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Local California government accidentally destroys geological marvel

A local California government destroyed a geological marvel, without even knowing it.

For years, geologists, science classes, and "geopilgrims" ventured to a split in a sidewalk curb in Hayward, California. Two sections of sidewalk have been slowing drifting askew for several decades, creating a striking visual portrayal of something geologists call creep.

The curb sits on the Hayward fault, one of seven significant faults in the San Francisco Bay area. It runs nearly parallel to the more famous San Andreas fault, and is considered part of that "fault system." The system forms the boundary of the North American and Pacific plates.

Creep is the slow steady movement of earth along the fault, in different directions. Unlike earthquakes, creep is seismic movement that is so slow and subtle, it is typically not felt. But it shows up in structures made by humans, such as concrete roads and buildings, which are too brittle to adapt to the slow movement of the ground below.

When it was first made, the curb formed a solid straight line. But over time, the curb split, with one end drifting south, and the western side drifting north, according to the Los Angeles Times.

But now it is gone. The city of Hayward removed the offset curb, which lies at an intersection, to make way for a wheelchair accessible ramp.

One geologist from the United States Geological Survey told the LA Times is it was "an iconic location on the Hayward fault."

But apparently, city officials were unaware of the curb's significance to geologists and science buffs.

Had they known of its significance, assistant city manager Kelly McAdoo told the paper, the city "probably would have looked at it differently, or we would have tried to help them document it."

Pictures of the curb throughout the years can be seen on United States Geological Survey web pages, and there is a gallery of photos of the curb in the 1970s on the website of former California State University geology professor Sue Ellen Hirschfield, who now gives local geological walking tours in the area.

A USGS-led report in 2008 noted that the Hayward fault is one of two (along with the nearby Rodgers Creek fault) most likely to produce a severe earthquake in the Bay Area. The Hayward fault was responsible for a magnitude 6.8 earthquake in the region in 1868 that killed about 30 people. One occurring today would likely cause far greater damage as it is a far more heavily populated and developed region.

USGS research observed that the five large earthquakes along the fault have occurred 140 years apart, meaning that another one could occur at any time. When a magnitiude 4.0 earthquake struck along the fault in 2015, a USGS scientist Tom Brocher reiterated that warning, saying the population of the area is now 100 times what it was in 1868.