An eruption of the Shishaldin Volcano in Alaska has "gradually declined," according to the Alaska Volcano Observatory.

However, low-level ash emissions below 10,000 feet above sea level continue and a significant ash plume was produced Tuesday morning, reaching a height of around 30,000 feet. 

The plume has since detached, but remained visible between 60-280 miles away from the volcano. 

The National Weather Service issued a SIGMET for the cloud. SIGMETs are brief descriptions of the development and occurrence or expected occurrence in time and space of specified en-route weather phenomena which may affect the safety of all aircraft operations, according to the agency. 

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The aviation alert and Volcano Alert Levels have been reduced. 

The volcano, located in the Aleutian Islands, is situated about 700 miles southwest of Anchorage, and it sits near the middle of Unimak Island. 

Unimak Island has about 65 residents northeast of the volcano in the community of False Pass. 

Shishaldin Volcano began erupting on July 11, with strongly elevated surface temperatures reported at the summit.

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A U.S. Coast Guard helicopter flew by eruptive activity the next day.

Notably, an explosion on Friday produced an ash cloud that reached up to 7.5 miles and moved southward over the Pacific, with a second smaller explosion later that day. 

The volcano, one of the most active in the Aleutian arc, is a symmetric cone with a base diameter of 10 miles.

The 660-foot-tall funnel-shaped crater often emits steam and occasional ash.

There have been at least 26 confirmed eruptions at Shishaldin Volcano since 1824. 

While most are small, the observatory said a 1999 eruption produced an ash cloud that reached 8.5 miles.

The Associated Press contributed to this report.