Crescent City and Santa Cruz were the hardest hit by a tsunami that struck the California coastline on Friday morning. The increased wave activity on San Francisco's coastline was minimal, with no major damages or injuries reported.
The tsunami warning - triggered by the devastating 8.9 earthquake in Japan - was expected to last throughout Friday, with emergency officials advising people to stay clear of low-lying areas. In response, officials in San Francisco closed the Great Highway and oceanside beaches.
"Water is coming in, going out, coming back in again, " National Weather Service forecaster Diana Henderson said.
Click on the photo to the right to see a slideshow of photos from San Francisco and the Bay Area during the tsunami warning.
In Crescent City, four people were swept out to sea. Three were injured and one was feared dead. The Crescent City harbor was completely destroyed after being pummeled by waves that rose up to 8-feet, according to the city's officials. More than 30 boats were totaled, they said.
Residents living near Ocean Beach reported that ocean activity did not appear unusual. However, there were fears in Santa Cruz that harbor boats would capsize.
The tsunami struck the region just after 8 a.m., increasing waves by a foot at Fort Point, Henderson said.
Due to the threat of large damaging waves, San Francisco police shut down the upper and lower Great Highway. The National Park Service closed Ocean Beach, Baker Beach, China Beach and Fort Funston, according to the Mayor's Office. The beaches were reopened at 4:30 p.m. Friday.
The Great Highway was closed for most of the day, reopening as well at 4:30 p.m., according to the Mayor's Office.
The tsunami threatened BART service during the peak of the Friday morning commute, but the agency opted not to halt trains. The transit agency said it feared waves exceeding 8-feet on the California coast could affect underground stations and the Transbay Tube.
“We don’t want electricity, passengers and our employees mixing with water,” BART spokesman Linton Johnson said.
Two Muni bus lines that operate on the Great Highway were rerouted — the 8-46th Avenue and 23-Monterey until the late afternoon. All other Muni service was operating normally, according to the San Francisco Municipal Transportation Agency.
In San Mateo County, hundreds of cars parked on the side of state Highway 92 early Friday morning as people evacuated coastal cities. The vehicles were being encouraged to park along nearby Canada Road.
Schools in Pacifica closed down for the day. However, class remained in session at San Francisco public schools, according to the San Francisco Unified School District.
Residents living in San Francisco had relatives calling from other parts of the country to make sure they were all right.
"I got a text message this morning at 7 a.m. from family in Ohio that said, 'Have you heard anything? Are you okay?'" said Tom Riedel, who lives in The City's Bernal Heights neighborhood. "They told me to take a video."
The City’s Emergency Operations Center has been activated, and The City’s Department of Emergency Management is in contact with the California Emergency Management Agency, the Mayor’s Office said.
The tsunami caused severe damage to the harbor in Crescent City, near the Oregon border.
Del Norte County sheriff's spokesman Bill Stevens says most boats were pulled out of the harbor in preparation for Friday's tsunami, but 35 vessels that remained are crashing into one another and sinking.
The wooden docks also are breaking apart under the force of the waves. However, the waves had not gone over the 20-foot break wall at the harbor.
Tsunamis are ocean waves produced by earthquakes or underwater landslides, according to the National Oceanic and Atmospheric Administration. The waves travel outward from the impact site in all directions, much like the ripples from a rock thrown into a pond.
Tsunami in Japanese means "harbor wave."
Wire services contributed to this report.