Lava from the Mauna Loa eruption will take at least a week to reach Saddle Road (also known as Daniel K. Inouye Highway) if it continues to move at its current rate.

On Wednesday, Ken Hon, the scientist-in-charge at the Hawaii Volcano Observatory, said at the rate the lava was moving, it might take only two days for the flow to make its way to Saddle Road. By Thursday morning, Hon said at a news conference that the lava had slowed considerably. 

“There’s a lot of uncertainty here,” Hon said. “We don’t know when the lava flow or if the lava flow will reach the highway.”

Saddle Road is an important thoroughfare through the island. If the road is cut off, it will take much longer to drive from Hilo to Kona along coastal routes.

The eruption of Mauna Loa started late Sunday night, and it continues to spew lava from the Northeast Rift Zone.

A rift zone is an area below the summit where a volcano splits apart and magma easily makes its way to the surface. Once at the surface, lava flows downhill and follows the topography of the surrounding environment.  

Currently, the Northeast Rift Zone has two active fissures — fissure 3 and fissure 4 — feeding lava flows downslope. A fissure is a linear volcanic vent through which lava erupts. At least four fissures have been active since the start of the eruption.

Fissure 3 continues to be the dominant fissure. The lava from this fissure is heading toward Saddle Road. As of Thursday morning, the lava flow slowed to a rate of 0.03 miles per hour. Reports from Tuesday said that the lava was advancing at a rate of 0.08 miles per hour.

The flow front remains about 3.6 miles from Saddle Road. The flow front reached a relatively flat area known as “the saddle,” where it slowed down and spread out. 

Hon said that the lava front is “right on the divide” and it’s not clear if it will go toward the east or west side of Hawaii Island. 

A lobe of lava from fissure 4 is coming down to the east of the main lobe, which is being fed by fissure 3. 

Pele’s hair (thin glass fibers formed by volcanic gas) has been reported as far as 15 miles away from the lava flow, according to Hon. 

Winds have shifted and are now coming more from the north. Now, Hon said they expect some of the sulfur dioxide and potentially Pele’s hair to affect communities on the south end of the island, such as Naalehu and Ocean View. 

In order to relieve the traffic on Saddle Road caused by people pulling over to view the lava flow, Hawaii County will open a 4.5-mile stretch along old Saddle Road, which has an entrance directly across from Gilbert Kahele Recreation Area, according to Hawaii County Civil Defense Administrator Talmadge Magno, who spoke at the news conference. 

On the newly opened road, traffic will go only in one-direction, with the exit near Puu Huluhulu. Cars will be allowed to park along Old Saddle Road. However, the road goes through the Pohakuloa Training Area and people may not wander off the road. 

On Tuesday night, a car was struck on the shoulder lane of Saddle Road as it attempted to pull back on the main roadway after pulling over to watch the lava. Six patients were involved in the incident, with two needing medical transport for minor injuries, according to a Hawaii County news release. 

Hawaii County Mayor Mitch Roth issued an emergency rule on Wednesday that prohibits parking and walking on Saddle Road and its shoulders between mile marker 16 and the intersection of the highway and Hawaii Belt Road (also known as Highway 190). 

Jessica Ferracane, the spokesperson for Hawaii Volcanoes National Park, said during the news conference that the park continues to be opened. However, Mauna Loa Road, which is located inside the park, is closed. 

Lava from both Kilauea and Mauna Loa can be seen from the park. 

Drones are prohibited in the park, unless a permit has been granted by the Park Services, according to Ferracane. She said drones can be a hazard to wildlife, such as Hawaiian petrel and nene.

Michelle Broder Van Dyke covers the Hawaiian Islands for Spectrum News Hawaii. Email her ideas and feedback at michelle.brodervandyke@charter.com.