The eruption of Mauna Loa in the spring of 1868 and the deadly phenomena surrounding it were one of the greatest natural disasters in Hawaiian history. 77 Hawaiians died in the associated tsunami and landslides.
As with most eruptions of Mauna Loa, the 1868 eruption began at its summit caldera, Moku‘āweoweo. On March 27th, as if the volcano were sending out a warning for all to see, a column of smoke was seen emanating from the top of the mountain. Some on the island reported seeing a glow from molten lava.
Earthquakes and tremors soon began to increase. The following day, March 28th, a 7.0-magnitude earthquake occured in Kaʻū, on the southern portion of the island, causing extensive damage. A steady stream of quakes followed in the subsequent days at rates of 50- 300 per day, with at least one as large as a 6.0-magnitude.
At approximately 4:00pm on April 2nd, the great Kaʻū earthquake struck. It is thought to have been 7.9-magnitude, the same intensity as the massive quake that would later decimate San Francisco in 1906.
"Such a convulsion has no parallel in the memory, the history, or the traditions of the Hawaiian Islands."
- The Reverend Titus Coan
Damage was immediate and it was extensive. At Waiʻōhinu, a large stone church reportedly collapsed just seconds after the shaking began. Landslides occurred as far north as Waipio. The quake unleashed river of mud about a half-mile wide and twenty feet deep in Wood Valley, burying ten homes and killing thirty one people as well hundreds of livestock at William Reed's Kapāpala Ranch. "...the falling of walls and chimneys, the swaying of trees, the trembling of shrubs, the fright of men and animals, made throughout the southern half of Hawaii such scenes of terror as had never been witnessed before," the Reverend Titus Coan wrote.
The USGS Hawaiian Volcano Observatory estimates that the entire island south and east of Mauna Loa's summit and rift zones moved seaward and subsided several meters during the earthquake. The tremors were so intense that they also spurred a small eruption in Kīlauea Iki crater and reportedly caused cracks at the summit of Kīlauea.
Further destruction soon came from the sea. A massive tsunami hit large swaths of the coastline with at least eight waves over a period of several hours. One wave was estimated to be more than 20 feet (6 m) high in Ka‘ū. Villages at ʻĀpua Point and Keauhou, now within Hawaiʻi Volcanoes National Park, were decimated. Some settlements were never rebuilt.
On the evening of April 7th, five days after the 7.9-magnitude earthquake, lava burst forth from a fissure on the Kahuku Ranch, about ten miles inland from the coast. Fountains of lava by some accounts were 500 to 1,000 feet (150 to 300m) high near the residence of Captain Robert Brown. The main lava flow was about a mile wide, with three smaller branches and managed to reach the ocean within four hours.
"And from the whole length of this orifice the lava rushed up with intense vehemence, spouting jets one hundered to two hundred feet high burning the forest and spreading out a mile wide"
-The Reverend Titus Coan
The flow lasted five days and destroyed 4,000 acres of grazing land on the Kahuku Ranch. One family was reportedly trapped for ten days after the violent flows created a kīpuka around their home.
Upon receiving news of the damage and destruction on April 9th, King Kamehameha V departed Oʻahu for Hawaiʻi Island to provide relief to the victims. The party landed in Hilo on April 15th and toured the damage along the Puna and Kaʻū coastlines. Queen Emma appealed to citizens of the islands to donate to the relief.
In total 77 Hawaiians lost their lives due to the tsunami and landslides spurred by the eruption. However, the fatalities could have been much worse, were the island as populated as it is today. The eruption of 1868 still stands as one of the deadliest disasters in the modern history of Hawaiʻi.