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Northwest Exposures: A Geologic Story of the Northwest
The tale of the Northwest's geology began more than two billion years ago when an ancient continent split, creating oceanfront property in what is now western Idaho. Pacific islands mashed into that coastline, making large parts of Washington and Oregon. These events were followed by monstrous volcanic eruptions, catastrophic ice age floods, and mountains rising to an accompaniment of earthquakes.
- GenresGeologyScienceNonfiction
443 pages, Paperback
First published October 1, 1995
3 people are currently reading
42 people want to read
About the author
David D. Alt
19 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 - 5 of 5 reviews
January 3, 2021
I definitely have mixed feelings about this book.
Pros:
1. The book is very careful to cover every single unique formation in the Northwest region, from Montana to BC. Each formation gets its own colorful, narrative account of what it is and how it came to be, along with a clear map and pictures.
2. Speaking of maps and pictures, this book does not skimp - ink costs be damned! Every single feature and formation that is even briefly mentioned gets clear maps, photos, and diagrams showing what it looks like and how it formed. This helped clarify a lot of the geologic features unique to the region.
Cons:
1. Analogies. The authors are fond of analogies, and sometimes they are hits. Two examples from the same page are
-"Continents and oceanic sediments refuse to sink into the earth's interior for precisely the same reason that the marshmallow refuses to sink into a cup of hot cocoa" to describe how ophiolites form; and "
-It simply changes into hot and soft rock in the same way that a hard lump of cold wax or modeling clay softens in the warmth of you hand" to describe how solid rock becomes heated and can flow (66).
However, many times the analogies are, to put it mildly, weird.
-"Building a raft out of more or less waterlogged driftwood may well be an essential part of childhood" (218) - what kind of childhood did you people have?
-"The effect of carrying the continental crust across the mantle plume is a bit like that of dragging a blanket across the top of your extend thumb" (281) - is this how you entertain yourself before you fall asleep?
- "How, exactly, would the continental crust stretch? Some geologists imagine it behaving like a sack of dead fish" (176). Really? This was supposed to be relatable imagery for your audience? Why would anybody ever carry around a sack of dead fish? And this isn't a one-off comment, oh no, it goes on:
- "They picture gently curving and nearly horizontal faults breaking the continetal crust into big pieces shaped about like fish that slip past each other as some of the faults move. As fault movement continues, some of the fish near the surface sink and others rise as they all pull away from each other. In that view, the rocks enclosed with the Newport fault are a sinking fish. Where are the rising fish?" (176). The next section, naturally, is about "rising fish".
2. Unscientific stuff. There are small things like making repeated references to anticlines without ever actually explaining what this geologic structure is. But the most egregious is attributing the Mid-Miocene Disruption/extinction event to a supposed asteroid.
The background is that in the Middle Miocene, there were a series of flood basalt eruptions in the Pacific Northwest called the Columbia River Basalt Group (not a name that the authors use, more on that later). There was also a widespread extinction event. For some reason, the authors believe that both were caused by an asteroid impact. Aside from the screwy mechanics of how an asteroid is causing millions of years of volcanism, there is the more basic issue that this is unscientific - there is 0 evidence for it. That is evident in the language that they use:
- "For reasons that will emerge, we think the asteroid struck near the southeastern corner of Oregon" (236). Ah, I see, so there is no actual crater and you are just guessing?
- On comparison with the clear, global K-T boundary: "Nor has any middle Miocene deposit comparable to the terminal Cretaceous boundary clay been found" (236). OK, so not even circumstantial evidence, like the type that led Walter Alvarez to consider an asteroid for the K-T?
- "Many geologists imagine plumes of hot rock rising from the base of the earth's mantle to melt the upper mangle, generating huge volumes of basalt magma. We agree that mantle plumes exist, but do not suppose that they rise all the way from the earth's core. They melting that would certainly result from excavation of an enormous crater by asteroid impact seems sufficient cause" (238). Ok, this is stupid for so many reasons.
