1: Introduction to the Geology of California

Why California Geology?

California’s geology is so rich, so diverse, so dynamic that one could conceivably see almost every type of rock and mineral, every type of volcano, every type of fault, every type of climate and water system, without leaving the boundaries of the Golden State.

Travel is, of course, a virtue and a necessity for a well-rounded life; as Twain wrote in Innocents Abroad, “Travel is fatal to prejudice, bigotry and narrow-mindedness.” But to experience virtually everything in geology, California by itself is an open-air textbook of the Earth.

Glacially-carved landscapes with three thousand foot cliffs? Yosemite. Boiling mud lakes reeking of sulfur, heated and supplied from an ancient volcano that blew itself apart? Lassen. Mysterious dolomite boulders moving and plowing through the soil of a vast dry lake bed? Death Valley. Giant lava flows with endless miles of underground lava tubes? Lava Beds National Monument. The fault scarp of a plate boundary extending as far as you can see? The Carrizo Plain in the Great Valley. Fossils from the dawn of animal life? White Mountains. Rugged coastlines with mountains that touch the sea? Big Sur. Glassy domes of obsidian rising out of a vast lake created by accident? Salton Sea. California has all this and much more. 

Other states have fascinating geology too. Kick any rock in any stream in Missouri and it probably is chock-full of mollusk fossils from when the whole of the Midwest was under a vast inland ocean. People walk miles along the southern coast of the Big Island of Hawaii to witness yellow-orange lava spilling into the hissing waves of the Pacific. 

But California has a unique range of amazing geologic features, concentrated between parched deserts and freezing glaciers, between fault-crushed hills and river-carved canyons, between the highest point in the contiguous United States (Mt. Whitney, Figure 1.1) and the lowest point in the contiguous United States (Badwater, Death Valley).

We write this book because this is a place we love and when you love something, you want to share it with the world.

Who it is for

This textbook was designed to accommodate diverse backgrounds and learning needs among students enrolling in California Geology courses. It caters to both those with prior geology education and those without, allowing instructors to adapt the material to their particular course.

To ensure inclusivity, the book begins with foundational concepts such as minerals, rocks, plate tectonics, geologic structures, and seismology, assuming no prior geology knowledge. This approach facilitates the onboarding of new learners while enabling experienced students to refresh their understanding of core concepts.

Additionally, the book prioritizes accessibility of the material for students. All elements, including text, images, videos, and interactive activities, have been carefully crafted and curated to be compatible with assistive technology such as screen readers. We invite you to read more about our approach to accessibility.

Why This OER was Written

This book was written to offer geology students and instructors at California Community Colleges and four-year institutions across California a text that was:

• Low cost
• Online
• Accessible and
• Openly licensed 

Though excellent traditional textbooks for California Geology courses existed at the time that this book was written (e.g. California Geology by Deborah R. Harden, California’s Amazing Geology by Donald R. Prothero), there were few low-cost (<$60) or online textbook options (e.g. Mira Costa College’s online geology books by Phil Stofer). This book is freely available to anyone who wishes to learn from it. Its online format makes it easy to access from any device.

This text meets the accessibility requirements of the Academic Senate of California Community Colleges Open Educational Resource Initiative allowing as many students as possible to perceive the information.

The text is licensed under a Creative Commons Attribution Non-Commercial license (CC BY-NC) meaning it can be shared and adapted so long as it is not used for commercial purposes. 

Finally, we wrote this book to be adaptable. In our years of teaching experience we have come to understand the various different approaches instructors might take to teaching a California Geology course. For that reason, the format of this text allows instructors to change the order of chapters, and add or remove content as they see fit, while meeting all of the requirements of C-ID GEOL 200 for Geology of California.

Why Organize by Geomorphic Province?

Like a Pleistocene saber cat trying to devour a whole Columbian mammoth stuck in what would become Los Angeles’ La Brea Tar pits, our Golden State is simply too huge to digest all at once and needs to be bitten into smaller pieces. California’s size warrants parsing in some meaningful way.

California’s geomorphic provinces were first identified by California’s Chief Geologist Olaf Jenkins when he first published the Geomorphic Map of California in 1938. The 11 provinces that Jenkins identified then have gone mostly unchanged since that time. We follow this same organization, although two chapters combine multiple provinces for the purposes of brevity; These are the Cascade Range and Modoc Plateau, and the Colorado and Mojave deserts.

Accessibility of the Geosciences

There are many aspects of the geology discipline that are inherently inaccessible. Complex maps, detailed figures, and rock and mineral samples are difficult to describe fully to those who cannot perceive them. Geology students must keenly distinguish very similar colors when studying minerals and rocks, and this is a real problem for those with color blindness. Field locations are difficult to access for those with mobility limitations; in fact, the traditional capstone undergraduate course for geology majors, Field Camp, has historically required not only full mobility, but also a high level of aerobic fitness and tolerance of sometimes extreme elevation and temperature conditions, and is therefore not accessible to many students, in the same way that playing on college football teams is not accessible to all students.*

We would like a different, more open approach to the variety of college students who can engage with California’s geology – a book for everyone.

Future Work and a Call to Action

While new geology OER are being produced, there is still more we as a community of scientists and educators can do to increase the accessibility of the geoscience disciplines: 

1. Field trips are often a core component of an undergraduate degree in geology. The authors of this book look forward to contributing a collection of openly licensed field guides to lower the barrier to teaching and learning geology in the field. 
2. There is a great need for openly licensed ancillary materials such as figures, maps, and homework problems. Here are some recommendations for sharing your creative and scientific work using Creative Commons licensing so that it can be included in projects like this one and enhance student learning.
3. The recent move toward Open Access scientific journals allows that work to be accessed by anyone and shared under a Creative Commons license. It also allows figures from these works to be included in OER like this one. We fully support the movement toward Open Access scientific literature. 

We will also continue to expand this repository of ancillary materials for educators.

*We do wish to acknowledge the enormous efforts within the geoscience community to make these field experiences more inclusive. Notably, the GeoSPACE Project and the International Association for Geoscience Diversity (IAGD). 

Thumbnail: A highway sign that reads "Welcome to California". This work by Famartin via Wikimedia Commons is licensed under CC BY-SA.