Where Two Mountain Ranges Collide — Sylmar

As the freeways braid together around you here at Sylmar, you're sitting in a seam. To the west the Santa Susana Mountains rise; to the east the San Gabriels climb toward their 4,000-foot western edge. They don't so much merge as crowd into each other, pressed together as the crust folds and faults under the strain of the same compression that builds all of Southern California's ranges. Both are still rising. The valley floor beneath you — the Sylmar basin — is sinking at the same time, downfolded as the mountains squeeze in. It is some of the most seismically restless ground in the region, and the history here proves it.

At 6:00 on the morning of February 9, 1971, that strain let go. The magnitude-6.6 San Fernando quake — known locally as the Sylmar quake — ruptured the fault zone just east of here. Newly built freeway connectors at this very interchange pancaked to the ground, killing two men in a pickup. A Veterans hospital collapsed; the Lower Van Norman Dam nearly failed, forcing 80,000 people from their homes. The disaster rewrote California law, giving us fault-zone building limits and tougher dam-safety rules. Then, in January 1994, the Northridge quake toppled a connector here again, killing LAPD officer Clarence Wayne Dean — for whom the interchange is now named.

Long before the concrete, this was a sycamore-and-oak country of the Fernandeño Tataviam, whose villages ringed these foothills before Mission San Fernando was founded nearby in 1797. The name Sylmar itself comes from Latin for "sea of trees" — for the vast olive groves that once blanketed these slopes, briefly the largest olive orchard on earth. A sea of trees, on ground that will not hold still.