1. So the mantle plumes are not good enough to cause rock to flow, but 1 asteroid will cause 3 million years of volcanism?
2. Hmm, so the K-T extinction, you know, the one with the actual crater and shocked quartz and iridium and all the evidence for an asteroid you could want, somehow failed to produce any volcanism near the impact site, but you are expecting this comparatively small, minor asteroid to produce volcanism (again, for 3 million years)?
3. On page 268 they acknowledge hotspot volcanism in the region. Would it not be more parsimonious to blame flood basalts on the hotspot that they just acknowledged is there?
- "The impact of 17 million years ago was considerably smaller than the one that created the much larger Deccan flood basalt province of India" (238). The Deccan Traps started before the Chicxulub volcano, and even 66 MYA were still on the other side of the planet from Mexico.
- To explain flood basalts in British Columbia: "Perhaps two asteroids struck our region one terrible afternoon 17 million years ago, a big one with a smaller companion" (253). Sure, go ahead, just attribute every geologic question to asteroids. You need 2 asteroids with zero evidence? OK, why not make it 3? Or 10? How many do you want?
This bothers me because not only is the science absurd, but there is no evidence anywhere. As indicated in my quotes above, the authors have no deposits, no geologic evidence, no impact crater. This is all unsubstantiated hearsay, the book version of conspiracy videos on YouTube or the History Channel. It's a 20-page section in a 400 page book, but it really damages the credibility of the authors as scientific guides to anything.
3. The flipside of the focus on every formation is that the authors often fail to see the forest for the trees. There is often little context to the broader historical trends or to what is happening globally, which makes it harder to understand what the geologic formations mean - it is like getting a description of every individual piece of a jigsaw puzzle but never seeing how they fit together. I can demonstrate the issue with 3 maps - the first map of the entire Northwest region appears on page 298; the first map of (most) of North America appears on 328; and the first time-series map showing plate movements appears on page 404 in the epilogue.
Pros:
1. The book is very careful to cover every single unique formation in the Northwest region, from Montana to BC. Each formation gets its own colorful, narrative account of what it is and how it came to be, along with a clear map and pictures.
2. Speaking of maps and pictures, this book does not skimp - ink costs be damned! Every single feature and formation that is even briefly mentioned gets clear maps, photos, and diagrams showing what it looks like and how it formed. This helped clarify a lot of the geologic features unique to the region.
Cons:
1. Analogies. The authors are fond of analogies, and sometimes they are hits. Two examples from the same page are
-"Continents and oceanic sediments refuse to sink into the earth's interior for precisely the same reason that the marshmallow refuses to sink into a cup of hot cocoa" to describe how ophiolites form; and "
-It simply changes into hot and soft rock in the same way that a hard lump of cold wax or modeling clay softens in the warmth of you hand" to describe how solid rock becomes heated and can flow (66).
However, many times the analogies are, to put it mildly, weird.
-"Building a raft out of more or less waterlogged driftwood may well be an essential part of childhood" (218) - what kind of childhood did you people have?
-"The effect of carrying the continental crust across the mantle plume is a bit like that of dragging a blanket across the top of your extend thumb" (281) - is this how you entertain yourself before you fall asleep?
- "How, exactly, would the continental crust stretch? Some geologists imagine it behaving like a sack of dead fish" (176). Really? This was supposed to be relatable imagery for your audience? Why would anybody ever carry around a sack of dead fish? And this isn't a one-off comment, oh no, it goes on:
- "They picture gently curving and nearly horizontal faults breaking the continetal crust into big pieces shaped about like fish that slip past each other as some of the faults move. As fault movement continues, some of the fish near the surface sink and others rise as they all pull away from each other. In that view, the rocks enclosed with the Newport fault are a sinking fish. Where are the rising fish?" (176). The next section, naturally, is about "rising fish".
2. Unscientific stuff. There are small things like making repeated references to anticlines without ever actually explaining what this geologic structure is. But the most egregious is attributing the Mid-Miocene Disruption/extinction event to a supposed asteroid.
