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Roadside Geology Series #19
Roadside Geology of Northern and Central California
Informative travel companions about roadside terrain and geology with photos, diagrams, and glossary.
369 pages, Paperback
First published December 1, 2000
About the author
David D. Alt
20 books3 followersDavid Alt was an American geologist, teacher, writer, storyteller and author. He was the author of more than thirty books, including several titles in the Roadside Geology series published by Mountain Press.
He earned his Ph.D. in 1961 from the University of Texas, and joined the Department of Geology at The University of Montana in Missoula, Montana in 1965. He became professor Emeritus at The University of Montana in 2002. He died on April 26, 2015, in Missoula.
He earned his Ph.D. in 1961 from the University of Texas, and joined the Department of Geology at The University of Montana in Missoula, Montana in 1965. He became professor Emeritus at The University of Montana in 2002. He died on April 26, 2015, in Missoula.
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Displaying 1 - 11 of 11 reviews
January 12, 2019
I own the earlier edition (which is just Northern Calif). If you're in the market, the latest edition is the one to get (or order from the library). These guys write well, and know their stuff. You will earn interesting stuff, regardless of your skill level and/or knowledge of geology. I'm a professional geologist, and I've seen a lot of bad or mediocre hiway guides over the years (Halka Chronic), I'm looking at you). This one is starting out GREAT.
And it's still great, two thirds (or more) through. Definitely go for the 2nd edition, with color maps & photos, is the advice of Amazon readers. I haven't seen that one (yet).
Here's my review of the older edition: https://www.goodreads.com/review/show...
And I'll also refer you to an older guidebook, "Geologic History of Middle California" (1979) https://www.goodreads.com/review/show... It's a bit out of date, but pocket size. If you find a copy for a dollar or two, or if your library still has a copy....
And it's still great, two thirds (or more) through. Definitely go for the 2nd edition, with color maps & photos, is the advice of Amazon readers. I haven't seen that one (yet).
Here's my review of the older edition: https://www.goodreads.com/review/show...
And I'll also refer you to an older guidebook, "Geologic History of Middle California" (1979) https://www.goodreads.com/review/show... It's a bit out of date, but pocket size. If you find a copy for a dollar or two, or if your library still has a copy....
April 5, 2019
I was not a fan of Alt and Hyndman's earlier books, but this 2016 second edition is easily one of my top 10 books of all time. I recognize that just saying it's perfect isn't helpful, so here's a list of things I love:
1. Scope and Sequence. The book as a whole takes on a fairly natural chunk of the earth to look at - California north of the Garlock fault. The sequence actually makes sense, broadly moving from older to younger geologic features of California.
2. Pacing. The authors use foreshadowing and repetition to emphasize the geologic features that they are examining. Something that is mentioned in passing in one section is explained in greater detail throughout the book. This is actually a powerful teaching tool (and I say that as a STEM educator) because instead of vomiting all the information in a couple of pages and never touching it again, the authors spread out the information and demonstrate why it is important because of how often it comes up.
3. Forest and Trees. The authors start every section with a broad geologic history and overview (forest) and then explore the individual road trips (trees). In addition, the literally overlapping formations and crossroads ties back into the repetition and pacing from above.
4. Images. The book is full of photos, diagrams, maps, cross-sections - everything a scientist could possibly want. And they are beautiful! Great color choices, sensible design, easy to read, aesthetically pleasing.
I love this so much more than the first edition, and I am now excited to read more of the authors' newer books. Love it, love it, love it! If you care at all about CA geology, buy this book.
1. Scope and Sequence. The book as a whole takes on a fairly natural chunk of the earth to look at - California north of the Garlock fault. The sequence actually makes sense, broadly moving from older to younger geologic features of California.
2. Pacing. The authors use foreshadowing and repetition to emphasize the geologic features that they are examining. Something that is mentioned in passing in one section is explained in greater detail throughout the book. This is actually a powerful teaching tool (and I say that as a STEM educator) because instead of vomiting all the information in a couple of pages and never touching it again, the authors spread out the information and demonstrate why it is important because of how often it comes up.
