They are one of the fastest-growing mountain ranges in the world. They are young, barely adolescent by geologic reckoning. Uplifted by the head-on collision of tectonic plates, the San Gabriel Mountains rest at a menacing steepness that periodically unleashes rivers of rock and mud into the subdivisions that nestle in its alluvial fans.
The range's natural architecture is fire-friendly: Row after row of canyons and narrow clefts act as chimneys, funneling flames to the high ridges, where winds launch the fire into the Los Angeles Basin to the south or the Santa Clarita Valley to the north. The sparsely vegetated slopes that are daunting for hikers are equally challenging for firefighters who can scarcely stand upright on the mountain flanks.
These are not the iconic Sierra, or the charismatic Rockies. The San Gabriels are drab, unassuming and somewhat taken for granted. But they are powerful: capable of devastating slides, particularly when winter rains follow fires.
In the last week, more than 120,000 acres have burned up and down the San Gabriel range, seemingly indifferent to the efforts of thousands of firefighters and a squadron of airplanes and helicopters. Southern Californians are taking respectful notice of what one ecologist calls the backdrop of Los Angeles.
"The San Gabriels are some of the most treacherous mountains in California and, I would argue, the American West in which to fight fire," said Char Miller, director of the environmental analysis program at Pomona College. "No one wants to fight fire in the Angeles National Forest and nobody really can, unless it's at a remove. You have these incredibly steep canyons with dense growth. A tinderbox. You have enormous amounts of fuel in some of the most inaccessible and difficult terrain possible.
"Match that up with the fact that you've got 17 to 20 million people who live in and around those canyons and foothills and it's a recipe for disaster. That's what makes the Station fire so unnerving. The fire has moved across space so easily. If the winds would have been different, this would have been an unmitigated disaster."
The San Gabriels are the result of the Pacific and North American plates slamming into each other at the spot where the San Andreas Fault takes an unusual turn. That collision is continuing: The western end of the San Gabriels was thrust up 6 1/2 feet during the 1971 Sylmar earthquake.
