Scientists are on alert for a possible eruption of Kilauea within Hawai‘i Volcanoes National Park following a flurry of earthquakes around the volcano’s summit.

The U.S. Geological Survey’s Hawaiian Volcano Observatory issued a warning Tuesday that an increased potential for eruption exists following a swarm of mostly small earthquakes that began late Monday afternoon and was followed by a “particularly strong sequence” of temblors at about 1:30 a.m. Tuesday that turned into a total of over 250 quakes by midday.

Most of the earthquakes were at magnitude 1 or less, and the largest was a 3.3-magnitude. But all the shaking coincided with a change in the style of ground deformation at tiltmeters in Kilauea’s summit region that could indicate an intrusion of magma 0.6 to 1.2 miles beneath the south part of the caldera, HVO said.

Ingrid Johanson, an HVO research geophysicist, said this estimated depth for a suspected dike intrusion of magma is relatively shallow and is one reason why Kilauea’s volcanic activity alert was raised to a “watch” from an “advisory” level.

“We are definitely on watch for an eruption,” she said.

HVO raised the alert level at about 5:30 a.m. Tuesday.

The “watch” level indicates a volcano is exhibiting heightened or escalating unrest with increased potential of eruption with an uncertain time frame. This level also is used when eruptions are underway while posing limited hazards. The highest alert level is a “warning,” which indicates a hazardous eruption is either underway, imminent or suspected.

All the earthquake swarms and ground deformation are concentrated within Kilauea’s southern caldera area, which is closed to the public and does not present a lava flow hazard to the public.

The last time Kilauea’s alert level was at a “watch” was during its most recent eruption, from Dec. 20 to May 26, when magma flowed from a few vents to form a lava lake within Halemaumau Crater.

HVO suggested May 27 that the summit eruption may be getting ready for a “luana iki,” or little rest, given that statistical chances have shown that most resumptions of eruptions happen within three months after a pause.

Johanson said it’s probably coincidental that all the new rumbling of Kilauea is happening right around the edge of the three-month period since the last eruption ended.

There is evidence that magma sources beneath the summit area are connected or influence each other, and Johanson said the area of activity now is similar to a magma intrusion at the summit in 2015 and could be related to sources of the most recent eruption, which ended in May.

A more distant and damaging eruption of Kilauea occurred in 2018 in the volcano’s Lower East Rift Zone. This event involved magma draining from the summit area and breaking through the surface almost 25 miles away in Puna through numerous fissures mainly in the rural Leilani Estates subdivision.

Over 107 days roughly 1 billion cubic yards of lava covered hundreds of acres of land, destroyed about 720 homes and caused damage estimated at more than $800 million.

HVO scientists are paying close 24-hour attention to Kilauea, and will issue more advisories if warranted by changing activity.

For updates and information

Including the size and location of earthquakes:

>> Visit usgs.gov/volcanoes/kilauea