3. Forest and Trees. The authors start every section with a broad geologic history and overview (forest) and then explore the individual road trips (trees). In addition, the literally overlapping formations and crossroads ties back into the repetition and pacing from above.
4. Images. The book is full of photos, diagrams, maps, cross-sections - everything a scientist could possibly want. And they are beautiful! Great color choices, sensible design, easy to read, aesthetically pleasing.
I love this so much more than the first edition, and I am now excited to read more of the authors' newer books. Love it, love it, love it! If you care at all about CA geology, buy this book.
March 29, 2014
My corner of the world is the one where the North American continent started crashing into the Pacific plate some 180 million years ago. It's geology has been described with terms like "chaotic jumble" and "unholy mess". I recommend the entire series to anyone traveling here who wants to understand how the ground under their feet got to be the way it is. You will get a sense of groundedness that is quite satisfying. The books remind me of what good encyclopedia articles were like in the days of a stable publishing industry - knowledgeable, comprehensive and readable. This particular volume's writing style is compressed partly because of the amount of ground covered and I suspect partly because of the author's style. The relevant parts (nobody sees all of California in one go) merit several readings.
June 23, 2024
This was such a cool book. It covers the geology of Northern California at an accessible yet pleasantly excruciating level of detail. As someone who has never taken a geology course but has more than the average interest in local rocks, this was the perfect book for me. The authors' approach to this book seems to be to kind of use it as a Trojan horse to teach the reader about a lot of geological concepts, which is good for a beginner. There is a lot of repetition, which was great for me because a lot of the geological terminology was hard to remember. It also allowed me to jump around to different geological areas in the book without feeling like I had missed out on crucial information in previous chapters.
A pleasant surprise about this book is that while I was most excited about the geology of the places I've visited, it turns out that the sections on the geology of places I haven't visited (the Klamath Mountains, Modoc Plateau, and Basin and Range east of the Sierras) were even more fascinating, and I learned a lot about seemingly every nook and cranny of (the northern part of) my native state by reading this book.
The book reviews the process by which California was created, which is really fascinating. Basically none of Northern California was originally part of the North American craton/continental plate. Most of Northern California was formed by three events in which trenches on the edge of the North American plate accumulated tons of debris that got lifted into mountain ranges. Originally, the continent ended at roughly the border with Nevada hundreds of millions of years ago. At that border was a subduction zone, or trench, where a continental plate was sliding under the North American plate. Around 350 million years ago, this process of subduction caused the Antler mountain building event, during which rocky debris on the ocean floor was jammed against the North American plate, forming what is now called the Shoo Fly Complex in the eastern Sierra Nevadas (of course, this was long before the Sierras formed. At the time this debris formed its own mountain range at approximately the same location as the Sierras, I guess).
Next, 200 million years ago, a new trench, called the Sierran trench, formed as the North American plate split at what is now the mid-Atlantic ridge and began moving west, plowing over the plate west of it and crushing rocky debris onto its coast against the Shoo Fly Complex, forming what is now called the Calaveras Complex. The rocky debris included old volcanic islands (think Hawaii or Japan).
Next, probably around 130 million years ago, the Sierran trench deactivated and a new trench, called the Franciscan trench, opened up about 60 miles westward. The random decision of the ocean floor to stop subducting at the Sierran trench and to form a new trench 60 miles west is what gave us the Central Valley! Although the ground level of the Central Valley now lies on probably thousands of feet of sediment, the ultimate bedrock of the Central Valley is old sea floor that refused to subduct. Meanwhile, the subduction activity at the Franciscan trench caused volcanism further to the east, causing massive amount of granite magma to rise close to the surface (or to erupt above the surface), forming the core of what would later become the Sierra Nevadas.
