A few weeks ago, a Volcano Watch article recounted the advance of Mauna Loa lava on the town of Hilo in 1855. Titus Coan, a fervent investigator and observer of all things volcanic, was in his mid-50s at the time
A few weeks ago, a Volcano Watch article recounted the advance of Mauna Loa lava on the town of Hilo in 1855. Titus Coan, a fervent investigator and observer of all things volcanic, was in his mid-50s at the time and walked up to the source of the flow at least seven times between August 1855, when the eruption began, and February 1856, when the lava flow stopped. By the end of the eruption, Coan understood how lava flows advanced with a level of detail that no one else had achieved before.
Hilo was again threatened by lava during an eruption sequence that started at the summit in early May 1880. After a several-month hiatus, the sequence resumed Nov. 5, 1880, from vents lower on the northeast rift zone and adjacent to the 1855 vent. Over the next few days, aa flows advanced northeastward into the saddle area and southward toward the Kapapala area on the flank of Mauna Loa.
One month later, only one flow remained active and continued to advance toward Hilo into 1881.
In his autobiography, Titus Coan said that by summer, “We could hear the explosions in Hilo; it was like the noise of battle. Day and night the ancient forest was ablaze, and the scene was vivid beyond description. By the 25th of March the lava was within seven miles of Hilo, and steadily advancing. Until this time we had hoped that Hilo would not be threatened. But the stream pursued its way. By the 1st of June it was within five miles of us, and its advance, though slow, was persistent.”
As the 1880-1881 flow moved closer to Hilo, people visited the flow more frequently. A few brave souls also ascended the flow to its source and beyond to the volcano’s summit. But at age 81, Coan was not fit for the challenge. “Were I twenty years younger, I should have been on the mountaintop also, but my time to climb such rugged heights is past,” he wrote. But he was with these younger adventurers in spirit.
Many of the people who made the long, grueling hikes also made good observations of the eruption, and they confirmed Coan’s ideas about lava flow development. The 1881 newspaper accounts by D.H. Hitchcock and others often described lava tunnels, viaducts or conduits and how those internal tubes carried lava to the advancing flow front.
The advancing lava flow split into three forks at the 2,400-foot elevation, 8.5 miles from Hilo Bay, only to reunite into a single flow at the 1,600-foot elevation, 6.3 miles from the bay. The flow again split into two forks — north and south — at the 300-foot elevation, 1.6 miles from the bay.
The north branch of the flow continued down the Alenaio stream bed and stopped about 225 feet mauka of Komohana Street. The south branch advanced a bit farther, crossing Komohana Street and going down what was then known as Kalanakamaa Gulch just south of Mohouli Street, then stalled near the intersection of Mohouli and Popolo streets, 1.1 miles from Hilo Bay. All activity at the flow front had stopped by Aug. 10, 1881.
Because the 1880-1881 lava flow reached lower elevations than the 1855-1856 lava flow, and, therefore, moved closer to Hilo and deep within the watershed of the Wailuku River, the propensity for lava flows to enter and advance through stream and river channels became obvious. Several writers used this tendency to predict the exact paths that lava flowing toward Hilo would take.
This is also the idea behind our current use of steepest descent lines, calculated from digital elevation models, to forecast future paths of lava flows because, like water, lava tends to flow downhill. With the advent of fast, cheap computers and good digital terrain models, calculations can be made quickly ahead of an actual lava flow, even in areas where stream flow has not carved out an obvious path. This tool, an offshoot of early observations, is just one of many we use to keep the public informed of potential volcanic activity and hazards.
Kilauea activity update
A lava lake within Halemaumau produced nighttime glow visible via HVO’s webcam during the past week. The lava lake level varied between 100 and 130 feet below the rim of the overlook crater.
On Kilauea’s east rift zone, the Kahaualea 2 flow remains active. The flow front stalled at 5.5 miles northeast of its vent on Puu Oo in mid-May. On Tuesday, the most distant active flows were approximately 4.4 miles northeast of Puu Oo. In addition, several small, brief lava flows erupted from spatter cones within the Puu Oo crater.
One earthquake was reported felt in the past week across Hawaii Island. At 10:25 p.m. June 20, a magnitude 3.1 earthquake occurred 3 miles south-southwest of Volcano at a depth of 2 miles.
Visit hvo.wr.usgs.gov for Volcano Awareness Month details and Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos and recent earthquakes; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.
