Indonesia's Mount Lewotobi Laki Laki erupted on Monday, July 7, spewing an 18-km ash cloud that billowed up into the sky.
Australian officials issued a red aviation warning over the risk to flights in the region.
Indonesia's Geology Agency warned of the potential for lava flows into rivers upstream high on the volcano, and urged people to stay outside of a 7km radius of the center of the eruption.
As volcanic ash rained down on nearby villages, the agency urged people to wear masks or other mouth and nose coverings to protect against the dangers of inhalation.
Geologists recorded an avalanche of searing gas clouds mixed with rocks and lava traveling up to 5km down the volcano's slopes during the eruption.
Observations from drones showed lava filling the crater, indicating deep movement of magma that set off volcanic earthquakes.
The agency shared a video and images of the eruption on its social media channels.
Red Warning Over Danger to Flights
Australia's Volcanic Ash Advisory Center (VAAC) Darwin issued a red aviation warning about the volcanic ash plume, saying it rose to an estimated 19.2km altitude and is moving at 30 knots in a westerly direction.
"Explosive activity continues," the VAAC warning said.
Muhammad Wafid, chief of Indonesia's Geology Agency, said the size of the eruption "certainly carries a higher potential for danger, including its impact on aviation."
"We shall reevaluate to enlarge its danger zone that must be cleared of villagers and tourist activities," Wafid told The Associated Press.
Mount Lewotobi Twin Volcanoes
The 1,584-meter (5,197-foot) mountain is a twin volcano with Mount Lewotobi Perempuan in the district of Flores Timur.
Indonesia is an archipelago of 270 million people with frequent seismic activity. It has 120 active volcanoes and sits along the "Ring of Fire," a horseshoe-shaped series of seismic fault lines encircling the Pacific Basin.
Mount Lewotobi's Increase in Activity
Mount Lewotobi has shown increased activity since late 2023.
It erupted in June, unleashing a column of ash that spiraled to more than 10km in the air. The huge mushroom-shaped cloud was visible up to 90 miles away.
The eruption led to the emergency evacuation of hundreds of residents and the volcanology agency raising the alert to the highest level, warning of possible lava flows.
In November 2024, international flights to and from Bali were grounded following a powerful eruption from Mount Lewotobi.
The eruption left thousands of travelers stranded at airports in Bali, Australia, and other nearby regions while airlines struggled to manage the massive ash cloud that blanketed the skies in Flores' East Nusa Tenggara province, around 500 miles east of Indonesia's most popular tourist island.
Nine people died and dozens more were injured from the initial blast on November 4.
This article includes reporting by The Associated Press.