Hell Breaks Loose in the Pacific: Tsunami Advisory Issued for the Entire West Coast of America and Hawaii After Undersea Volcano Eruption in the Pacific Off Tonga Triggers Earthquake Measuring 7.4 Magnitude on Richter Scale. WATCH: Tonga Hit by Tsunami Waves

A tsunami advisory is in effect for the entire US Pacific seaboard and Hawaii after a massive undersea volcanic eruption triggered a 7.4 magnitude earthquake near Tonga.

‘A tsunami capable of producing strong currents that may be hazardous to swimmers, boats, and coastal structures is expected,’ the National Weather Service said in a flash bulletin on Saturday morning.

‘If you are located in this coastal area, move off the beach and out of harbors and marinas. Do not go to the coast to watch the tsunami. Be alert to instructions from your local emergency officials,’ the agency warned.

The initial tsunami wave is projected to hit Los Angeles around 7.45am PST and San Francisco at 8.10am PST.

Officials say it is not expected to cause widespread inundation, but rather coastal hazards such as rip currents and dangerous harbor currents. Authorities caution that the first waves to strike may not be the highest waves experienced in an area.

Early on Saturday, Hawaii was already seeing tsunami wave activity of up to 2.7 feet, and there were reports of waves lifting boats out of the water onto docks.

The mainland advisory now extends from California’s border with Mexico to Attu Island at the tip of Alaska’s Aleutian Islands.

In Tonga, the eruption sent large tsunami waves crashing across the shore and people rushing to higher ground.

The ‘violent’ underwater volcanic eruption in the Pacific at 5.10pm local time Friday – which was visible from space – was confirmed as the cause of the tsunami, which overwhelmed homes, buildings, fences, roads and cars in Tonga around 20 minutes later.