But as I walk around, I notice the absence of signs about the shield volcano's eruption status or warnings of the possibility of future eruptions.
Two visitors pause nearby to take in the view. I ask them whether they know Haleakala could erupt again, and they shake their heads. One says they didn't think it could. I explain: "It probably isn't going to erupt soon, because it's been a few hundred years, but it will erupt again. It's technically an active volcano."
It was a surprise to them, and they're not alone. "Visitors often assume that Haleakala is dormant or extinct," Rebecca Roland of the National Park Service told me later in an email. "... Visitors are usually surprised to learn that Haleakala is considered an active volcano and has erupted at least 10 times in the last 1,000 years. With our most recent eruption happening only about 500 years ago."
There is no exact date of the last eruption, but the U.S. Geological Survey Hawaiian Volcano Observatory estimates the most recent ones happened outside the crater between 1480 and 1600. In one eruption, the volcano sent lava from its southwest rift zone to the sea, covering portions of the coast between Kanaio and Keoneoio, forming the bay that people commonly call La Perouse Bay .
It's not ancient history, and oral history places it even sooner. When missionary Edward Bailey lived on Maui in 1841, Native Hawaiians told him that their grandparents witnessed the last eruption. As late as the early 1900s, families were still passing down memories of the event. (Scientists think that it's possible Hawaiians witnessed the eruption, but the time frames might not be accurate.)
As a volcano whose formation began over 1 million years ago, Haleakala operates on a far different timeline than our own. A thousand years is just a fraction of a second in its history.
While it hasn't erupted in hundreds of years, that doesn't "preclude the possibility of an eruption in the lifetime of anybody who's alive today," Michael Zoeller, a geologist with the Hawaiian Volcano Observatory , told SFGATE. Zoeller said USGS has begun to move away from labels, such as "active" or "dormant," but if he had to choose one, he said Haleakala is considered active.
"It's not as active as Kilauea and Mauna Loa , but it's not a long-dormant volcano," he said. "... Maybe we're moving into a period of quiescence, but we can't rule that out entirely that it might erupt, you know, sometime in the next few centuries."
This doesn't mean the island should expect a catastrophic explosion. Hawaii's volcanic eruptions tend to produce slow-moving lava flows and lava fountains, rather than the eruptions associated with stratovolcanoes, like Mount St. Helens .
"The highly explosive eruptions that concern visitors are characteristic of composite volcanoes which have thick, viscous magma that traps gases and lead to pressure buildups," the Park Service's Roland said. "By contrast, Haleakala is a shield volcano, which erupts frequently but non-explosively, often forming lava fountains at the eruption site but not impacting any area outside of the flow itself."
She said the chance of "an eruption affecting the park is minimal," and USGS would warn them of the likelihood of an event ahead of time.
Forecasting Haleakala's eruption
Farther from Hawaii's volcanic hot spot underneath Kilauea and Mauna Loa on the island of Hawaii, Haleakala behaves differently.
"It's not like Kilauea and Mauna Loa, where there's like a magma chamber sitting a few kilometers below ground level that we can monitor with our seismic instruments and our deformation instruments," Zoeller said. "But it can erupt."
He explained that when the volcanoes move away from the hotspot, the magma comes up from a greater depth in the mantle: "And so there's not much that we can monitor that actually tells us what the volcano's activity level is, so that's one of the challenges we face with Haleakala."
Zoeller said that to the best of his knowledge, there has never been any "shallow swarm of seismicity under Haleakala that was indicative of any magma transport."
If an eruption were coming, there would be a lot of earthquakes first.
"We would, especially for an older volcano, where a lot of rock needs to get broken for the magma to get to the surface, there would be a ton of seismicity as that magma is coming to the surface. We would also probably see significant ground deformation," Zoeller said.
On top of Haleakala, a GPS instrument and seismometer monitor for these activities. An eruption would most likely occur in one of the same areas active during the past 1,500 years: the southwest rift zone, the east rift zone or summit region, Zoeller said.
The flows from the rift zones could reach Keoneoio Bay to the southwest or the area from Hana Airport to Waianapanapa State Park in East Maui. "The flows from within Haleakala Crater can go out into Keanae valley to the north or the Kaupo valley to the south," Zoeller said. "The rest of the volcano is much lower hazard."
The areas are highlighted as Zone 1 on the USGS lava flow hazard map, generally used for county planning purposes. The map lists zones across Haleakala from Zone 1 to Zone 4; the lower the number the higher the risk. While 736 people are estimated to live in Zone 1, if an eruption affected Zone 2, it would affect over 20,000 people. The greatest number of people in Zone 2, over 19,000, are living in the Kihei to Makena area, which includes Wailea. Vacation rentals and resorts line the coast, making it also highly popular with tourists.
Lava flows can destroy homes, businesses and infrastructure. In Kihei to Makena, there is an estimated $8.3 billion in building replacement cost.
Emergency preparation
Haleakala is the last active volcano on the island; the island's other volcano, Mauna Kahalawai (also known as the West Maui Mountains ), is extinct. If signs of renewed activity were detected, Zoeller said the Hawaiian Volcano Observatory would issue volcano activity notices, similar to what's being done at Kilauea, and coordinate closely with Maui County to alert residents and offer guidance.
"We would almost certainly be working with the Civil Defense Agency on Maui to get the message out to residents of the island and work with them on any mitigations for the eruptive activity, such as getting, you know, getting people evacuated or whatever else needs to be done to keep get people out of harm's way," he said.
A volcanic eruption could also lead to cascading impacts, such as destabilized slopes. "As ash and debris accumulate, they increase the weight on slopes, potentially leading to landslides," according to a 2025 Maui County Hazard Mitigation report. "Air quality in Maui County can be significantly degraded by volcanic eruptions, as large amounts of gases are released into the atmosphere, which creates vog and can substantially cause respiratory problems and exacerbate health issues, particularly for vulnerable populations."
Maui Emergency Management Agency Administrator Amos Lonokailua-Hewett told SFGATE in an email that while the probability is "very low," the agency has plans in place should a Haleakala eruption occur.
"Should volcanic activity present a threat, MEMA would work closely with the United States Geological Survey ( USGS ) and other agencies responsible for monitoring volcanic activity," Lonokailua-Hewett said. "MEMA would follow their scientific guidance in communicating timely information, protective actions and any necessary warnings."
He added that residents should prepare ahead of time by staying informed, prepping with emergency supplies, and "developing evacuation and communication plans with their ohana."
Back at the summit, there's no sign of an eruption, just as there has been none for centuries. Everything is calm. The crater sits quietly as the sun starts to set behind me, and visitors line up folding chairs in the parking lot, waiting to watch the sunset.
It's a beautiful, peaceful place. In the moment, it is easy to forget that lava once flowed here — and that it could again.
Editor's note: SFGATE recognizes the importance of diacritical marks in the Hawaiian language. We are unable to use them due to the limitations of our publishing platform.
© 2026 SFGate, San Francisco. Distributed by Tribune Content Agency, LLC.
