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Climate and Environment

Attention Southern California: Here's Why A Tsunami Advisory Was Issued Saturday

A sign on a pole has an arrow pointed upward and reads: Tsunami evacuation route.
Tsunami evacuation routes in Seal Beach.
(Megan Garvey
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A tsunami advisory was issued Saturday morning due to a massive undersea volcano explosion in the South Pacific that sent waves rolling east toward the U.S. West Coast.

The U.S. National Tsunami Warning Center says we should be prepared for higher water in bays and harbors. Waves due to the tsunami were expected to peak in Southern California between 7:30-8 a.m. Saturday morning. But the effects of the tsunami are longer lasting. Meteorologists and seismologists warned that the waters near shore are likely hazardous.

As Lucy Jones, a noted seismologist, said to her followers on Twitter: "Moving water has huge momentum."

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Orange County alerted people by cell phone in the morning and again after noon that all beaches — from Seal Beach to San Clemente — there have been closed. The Orange County sheriff took that step as a precaution. City police departments in the O.C. closed their piers.

Beaches in San Diego County were also closed.

Beach web cams and eyewitnesses indicated that the waves hitting beaches here did not seem extraordinary.

Further up the coast, Port San Luis reported flooding that reached parking lot. The south facing beach is just north of Pismo. The National Weather Service said tide gauges there indicated some of the highest tsunami waves recorded on the West Coast.

The Origin

The surge was generated by a huge explosion of an undersea volcano near the South Pacific island nation of Tonga on Friday.

The coast of the main island in Tonga was swamped by a surge of water and falling ash. The initial explosion was captured by a satellite camera.

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Why You Should Be Careful

The National Weather Service is urging caution, since rip tides are likely even if massive waves are not.

"A tsunami capable of producing strong currents hazardous to swimmers, boats, and coastal structures is expected," the NWS office is L.A. tweeted this morning.

Seismologist Lucy Jones had these reminders:

Here's a guide to warning levels:

What questions do you have about Southern California?