Kilauea Volcano continued to smoke and surge Sunday, but lava flows northeast of Puu Oo crater remained slow-moving and no threat to any communities.

The eruption, continuous since January 1983, is limited to Puu Oo and the summit caldera, where a lava lake fluctuates in height, another sign of activity in Kilauea’s subterranean magma chamber.

The lake lies within a nearly cylindrical vent cavity within the east wall and floor of Halemaumau Crater.

On Sunday the lava lake level varied between 180 and 230 feet below the Overlook Crater rim.

A small increase in earthquake activity on the southwest rift of Kilauea occurred over the past day. A magnitude-2.5 quake, the largest of the bunch, struck at 12:47 p.m. Sunday, with an epicenter 1.9 miles east-northeast of Pahala, according to the U.S. Geological Survey.

Meanwhile, on Kilauea’s east rift zone, webcams detected scattered breakouts still active between 1.4 and 4 miles northeast of Puu Oo. The flows do not present an active threat to nearby communities.

In last week’s Volcano Watch report, meanwhile, scientists at the Hawaiian Volcano Observatory said a portion of Kilauea’s south flank has slipped subtly seaward.

The movement is part of a recurring phenomenon called a “slow earthquake,” which last occurred on Memorial Day 2012, the scientists said.

Early on Oct. 14 a “tiltmeter” near Kaena Point on Hawaii island’s coastline south of Kilauea’s summit began to tilt away from the coast in a direction that is indicative of a slow earthquake. A combination of tiltmeter and GPS networks continued to detect slippage for the next two to three days.

In total the south flank slipped about 1.2 inches southeastward, the report said.

“Earthquakes typically occur along faults — places where rocks slip past each other,” the report said. “To generate the seismic waves that travel through the earth and shake our houses, roads, and buildings, the slip has to be fast, typically seconds to minutes long, depending on the size of the earthquake.

“By contrast, slow earthquakes occur over the course of several days, and in Hawaii, happen along a fault at the boundary between Kilauea Volcano and the old ocean floor. The slip associated with last week’s slow earthquake was so gradual that it did not generate seismic waves.”

However, had that slippage occurred rapidly, it would have resulted in an earthquake of about magnitude 6, the report added. The slip along the fault did, however, redistribute stresses and trigger earthquakes on adjacent segments of the fault and in the overlying crust.