The plate subducting beneath the North American plate at this time was called the Farallon plate. The eastern edge of the Farallon plate was this subduction zone; the western edge was an oceanic ridge that was producing more crust, but not at a rate fast enough to make up for the subduction in the east. As the Farallon plate got plowed over by the North American plate, eventually the trench met the ridge, and both crust-forming and crust-eating action were extinguished. The place where the ridge and trench met (and where the Pacific and North American plates now meet) is called the San Andreas fault zone; the faults in this zone do not eat or produce crust but are instead transform faults that slip laterally against each other. Interestingly, this ridge-meeting-trench extinguishing action is not finished! The Farallon plate still exists off the coast of Oregon and Washington; the subduction of the plate under Oregan and Washington is what fuels the Cascade volcanoes. However, the triple junction between the Pacific, Farallon, and North American plates is slowing zipping itself up, so that eventually the Farallon plate will disappear and the trench will be replaced by transform faults like what we have in California. With the extinction of the trench and the formation of the San Andreas fault around 30-15 million years ago, the contents of the Franciscan trench rose to become the Coast Range of California.
Lastly, within about the past 16 million years, the area between the Sierras and western Utah started to stretch, roughly doubling its east-to-west expanse. This stretching action pulled the crust apart, literally forming stretch marks - the crust split apart in roughly north-to-south lines. As this happened, each liberated chunk of crust subsided, generally in a way so that the west side sank while the east side rose. This formed a deep valley in the west and a tall mountain ridge in the east (hence Basin and Range). If you look at a topographic map of Nevada, you will notice that the entire state is dominated by this formation. The Sierra Nevadas are the westernmost of the ranges. So interestingly, until around 15 million years ago, the area where the Sierra Nevadas are today was flat and hilly. As the region of stretching/expanding crust hit that area, the crust of the Sierra Nevadas tilted up in the east. Therefore the western approach to the Sierras is relatively lightly tilted, and according to the book you can still make out vestiges of its old past as a flat and hilly landscape. Meanwhile the eastern approach to the Sierras is extremely steep and drops down into deep valleys such as Lake Tahoe and the Owens Valley. Lastly, as the Sierra Nevada rose, erosion intensified, exposing more and more of the massive granite batholith that underlies the entire region. The book points out that for whatever region, this erosional process is happening south to north, so a lot more granite is exposed in the southern Sierras than in the north; over time, more and more granite will likely be exposed. Furthermore, the Basin and Range is not yet done expanding, so it is likely that more ridges and valleys will form on the western side of the Sierras.
Given all of this cool backstory, I had high hopes for the Bay Area, which is where I live. Tragically, despite our dramatic coastal cliffs and numerous mountains, the Bay Area is basically a worst-case scenario for people who are interested in rocks. The book, which describes pretty much all of the other regions of California pretty generously, said that the Franciscan Complex, which underlies most of the Coast Range and the Bay Area, "is one of the world's grand messes." "These are rocks at their most frustrating - complicated and poorly exposed." "If all rocks resembled the Franciscan Complex, no science of bedrock geology could have emerged." "The most abundant Franciscan rock type is muddy sandstone." In terms of interesting rocks, we get one consolation prize - we have a lot of chert. Chert is formed by "siliceous ooze", which forms from the silica-rich skeletons of plankton that rain down on the ocean floor. It typically only forms in very deep parts of the ocean, where the calcium that also forms part of the skeletons of plankton gets dissolved, leaving only the silica. The siliceous ooze eventually solidifies into colorful layers of chert. When I was young, one of my most prized rocks was a rock I had found that had mysterious colorful layers. Now I'm pretty sure it was chert.
The book has some other interesting facts about the Bay Area. Most of the mountains and valleys formed in the Coast Range are caused by fault activity - there are probably thousands of faults besides just the San Andreas fault, all moving parallel to each other and at slightly different rates. If a fault has a kink in it, depending on the direction it's moving, the kink will either form a valley or a ridge. The book doesn't explain how the Santa Clara Valley itself formed, but I would guess it could have been from an especially large kink that pulled the crust apart, forming the valley.
