The area I live in used to be covered in oil wells until the 1940's or so. Just south of where I live there is an open tar pit, the La Brea tar pit, which I visited last year.
I'd heard that sometimes oil bubbles out to the surface around the neighborhood, but I'd never seen it before. This is a sidewalk on Curson Ave., near the tar pits, in mid-January. It's actively oozing:
This one below was recently oozing, you can see a soft spot at the upper left. It's at the intersection of Curson and Wilshire:
Jed Clampett would feel right at home.