The USGS gave credit for detecting the eruption's radio waves on Twitter to the sophisticated seismic monitoring equipment set up in the Cascade Mountains. The apex, or the time the airwave reached Mount Hood, was recorded at Lamberson Butte, close to Parkdale, at 13:21:07 UTC (5:21 a.m. Pacific Time). One of the Cascade Range's most seismically active volcanoes is Mount Hood.

Satellite photographs revealed a massive eruption, with a mushroom-shaped plume of ash, steam, and gas rising above the turquoise Pacific waters to the north of New Zealand. As far away as Alaska, a sonic boom was audible.

There were tsunami warnings for Hawaii, Alaska, and the United States. Oceanic coast. According to the USGS, the eruption was the equivalent of a magnitude 5.8 earthquake. Scientists noted that tsunamis caused by volcanoes as opposed to earthquakes are rather uncommon.

About 33 centimeters (1 foot) of the first waves to strike the mainland United States were recorded in Nikolski, Alaska, and 59 centimeters (1.9 feet) in Adak, Alaska. The United States reported that a wave measuring about 79 centimeters (2.6 feet) was seen near Monterey, California. Center for National Tsunami Warning.

According to Hans Schwaiger, a research geophysicist at the Alaska Volcano Observatory, there is little difference between underwater and on-land volcanoes, and as they erupt, underwater volcanoes get bigger, typically breaching the surface at some time.

But once the water meets the lava in underwater volcanoes, Schwaiger continued, it can increase the eruption's explosiveness.

Small local tremors at the volcano typically rise before an eruption, but depending on how far away it is from land, locals by the coast may not feel them, according to Schwaiger.

Prior to that, the Matangi Tonga news site stated that after the volcano began erupting early on Friday, experts saw enormous explosions, thunder, and lightning nearby. A 5-kilometer (3-mile) wide plume was visible on satellite pictures, rising to a height of 20 kilometers (12 miles).