Eruption near Tonga leads to tsunami advisory for California coast. What about the Delta?
An underwater volcanic eruption Saturday near Tonga in the southern Pacific Ocean triggered flooding in the nation’s largest island and led to a tsunami advisory along the California coast.
The eruption at the Hunga Tonga-Hunga Ha’apai underwater volcano was visible from observation satellites orbiting earth, along with a huge plume of ash that darkened the skies of Tonga. Reports of damages in Tonga were limited as internet connection was lost at 6:40 p.m. local time, according to the Associated Press.
CNN reported that a tsunami hit the largest island in the Tongan archipelago, Tongatapu. Nearby areas including American Samoa, New Zealand and Australia issued tsunami alerts in the wake of the eruption.
U.S. officials issued tsunami advisories along Pacific coasts, affecting Hawaii, Alaska, Washington, Oregon and California.
The California Governor’s Office of Emergency Services warned that the “massive volcanic eruption” could result in “strong wave activity for 24 hours and possible damage to boats, harbors, beaches and other critical infrastructure.”
A tsunami advisory — issued by the National Tsunami Warning Center of the National Oceanic and Atmospheric Administration — is one of four levels of alerts, with the advisory being the second-highest in hazard level. It entails strong currents and dangerous waves potentially a foot high up to three feet high. The advisory indicates that people should stay out of water and away from shorelines.
Cal OES officials said that state and local law enforcement and other agencies were working to clear out beaches where strong waves were possible and to secure boats in harbors.
The National Weather Service’s San Francisco office issued a tsunami advisory to include most of the Bay Area and all of the coastline in the area, plus some inland areas as far as Napa.
Bay Area weather service officials said that waves will hit the coast in surges, similar to a high tide, and warned that the waves could pull swimmers out to sea. The forecast peak wave heights were predicted to reach 1 to 2 feet.
The U.S. Tsunami Warning System recorded initial waves around 20 cm high, or about .7 feet, in Monterey.
Delta impacts
Although NOAA’s tsunami advisory did include the west Delta, Jeff Mount, a watershed expert at the Public Policy Institute of California, said he doesn’t expect tidal action caused by the tsunami to be noticeable further inland in the Sacramento-San Joaquin Delta.
Water levels fluctuate based on tides in the West Coast’s largest estuary that begins just south of Sacramento.
“Tsunamis aren’t able to propagate that far into the Bay,” Mount said in a text message to The Sacramento Bee.
This story was originally published January 15, 2022 at 11:06 AM.