(CNN) Earthquakes are still rattling the summit of Hawaii's Kilauea volcano, after a magnitude 5.5 quake rocked the area Sunday, according to Hawaii County Civil Defense officials.

Sunday's quake sent an ash plume 8,000 feet into the sky, but did not cause a tsunami threat, according to the Pacific Tsunami Warning Center.

There were 500 quakes in the summit area of Kilauea in a 24-hour period over the weekend -- the highest rate ever measured at the summit area, according to Brian Shiro, supervisory geophysicist at the USGS Hawaiian Volcano Observatory.

Those earthquakes have continued near the summit, according to Jim Kauahikaua, a geophysicist with the US Geological Survey's Hawaiian Volcano Observatory. He told reporters on Monday that temblors are nearly continuous at the summit and that gas emissions remain "very high."

A helicopter view from Monday morning shows lava entering the ocean at Kapoho Bay.

Lava from a fissure near the volcano entered Kapoho Bay late Sunday or early Monday, forcing billowing clouds of steam into the atmosphere as hot lava hit the cool water of the Pacific Ocean. The flow prompted warnings from Hawaii County Civil Defense authorities about laze, a nasty mashup of lava and haze that sends hydrochloric acid and volcanic glass particles into the air.