As a denizen of the South Bay, I have to content myself with the fact that the land I live on is just sediment washed down from the neighboring hills and the Sierra Nevada. At the end of the last Ice Age, sea level was 300 feet lower. When the waters abruptly rose, basically all coastal regions were reset. Basically all coastlines in mountainous areas were simply water meeting mountain. In the ensuing thousands of years, sediments have accumulated at the new sea level, giving us beaches and, presumably, the entire South Bay.
I won't go into detail about the other regions of California, but they were basically all more interesting than the Coast Range (it's not hard to compete with a geological dump heap). But some general takeaways were that, although geology is kind of dry, and definitely not a subject of polite conversation at a party, it gives appreciators an enhanced perspective of time, change, and (im)permanence. My state of California feels permanent, but it actually used to not exist at all. Mountains are not solid blocks of stone, but rather crumbly piles of stone that haven't been eroded to nubs yet. The Monterey Peninsula, an area I have visited often, is not really a part of California - it's actually on the Pacific plate and will eventually slide off of California and become an island in the Pacific Ocean. There are still many active volcanic regions in eastern and northern California that have completed altered the landscape in the past few thousand years and will certainly do so over the next few thousand years. Even in the absence of catastrophic earthquakes, the land beneath our feet is moving - if we're lucky. Faults that slip slowly and consistently, such as the one under Hollister, don't produce large earthquakes. Unfortunately, the segment of the San Andreas fault near us is almost always stuck, so when it moves it produces a cataclysm.
The one issue with the book is that even though it's meant to be accessible to beginners, and it mostly is, it does assume some familiarity with rock types. I have no idea what feldspar or schist or plagioclase or metasedimentary rock is, and although the book may have devoted a sentence or two to describing them, I quickly forgot their definitions. Also, although the book has lots of great photos of roadcuts, I have to admit that 70% of the roadcuts all look like "rock" to me, even with the descriptions differentiating them as "greenstone", "serpentinite", "slate", "gravel", etc. I spent a lot of time researching things on Wikipedia and Google Maps, but it wasn't always enough to compensate.
A pleasant surprise about this book is that while I was most excited about the geology of the places I've visited, it turns out that the sections on the geology of places I haven't visited (the Klamath Mountains, Modoc Plateau, and Basin and Range east of the Sierras) were even more fascinating, and I learned a lot about seemingly every nook and cranny of (the northern part of) my native state by reading this book.
The book reviews the process by which California was created, which is really fascinating. Basically none of Northern California was originally part of the North American craton/continental plate. Most of Northern California was formed by three events in which trenches on the edge of the North American plate accumulated tons of debris that got lifted into mountain ranges. Originally, the continent ended at roughly the border with Nevada hundreds of millions of years ago. At that border was a subduction zone, or trench, where a continental plate was sliding under the North American plate. Around 350 million years ago, this process of subduction caused the Antler mountain building event, during which rocky debris on the ocean floor was jammed against the North American plate, forming what is now called the Shoo Fly Complex in the eastern Sierra Nevadas (of course, this was long before the Sierras formed. At the time this debris formed its own mountain range at approximately the same location as the Sierras, I guess).
Next, 200 million years ago, a new trench, called the Sierran trench, formed as the North American plate split at what is now the mid-Atlantic ridge and began moving west, plowing over the plate west of it and crushing rocky debris onto its coast against the Shoo Fly Complex, forming what is now called the Calaveras Complex. The rocky debris included old volcanic islands (think Hawaii or Japan).
Next, probably around 130 million years ago, the Sierran trench deactivated and a new trench, called the Franciscan trench, opened up about 60 miles westward. The random decision of the ocean floor to stop subducting at the Sierran trench and to form a new trench 60 miles west is what gave us the Central Valley! Although the ground level of the Central Valley now lies on probably thousands of feet of sediment, the ultimate bedrock of the Central Valley is old sea floor that refused to subduct. Meanwhile, the subduction activity at the Franciscan trench caused volcanism further to the east, causing massive amount of granite magma to rise close to the surface (or to erupt above the surface), forming the core of what would later become the Sierra Nevadas.
