By Ray Sanchez, Amanda Watts and Dakin Andone, CNN

(CNN) -- A magnitude 7.0 earthquake that struck near Anchorage, Alaska, on Friday morning caused extensive damage to buildings and roads, sent residents scurrying for cover and triggered a tsunami warning for a time, authorities said.

The quake struck about 8:30 a.m. local time some 10 miles northeast of Anchorage, at a depth of 21 miles, according to the US Geological Survey. The tsunami warning was later canceled.

Social media and television news video depicted scenes of chaos, including students taking shelter under desks while sending texts from their phones, roads that had been buckled, items tumbling from grocery store shelves, hospital workers scrambling for cover, and panicked attorneys under desks as a courtroom rocked from side to side.

The quake also knocked CNN affiliate KTUU off the air. Items rained down from shelves at the station, news director Tracy Sabo told CNN's Sara Finch.

"It was absolutely terrifying," Kristin Dossett, a resident of Palmer, Alaska, told CNN.

She said it was the most violent quake she felt in her 37 years in a region where temblors are common. One aftershock caused her piano to move a foot and half from the wall.

"It shook like I have never felt anything shake before," Dossett said. "It just didn't stop. It kept going and got louder and louder, and things just fell everywhere — everything off my dressers, off my bookcases, my kitchen cupboard. Just broken glass everywhere."

Seismologists predict more aftershocks in coming days and weeks

Gov. Bill Walker issued a disaster declaration, according to a post on his Facebook page.

There were no reports of fatalities or injuries so far. The Kenai Peninsula Borough School District said all district students were safe.

The US Geological Survey has reported dozens of aftershocks. The largest, registering 5.7, was located in the city of Anchorage. Seismologists predicted dozens more in the coming days and weeks.

The Anchorage Office of Emergency Management for a time urged residents to shelter in place.

The Municipal Light & Power utility reported that between 7,000 and 10,000 customers were without power.

"I could tell this was bigger than anything I'd been in before, and it wasn't going to stop," resident Philip Peterson said.

Peterson was in a multistory building in downtown Anchorage as the structure swayed and coffee mugs fell from tables and tiles from the ceiling.

"I just jumped under my desk and had to ride it out," Peterson said.

Michael West, the Alaska state seismologist, told CNN the 7.0 earthquake was felt up to 400 miles outside of Anchorage. West said damage reports across the region were beginning to arrive at the Alaska Earthquake Information Center.

President Trump tweets: 'Federal Government will spare no expense'

The White House said via Twitter that President Donald Trump, who is in Argentina, had been briefed on the disaster.

Trump tweeted: "To the Great people of Alaska. You have been hit hard by a 'big one.' Please follow the directions of the highly trained professionals who are there to help you. Your Federal Government will spare no expense. God Bless you ALL!"

Former Alaska governor and vice presidential candidate Sarah Palin tweeted that her house is not intact after the quake, but did not elaborate on specific damage.

"[Pray] for Alaska. Our family is intact -- house is not... I imagine that's the case for many, many others. So thankful to be safe; praying for our state following the earthquake," she said on her verified Twitter account.

The Dena'ina Civic and Convention Center in downtown Anchorage was opened as a shelter for people unable to get home.

Two of the city's main hospitals -- Alaska Regional and Providence Alaska Medical Center -- sustained damage but emergency rooms were open, according to hospital officials.

The Anchorage Police Department said in a statement that it was handling "multiple situations" and reported "major infrastructure damage" across the city.

At Ted Stevens International Airport, the Federal Aviation Administration implemented a ground stop for flights.

Four airports were closed: Ted Stevens International Airport, Adak Airport, Merrill Field Airport and Fort Richardson Airport.

The FAA said the tower at Ted Stevens was evacuated at one point.

International Airport Road near Ted Stevens has been damaged, the airport said via Twitter, advising motorists to use extreme caution.

Alaska Airlines' operations at Ted Stevens were later lifted and flights started to arrive and depart from the airport, according to the airlines' website.

Blair Braverman said she was staying in a hotel with her husband when the quake hit. She grew up in California and was familiar with earthquakes "but this was next-level," she said.

"The bed started shaking, everything was shaking so dramatically," she told CNN.

"My husband sort of crawled across the room and threw himself on top of me and we crawled to the bathroom together and waited it out in the doorway and waited out the aftershocks."

Reporters at CNN affiliate KTVA described falling window panes at the station's offices.

"The structure of the roof just collapsed," one said. "We can't even get into our studio right now. There were computers flying, cameras toppling over."