The Real Jurassic Park: Why a Highway Widening Project Hasn't Been Entirely Bad for L.A.

The highway widening project that's slowed traffic along the already slothful 405 freeway for the past four years, and brought us the revelatory event known as "Carmageddon", hasn't been all bad news. It offers a glimpse of the city's oldest rocks.

1 minute read

August 23, 2013, 12:00 PM PDT

By Jonathan Nettler @nettsj


"If you’re among the 300,000 or so commuters who crawl through the Sepulveda Pass every day, you’ve surely noticed the $950-million construction project that is adding an extra lane to both sides of the 405 Freeway. You’ve no doubt spied the giant earthmovers slicing through the mountain. And at some point your gaze has rested on the eight-story-tall retaining walls doing their best to hold back the Santa Monica Mountains."

"Although expensive, inconvenient, and (some argue) unnecessary, those new cuts through the mountains thrill me," writes Arthur G. Sylvester. "I’m a geologist, and the massive expansion project has given me a temporary glimpse into the very anatomy of this mountain range that bisects Los Angeles, separating West L.A. from the Valley, downtown from Burbank. You may not know it by looking at the sleek cars streaming over the pass or the helicopters beating overhead, but the last time some of these rocks touched air, dinosaurs walked the Earth."

Monday, August 12, 2013 in Zocalo Public Square

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Wastewater pouring out from a pipe.

Alabama: Trump Terminates Settlements for Black Communities Harmed By Raw Sewage

Trump deemed the landmark civil rights agreement “illegal DEI and environmental justice policy.”

April 13, 2025 - Inside Climate News

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

April 16, 2025 - Diana Ionescu

Blue and white Seattle Link light rail train exiting concrete Downtown Bellevue Tunnel in Bellevue, WA.

Why Should We Subsidize Public Transportation?

Many public transit agencies face financial stress due to rising costs, declining fare revenue, and declining subsidies. Transit advocates must provide a strong business case for increasing public transit funding.

April 7, 2025 - Todd Litman

Two people on bikes in red painted bike lane with bus in traffic lane next to them.

Understanding Road Diets

An explainer from Momentum highlights the advantages of reducing vehicle lanes in favor of more bike, transit, and pedestrian infrastructure.

April 17 - Momentum Magazine

Aerial view of large warehouses across from development of suburban single-family homes in Jurupa, California with desert mountains in background.

New California Law Regulates Warehouse Pollution

A new law tightens building and emissions regulations for large distribution warehouses to mitigate air pollution and traffic in surrounding communities.

April 17 - Black Voice News

Purple Phoenix light rail train connected to overhead wires at sunset.

Phoenix Announces Opening Date for Light Rail Extension

The South Central extension will connect South Phoenix to downtown and other major hubs starting on June 7.

April 17 - Arizona Republic