The plate subducting beneath the North American plate at this time was called the Farallon plate. The eastern edge of the Farallon plate was this subduction zone; the western edge was an oceanic ridge that was producing more crust, but not at a rate fast enough to make up for the subduction in the east. As the Farallon plate got plowed over by the North American plate, eventually the trench met the ridge, and both crust-forming and crust-eating action were extinguished. The place where the ridge and trench met (and where the Pacific and North American plates now meet) is called the San Andreas fault zone; the faults in this zone do not eat or produce crust but are instead transform faults that slip laterally against each other. Interestingly, this ridge-meeting-trench extinguishing action is not finished! The Farallon plate still exists off the coast of Oregon and Washington; the subduction of the plate under Oregan and Washington is what fuels the Cascade volcanoes. However, the triple junction between the Pacific, Farallon, and North American plates is slowing zipping itself up, so that eventually the Farallon plate will disappear and the trench will be replaced by transform faults like what we have in California. With the extinction of the trench and the formation of the San Andreas fault around 30-15 million years ago, the contents of the Franciscan trench rose to become the Coast Range of California.
Lastly, within about the past 16 million years, the area between the Sierras and western Utah started to stretch, roughly doubling its east-to-west expanse. This stretching action pulled the crust apart, literally forming stretch marks - the crust split apart in roughly north-to-south lines. As this happened, each liberated chunk of crust subsided, generally in a way so that the west side sank while the east side rose. This formed a deep valley in the west and a tall mountain ridge in the east (hence Basin and Range). If you look at a topographic map of Nevada, you will notice that the entire state is dominated by this formation. The Sierra Nevadas are the westernmost of the ranges. So interestingly, until around 15 million years ago, the area where the Sierra Nevadas are today was flat and hilly. As the region of stretching/expanding crust hit that area, the crust of the Sierra Nevadas tilted up in the east. Therefore the western approach to the Sierras is relatively lightly tilted, and according to the book you can still make out vestiges of its old past as a flat and hilly landscape. Meanwhile the eastern approach to the Sierras is extremely steep and drops down into deep valleys such as Lake Tahoe and the Owens Valley. Lastly, as the Sierra Nevada rose, erosion intensified, exposing more and more of the massive granite batholith that underlies the entire region. The book points out that for whatever region, this erosional process is happening south to north, so a lot more granite is exposed in the southern Sierras than in the north; over time, more and more granite will likely be exposed. Furthermore, the Basin and Range is not yet done expanding, so it is likely that more ridges and valleys will form on the western side of the Sierras.
Given all of this cool backstory, I had high hopes for the Bay Area, which is where I live. Tragically, despite our dramatic coastal cliffs and numerous mountains, the Bay Area is basically a worst-case scenario for people who are interested in rocks. The book, which describes pretty much all of the other regions of California pretty generously, said that the Franciscan Complex, which underlies most of the Coast Range and the Bay Area, "is one of the world's grand messes." "These are rocks at their most frustrating - complicated and poorly exposed." "If all rocks resembled the Franciscan Complex, no science of bedrock geology could have emerged." "The most abundant Franciscan rock type is muddy sandstone." In terms of interesting rocks, we get one consolation prize - we have a lot of chert. Chert is formed by "siliceous ooze", which forms from the silica-rich skeletons of plankton that rain down on the ocean floor. It typically only forms in very deep parts of the ocean, where the calcium that also forms part of the skeletons of plankton gets dissolved, leaving only the silica. The siliceous ooze eventually solidifies into colorful layers of chert. When I was young, one of my most prized rocks was a rock I had found that had mysterious colorful layers. Now I'm pretty sure it was chert.
