Earthquake News

Seismic monitors on Mount Hood pick up airwaves from Tongan volcanic eruption


Source: Oregon Live


Tongan eruption

Early Jan. 15, 2022, sensitive monitoring equipment on the flanks of Mount Hood picked up airwaves from the Tongan volcanic eruption.

Seismic monitors on Mount Hood picked up the aftermath of the underwater volcanic eruption near Tonga in the Pacific Ocean, the U.S. Geological Survey said Saturday.

The USGS on Twitter credited the sophisticated equipment deployed in the Cascades for seismic monitoring for picking up the airwaves from the eruption. The peak -- when the airwave arrived at Mount Hood -- was at 13:21:07 UTC (5:21 a.m. Pacific Time), and that was recorded at Lamberson Butte, near Parkdale. Mount Hood is one of the most seismically active volcanoes in the Cascade Range.

Satellite images showed a huge eruption, with a plume of ash, steam and gas rising like a mushroom above the blue Pacific waters north of New Zealand. A sonic boom could be heard as far away as Alaska.

Tsunami advisories were issued for Hawaii, Alaska and the U.S. Pacific coast. The U.S. Geological Survey estimated the eruption caused the equivalent of magnitude 5.8 earthquake. Scientists said tsunamis generated by volcanoes rather than earthquakes are relatively rare.

The first waves to hit the continental United States measured about 33 centimeters (1 foot) in Nikolski, Alaska, and 59 centimeters (1.9 feet) in Adak, Alaska. A wave of about 79 centimeters (2.6 feet) was observed in Monterey, California, according to the U.S. National Tsunami Warning Center.

There is not a significant difference between volcanoes underwater and on land, and underwater volcanoes become bigger as they erupt, at some point usually breaching the surface, said Hans Schwaiger, a research geophysicist with the Alaska Volcano Observatory.

With underwater volcanoes, however, the water can add to the explosivity of the eruption as it hits the lava, Schwaiger added.

Before an explosion, there is generally an increase in small local earthquakes at the volcano, but depending on how far it is from land, that may not be felt by residents along the shoreline, Schwaiger said.

Earlier, the Matangi Tonga news site reported that scientists observed massive explosions, thunder and lightning near the volcano after it started erupting early Friday. Satellite images showed a 5-kilometer (3-mile) -wide plume rising into the air to about 20 kilometers (12 miles).

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