After a sequence of explosive eruptions documented this past weekend, the Alaska Volcano Observatory raised the aviation alert status at Cleveland to Orange, raising concerns that it could prompt air traffic cancellations for weeks.
The explosion has prompted a number of warnings from various reports, although it remains unclear whether any airlines are considering limiting flights across the Pacific.
Aleutian volcanoes are closely monitored so that air traffic can be notified if ash clouds might affect visibility. In this instance, there was originally no visual confirmation due to visibility issues; the eruptions were noted by infrasound, sound made at (typically) less than 20 hertz, a very low frequency. Inaudible to the human ear, it is typically the magma motion and explosions during the eruption that are picked up on. Infrasound travels easily through air, land and water, so it is simple for the sound to be detected even from thousands of kilometers away. Several infrasound detectors are located in Fairbanks, Alaska, where these recent explosions were picked up on.
Although infrasound technology has existed for decades, it is only in recent years that it has been incorporated widely into volcano monitoring. When visibility is poor or seismometer readings are not available, infrasound has become a key component in detecting volcanic activity.
On May 4, a second explosion was detected by infrasound and then spotted by satellite. A small plume reaching 4.5 km was spotted, and summit temperatures also elevated. Early in the weekend the activity seemed to have become more continuous, but by Sunday the seemed to have subsided. The eruption noted might have been caused by a dome collapse and then sub-plinian explosions; this is fairly common at Cleveland. Sub-plinian explosions are caused by rapidly releasing pressure on the magma underneath the summit of the volcano. When conditions clear above Cleveland, scientist may be able to determine more about the cause of this disturbance.
Cleveland’s history is well-known by scientists working closely with the volcano, but for the average spectator might not be very familiar. Reporting on the Cleveland volcano eruptions reminds both journalist and reader alike to fact-check… and to research before calling the airline in a panic.