Parts of California wine country are constantly moving northwestward.
The San Andreas Fault, a sliding boundary between two tectonic plates, extends more than 700 miles from Mexico up through western California, running offshore near the northern California town of Eureka. The plates are constantly in motion—causing parts of California wine country to move very slowly northward at a rate of a couple of inches per year—about the same rate that fingernails grow. The continual rubbing of the Pacific Plate to the west and the North American Plate to the east are responsible for some 10,000 (mostly minor) earthquakes a year. Several California wine valleys lie directly on or near the fault line.