City workers in Hayward, California have accidentally destroyed a slice of sidewalk that for years has acted as an ideal indicator of the tectonic shifts taking place under the state. The curb at the corner of Rose and Prospect sat right across California's Hayward fault, and became a site of pilgrimage for seismologists and geologists over the year, its growing offset showing how the street — and the state — was being pulled apart by the movements of the Earth's crust. But Hayward's city council didn't see the geological feature, looking at the curb instead as a piece of broken road, and replacing it without warning in June.

"This is just devastating news," the US Geological Survey's Ken Hudnut said, with Andrew Alden — an Oakland science writer — echoing his views. "It's sad. It was a real letdown," Alden wrote in a blog post. "It's really unusual to have such a clean piece of evidence right here." Scientists are only left with photos that document the creep of the curb over the years, showing an offset of just a few inches in 1971, all the way to earlier this year when the gap was wider than the curb itself.

Bad news: the Rose/Prospect curb is gone after 45 years of recording Hayward fault creep pic.twitter.com/O4GwiURrHB — Andrew Alden (@aboutgeology) June 24, 2016

But despite all this interest in the Hayward curb, apparently nobody in the scientific community thought to notify the city. "We probably would have looked at it differently, or we would have tried to help them document it," assistant city manager Kelly McAdoo said when informed about the curb's significance. "Our mandate from our council is that we have safe sidewalks and accessible sidewalks for all members of our community," McAdoo told the LA Times, explaining that the curb was replaced with a wheelchair-accessible ramp. Even if the scientists had let the city know, McAdoo says that it still might have been removed. "When you've got a curb that's offset, we probably would eventually want to fix it and see if there's some other way to monitor seismic safety over time."

The same plate movement that was causing the earth to move under the curb is expected to be the cause of a large earthquake soon. Scientists say the Hayward fault produces a significant quake every 160 years, with a margin of error of 80 years, and it's been a century-and-a-half since the last one. Fortunately, while the Hayward curb was a neat and very visual indicator of the fault under the city, seismologists have many more scientific ways to track upcoming earthquakes than staring intently at a piece of slowly moving sidewalk.