The book has some other interesting facts about the Bay Area. Most of the mountains and valleys formed in the Coast Range are caused by fault activity - there are probably thousands of faults besides just the San Andreas fault, all moving parallel to each other and at slightly different rates. If a fault has a kink in it, depending on the direction it's moving, the kink will either form a valley or a ridge. The book doesn't explain how the Santa Clara Valley itself formed, but I would guess it could have been from an especially large kink that pulled the crust apart, forming the valley.
As a denizen of the South Bay, I have to content myself with the fact that the land I live on is just sediment washed down from the neighboring hills and the Sierra Nevada. At the end of the last Ice Age, sea level was 300 feet lower. When the waters abruptly rose, basically all coastal regions were reset. Basically all coastlines in mountainous areas were simply water meeting mountain. In the ensuing thousands of years, sediments have accumulated at the new sea level, giving us beaches and, presumably, the entire South Bay.
I won't go into detail about the other regions of California, but they were basically all more interesting than the Coast Range (it's not hard to compete with a geological dump heap). But some general takeaways were that, although geology is kind of dry, and definitely not a subject of polite conversation at a party, it gives appreciators an enhanced perspective of time, change, and (im)permanence. My state of California feels permanent, but it actually used to not exist at all. Mountains are not solid blocks of stone, but rather crumbly piles of stone that haven't been eroded to nubs yet. The Monterey Peninsula, an area I have visited often, is not really a part of California - it's actually on the Pacific plate and will eventually slide off of California and become an island in the Pacific Ocean. There are still many active volcanic regions in eastern and northern California that have completed altered the landscape in the past few thousand years and will certainly do so over the next few thousand years. Even in the absence of catastrophic earthquakes, the land beneath our feet is moving - if we're lucky. Faults that slip slowly and consistently, such as the one under Hollister, don't produce large earthquakes. Unfortunately, the segment of the San Andreas fault near us is almost always stuck, so when it moves it produces a cataclysm.
The one issue with the book is that even though it's meant to be accessible to beginners, and it mostly is, it does assume some familiarity with rock types. I have no idea what feldspar or schist or plagioclase or metasedimentary rock is, and although the book may have devoted a sentence or two to describing them, I quickly forgot their definitions. Also, although the book has lots of great photos of roadcuts, I have to admit that 70% of the roadcuts all look like "rock" to me, even with the descriptions differentiating them as "greenstone", "serpentinite", "slate", "gravel", etc. I spent a lot of time researching things on Wikipedia and Google Maps, but it wasn't always enough to compensate.
August 19, 2008
Great series, but they completely left out huge chuncks of the 395 corridor on the Eastern side of the Sierra Nevadas. Really disappointed in the vague descriptions of this area. They also left out the Bridgeport area. Very disappointed if that's the area of your travel. Compare your trip with the contents before buying.
January 17, 2012
Fun to read while driving through California on vacation. You can learn about the faults, rock formations, mountain ranges etc as you drive--things you can see from the car window. Gives you driving routes to follow from place to place if you want.
February 16, 2020
For Northern Californians, there is simply no better book to keep in your car. For this reason, I own 2 copies.
The photos here are black and white, and could use updating in a future revision. The Socal version has much higher quality maps, photos and graphics. Nevertheless, an absolute classic.
The photos here are black and white, and could use updating in a future revision. The Socal version has much higher quality maps, photos and graphics. Nevertheless, an absolute classic.
October 14, 2023
This book is chalked full (get it 😉) of information about the rocks and different areas of northern California. It is very informative, well written and easy to read. It's really nice as a companion book to a road trip.
June 5, 2022
tells about Santa Maria
Want to Read
June 19, 2010I am on a quest to understand the complex geology of California. Here's hoping.
Read
March 15, 2015I registered a book at BookCrossing.com!
http://www.BookCrossing.com/journal/12299135
http://www.BookCrossing.com/journal/12299135
Displaying 1 - 11 of 11 reviews