County declares Daniel K. Inouye Highway out of danger as eruption continues to weaken

USGS/HVO — Lava fountaining from Fissure 3 is far weaker than the last several days as effusion rates decrease.

The Mauna Loa eruption continues to lose vigor, and the Daniel K. Inouye Highway is no longer in jeopardy of being severed by lava.

Early Thursday, the U.S. Geological Survey’s Hawaiian Volcano Observatory reported that the effusion rate from Fissure 3 on Mauna Loa’s northeast flank had reduced, cutting off the supply of lava to the end of the main lava flow, and halting the advance of lava toward the highway, also known as Saddle Road.


HVO Scientist in Charge Ken Hon reiterated Friday that “there is not any threat to the highway anymore at all.”

Hon said the flow front, about 1.7 miles from the highway, will still glow and spread out over the next few days, but will not substantially move forward.

But Hon said the weakening of the volcanic activity does not necessarily indicate that the eruption is over. He said that somewhere between one-third to one-half of all eruptions in Mauna Loa’s Northeast Rift Zone undergo a transition from a highly effusive phase to a less effusive, but longer-lasting phase.

Hon said it seems clear that the highly effusive phase of the current eruption is winding down, but it is not yet clear whether a second phase will follow.

Should a second phase begin, Hon said it may be difficult for lava to leave the area around Fissure 3.

Since Thursday, lava flows from the fissure have been sluggish and unable to make it further from the fissure, which is at an elevation of about 10,000 feet. With that lava cooling and crusting over, the fissure is now becoming surrounded by fairly high masses of cooler lava that new lava may not be able to surmount.

Hawaii County Civil Defense Administrator Talmadge Magno confirmed that the county no longer considers the highway to be in danger.

“I am happy to say that the threat to Daniel K. Inouye Highway is over,” Magno said, although he added that the county will continue to monitor the situation.

Mayor Mitch Roth said Friday that starting this weekend, commercial tour vehicles with a 15-passenger capacity or less will be allowed to traverse the Traffic Hazard Mitigation Route on Old Saddle Road.

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