the northeast flow was estimated to be about 30 km (18 mi) from Hilo. This flow was of interest to Hilo residents, but not a big concern. However, by April, the flow had split into three branches in the vicinity of what is now Ka‘ūMANA City, a subdivision at the upper Hilo city limits, and advanced to within 11 km (7 mi) of the town. By the beginning of July, a single branch was only 4 km (2.5 mi) from Hilo.

The flows were initially difficult to access. But by July, the flows had moved close enough to Hilo that residents and visitors alike were frequently trekking up to the flow to watch its progress. They observed that the pāhoehoe would advance very quickly as narrow fingers for short periods of time and then stall, only to repeat the process a few hours or days later. Astonishing stories of narrow lobes of lava advancing hundreds of feet in a few hours were common.

Observers would occasionally note that the lava sometimes occupied a ravine or gulch where water flowed during heavy rains. As the flows got closer to Hilo, people often noticed that warm water seemed to flow out from under the active lava.

As the eruption continued, Hilo residents became alarmed, and many started moving their belongings out of harms way. The branch closest to Hilo split into two lobes, with one headed down ‘Alenaio gulch toward the center of Hilo, and the other headed down KALANAKAM‘A‘ā gulch (near and parallel to Mohouli Street) toward the Waiākea Fishponds and Sugar Mill (Wailoa State Park). Everyone feared that the lava would cut through town and enter Hilo Bay.

Just as concern was getting intense, the leading tips of both lobes stalled on or about August 10th with the KALANAKAM‘A‘ā lobe a little more than 1.6 km (1 mi) from Hilo Bay. The ‘Alenaio lobe didn’t quite reach Komohana Street. The lava had destroyed only one house near the current location of Kaumana Elementary School. By August 19th, the lower portions of the flow were inactive.

This Mauna Loa flow differed from Kīlauea's June 27th flow in two significant ways. The Mauna Loa 1880–1881 flow is about twice the length of the June 27th flow, and the Mauna Loa eruption rate was probably higher.

But there were also some similarities. The Mauna Loa 1880–1881 and the Kīlauea June 27th lava flows were both pāhoehoe and were active for about 9 months before their threats were reduced. Both flows greatly concerned the people who lived and worked downslope of the advancing fronts, but the flows consumed only a single house before their leading edges stalled. And both flows cut a swath through heavily forested land.

But in the case of the 1880–1881 Mauna Loa flow, the open swath it cut through the forest eventually improved travel from Hilo to Waimea and Kona via the saddle between Mauna Loa and Mauna Kea. Years later, the Saddle Road, as it is now known, took advantage of this path. Today, Saddle Road crosses four Mauna Loa flows—the 1880–1881, 1855–1856, 1899, and 1935 flows—between mile markers 3 and 29.

While the 1880–1881 Mauna Loa eruption may have had a beneficial aspect—blazing a trail for Saddle Road—that's not always the case with active lava flows.


Volcano Activity Update

Kīlauea's East Rift Zone lava flow continues to feed three areas of breakouts near Pu‘u ‘Ō‘ō. The breakout 6 km (4 mi) northeast of Pu‘u ‘Ō‘ō was the farthest downslope activity observed on Tuesday, March 24. The lava flow near Pāhoa is no longer active.

There have been no major changes at Kīlauea's summit vent, which continues to host an active lava lake. The lava lake level continues to fluctuate, with the level rising over the past week. The lava level was 37 m (120 ft) below the rim of the Overlook crater on Thursday, March 26.

There were no earthquakes reported felt on the Island of Hawai‘i during the past week.