SAN DIEGO — An undersea volcano erupted near the Pacific nation of Tonga on Saturday, prompting a tsunami advisory and hazardous conditions on the water in San Diego.
Waves started arriving in Southern California shortly before 8 a.m. at a size of only 1 to 3 feet, but officials urged residents to avoid the water due to other hazards. While “widespread inundation,” meaning significant flooding, was not expected, experts said that did not mean conditions were safe on the water.
As the National Weather Service in Los Angeles explained, it’s helpful to think of tsunami advisory conditions “as surges in the currents, which after arrival can create dangerous rip currents for many hours.”
That’s why San Diego officials told people to stay off the water, move away from the beach and leave harbors and marinas.
“A tsunami capable of producing strong currents hazardous to swimmers, boats, and coastal structures is expected,” the San Diego office of the NWS said on Twitter. “Do not go to the coast to watch the tsunami. Be alert for instructions from your local emergency management officials.”
The Hunga Tonga Hunga Ha’apai volcano erupted in spectacular fashion Friday night some time after 9 p.m. PT. It sent large waves crashing across the shore in Tonga, where people rushed to higher ground. There were no immediate reports of injuries or the extent of the damage as communications with the small island remained cut off for hours after the eruption.
Video posted to social media there showed large waves crashing ashore in coastal areas, swirling around homes and buildings. New Zealand’s military said it was monitoring the situation and remained on standby, ready to assist if asked.
In Hawaii, authorities said waves slammed ashore but prompted no major emergencies. “We are relieved that there is no reported damage and only minor flooding throughout the islands,” the Pacific Tsunami Warning Center told the Associated Press, describing the situation in Hawaii.
The tsunami advisory was eventually canceled for the islands but remained in effect for California and the rest of the U.S. West Coast after noon Saturday.
Harbors and other low-lying areas in the Golden State saw some minor to moderate flooding up and down the coast, according to the NWS. A Twitter user shared video of the flooded docks and parking lot at Santa Cruz Harbor.
The scene at some of San Diego’s popular waterfronts was muted, as overcast conditions and rain showers likely further discouraged crowds. Lifeguards called surfers out of the water in Del Mar and a Harbor Police Department officer walked the pier in Shelter Island making sure people knew not to go out on boats. Rough wake rocked some of the boats that were moored there.
FOX 5 spoke with some weather-watchers who were underwhelmed by the scene at local beaches, expecting something more visibly obvious. Others were just relieved there was no immediate danger on shore after waking up to startling alerts on their phones.
Dr. Lucy Jones, one of Southern California’s foremost seismologists and go-to geological media experts, further explained why the lack of dramatic waves did not signal a lack of danger off California’s coast Saturday.
“Tsunamis are not one wave. It’s more like sloshing and that sloshing can continue for a day,” she wrote on Twitter. “Just because the first wave has passed, it is not time to go see the beach. Much tsunami damage happens in ports because of the currents. Moving water has huge momentum.”
The Associated Press contributed to this report.