Families have been forced out of their homes after a hillside started mysteriously swallowing them up.
Homeowners first noticed cracks in the walls and had difficulty closing doors before the 30-year-old houses started collapsing in on themselves.
The land in northern California is now so unstable that heavy machinery can not move in to carry out demolition work and mail deliveries to remaining homes have been stopped to protect postal workers.
Eight homes have been abandoned and 10 more are under notice of imminent evacuation in Lake County, about 100 miles (160km) north of San Francisco.
Scott Spivey first noticed damage to his home in March.
He said: “Doors started to not shut. Cracks in the wall started appearing. The garage door was coming off its hinges. And there were some huge cracks in the floor that we were noticing, and we could feel them even underneath the carpet.”
“It’s very painful to see your house like this, especially in this condition, especially after all the years of putting in hard work into trying to make this a really nice place.
“Doing remodelling and upgrades to appliances and to the rest of the stuff in the house. And it just seems like all the work that I put into it is just gone.”
Unlike sinkholes of Florida that can gobble homes in an instant, this collapse in hilly volcanic country can move by metres one day and just a fraction of a centimetre the next.
Officials believe water that has bubbled to the surface is playing a role in the destruction.
But nobody can explain how there is suddenly so much water on the hill in a county with groundwater shortages.
Lake County spokesman Kevin Ingram said: “Because of development on steep slopes we do see slides from time to time, but they’re always associated with storm events or something like this.
“This is really unusual and we haven’t seen anything like it.”
The Lake County Board of Supervisors has asked Governor Jerry Brown to declare an emergency so funding might be available to stabilise utilities and determine the cause of the collapse.
The California Emergency Management Agency has said Brown is still assessing the situation.