The Root of the Matter

Looking at our ragged, gorgeous San Gabriels is like looking at someone beautiful treading water--nice on top but murky underneath. That is, until now.

UCLA researcher Monica Kohler has tapped the imaging powers of earthquake waves to come up with the first picture of the San Gabriel Mountains’ root. “I am looking at features in the earth we’ll never be able to dig a hole down to, at least not in our lifetime,” says Kohler. “It’s really exciting.”

The root is about 25 miles deep, six more than many geophysicists thought, and about double the thickness, Kohler believes, of the skinny crust beneath the L.A. Basin. It stretches from the northernmost San Gabriel Valley to the southernmost Mojave Desert, from Azusa to Lancaster.

The mountains are pinkish-white granitic-type rock from their peaks down to where they squeeze against the hard green and black rocks of the mantle. And they get deeper and higher with every rattle of the northern end of the L.A. basin. In tens of millions of years they could top the Himalayas. If only researchers could figure out how to shut down the aging process, so we can hang around and watch the San Gabriels grow