Mountains: The Cascades

Mountains: The Cascades

The Cascade Mountain range stretches across much of the West Coast, providing beautiful scenery and many recreation opportunities.

For Earth scientists, the Cascade Mountains are one of the most important features in our state. Why?

The Cascades are so important because they are a significant example of the role of plate tectonics in shaping California millions of years ago.

Also known as the Cascadia subduction zone, these mountains were formed by the constant movement of tectonic plates in the lithosphere.

An ancient tectonic plate called the Farallon plate formed a convergent boundary with the North American plate, starting in Northern California.

Because the Farallon plate was a denser oceanic plate, when it came together with the continental North American plate, the Farallon gradually sank.

As the Farallon plate sank, it partially melted because of contact with the heat of the mantle. Magma (very hot rock) from this melting began to rise to the upper layers of the Earth.

Through this process, many volcanoes formed in the Cascade Range, including Mount Shasta, Lassen Peak, and Mount St. Helen’s.

This convergent boundary was so active that the Farallon plate eventually sank completely under the North American plate. Therefore, the Farallon plate does not exist today!

Earthquakes: The 1989 Loma Prieta Earthquake

Earthquakes: The 1989 Loma Prieta Earthquake

Even though it wasn’t an extremely large earthquake, the Loma Prieta earthquake made a big impact in the Bay Area.

Because the 1906 San Francisco earthquake had been so terrible, places built here after it had to be made earthquake-safe.

But some of these “safe” buildings collapsed or were damaged in the 1989 earthquake, showing people in the Bay Area that more had to be done to prepare for an emergency.

And the damage did not just happened in poor areas, or in areas where not very many people lived. Cities and communities across the Bay Area were affected.

In fact, the Bay Bridge – the biggest transportation hub in the Bay Area – was damaged. Local leaders took the threat of an earthquake so seriously that they just finished making it more earthquake-safe last year (more than 20 years later).

These effects made Bay Area residents re-consider what is truly earthquake-safe. It also made them consider emergency preparedness as a priority again.

And in this way, the Loma Prieta Earthquake affected the Bay Area positively, despite all the physical damage.

Earthquakes: The 1994 Northridge Earthquake

  



Earthquakes: The 1994 Northridge Earthquake

The Northridge earthquake is significant because it is the most recent earthquake to occur in the San Fernando Valley. And more importantly, it was the costliest (most expensive) earthquake ever in the United States.

Even though this city environment was built to stay standing even in the worst earthquake, the 1994 quake showed that there was still a lot of room for improvement.

Some buildings collapsed or damaged, and some even caught on fire. This showed people living in the San Fernando Valley that even the earthquake-safe buildings were not safe enough.

As the city recovered and rebuilt freeways, parking structures, and buildings, they decided to make buildings even safer. They did this using new technology and stronger materials.

The city got safer in other ways too. Now, schools and public organizations are required to do earthquake drills so that people will know what to do in an emergency.

And police, fire fighters, and emergency medical workers are trained in emergency preparedness (being prepared for an emergency).

All of this has helped make Los Angeles a safer place should another earthquake occur here!