Residents in Coupeville on Whidbey Island reported hearing a noise that sounded like rumbling thunder just after 4 a.m. on Wednesday as the land began to give way.
As hundreds of feet of earth slid from the edge of the island's bluff, one house was knocked off its foundation and a road was destroyed, which left 16 homes isolated.
Another 17 homes on an uphill road are also threatened by the mudslide, which authorities have warned is still moving. It was within 10 feet of a home late on Wednesday morning.
'It's possible more homes could be lost. We're trying to ensure the safety and awareness of people,' Central Whidbey Fire and Rescue Chief Ed Hartin. 'There's not anything we can do to stop the movement of the ground.'
Officials said the slide broke across 400 to 500 yards on the hillside and downhill 600 or 700 yards to the water.
Authorities said no one was hurt, but that a resident in the destroyed home had a pre-existing medical condition and was taken to the local hospital.
Officials warned that the ground is continuing to slide and the area will be isolated for the 'foreseeable future'.
'It's massive. I wouldn't even put a description on it,' Chad Michael, assistant chief of Central Whidbey Fire and Rescue, told the Whidbey News Times.
Island County Sheriff Mark Brown said he did not know what sparked the massive slide, as there had been no rain before the land began to give way. But the area has been prone to slides in the past.
'It must have just been moisture in the ground that accumulated,' he told KOMO.
The News Times noted that the affected area looked at least the size of two football fields.
Residents continue to be evacuated and a relief center for the dozen of residents displaced by the landslide has been set up at a nearby community center.
Three people had to be evacuated on an all terrain vehicle and ten people had to be taken out by boat, officials said.
Those living in threatened homes could be seen walking to the edge of the cliff this morning to see just how close to the edge their properties were teetering.
Ahead of them was a massive drop strewn with mud and debris, as well as downed trees and the remnants of a coastal home.
Resident Bret Holmes told the News Times that he has been losing ground at his property all morning; there was previously more than 30 feet of land to the bluff's edge but now there is just 15.
He said the land started to give way after he heard what he described as 'a sonic boom'.
'I heard something loud, looked out my window and noticed I didn't have any trees in the front yard anymore,' he said.
A geotechnical engineer will arrive at the site this afternoon, which will give residents more of an idea of when they can return to their homes, officials said.
'The road's been cut off, the power's been cut off and the water's been cut off to the homes on the beach,' Island County Sheriff Mark Brown said.
Island County Commissioner Helen Price Johnson visited the area to see the devastation.
'It's a tragic loss for these property owners and this community,' she told the News Times. 'We just need to pull together.'