The background is that in the Middle Miocene, there were a series of flood basalt eruptions in the Pacific Northwest called the Columbia River Basalt Group (not a name that the authors use, more on that later). There was also a widespread extinction event. For some reason, the authors believe that both were caused by an asteroid impact. Aside from the screwy mechanics of how an asteroid is causing millions of years of volcanism, there is the more basic issue that this is unscientific - there is 0 evidence for it. That is evident in the language that they use:
- "For reasons that will emerge, we think the asteroid struck near the southeastern corner of Oregon" (236). Ah, I see, so there is no actual crater and you are just guessing?
- On comparison with the clear, global K-T boundary: "Nor has any middle Miocene deposit comparable to the terminal Cretaceous boundary clay been found" (236). OK, so not even circumstantial evidence, like the type that led Walter Alvarez to consider an asteroid for the K-T?
- "Many geologists imagine plumes of hot rock rising from the base of the earth's mantle to melt the upper mangle, generating huge volumes of basalt magma. We agree that mantle plumes exist, but do not suppose that they rise all the way from the earth's core. They melting that would certainly result from excavation of an enormous crater by asteroid impact seems sufficient cause" (238). Ok, this is stupid for so many reasons.
1. So the mantle plumes are not good enough to cause rock to flow, but 1 asteroid will cause 3 million years of volcanism?
2. Hmm, so the K-T extinction, you know, the one with the actual crater and shocked quartz and iridium and all the evidence for an asteroid you could want, somehow failed to produce any volcanism near the impact site, but you are expecting this comparatively small, minor asteroid to produce volcanism (again, for 3 million years)?
3. On page 268 they acknowledge hotspot volcanism in the region. Would it not be more parsimonious to blame flood basalts on the hotspot that they just acknowledged is there?
- "The impact of 17 million years ago was considerably smaller than the one that created the much larger Deccan flood basalt province of India" (238). The Deccan Traps started before the Chicxulub volcano, and even 66 MYA were still on the other side of the planet from Mexico.
- To explain flood basalts in British Columbia: "Perhaps two asteroids struck our region one terrible afternoon 17 million years ago, a big one with a smaller companion" (253). Sure, go ahead, just attribute every geologic question to asteroids. You need 2 asteroids with zero evidence? OK, why not make it 3? Or 10? How many do you want?
This bothers me because not only is the science absurd, but there is no evidence anywhere. As indicated in my quotes above, the authors have no deposits, no geologic evidence, no impact crater. This is all unsubstantiated hearsay, the book version of conspiracy videos on YouTube or the History Channel. It's a 20-page section in a 400 page book, but it really damages the credibility of the authors as scientific guides to anything.
3. The flipside of the focus on every formation is that the authors often fail to see the forest for the trees. There is often little context to the broader historical trends or to what is happening globally, which makes it harder to understand what the geologic formations mean - it is like getting a description of every individual piece of a jigsaw puzzle but never seeing how they fit together. I can demonstrate the issue with 3 maps - the first map of the entire Northwest region appears on page 298; the first map of (most) of North America appears on 328; and the first time-series map showing plate movements appears on page 404 in the epilogue.
October 27, 2016
This is a concise collection of what is known about the geologic history of the northwest portion (WA, OR, CA, ID,MT, NV, WY) of North American. I learned more from this book about the world in which I live than any other book I've ever read. I never took geology in college, but always wished that I had. This book was like taking a course. The chapters are very short and there are a lot of diagrams which helps when describing three dimensional ideas. There is some discussion of types of rock, especially volcanic in origin, but nothing exhaustive.
I admit having been to most of the locations described certainly kept up my interest. I've climbed 750 peaks in the area described in this book, so I have somewhat of a working knowledge of the landscape. A person unfamiliar with the various settings might find the book slightly less fascinating, however there are still a large number of landscape photographs to help identify the key concepts.
In summary, if you live in this part of the world and have an interest in geology, you will like this book. Just get past the introductory chapters about the remotely distant past and then it becomes very engaging. Did you know that the biggest catastrophic floods in the known history of the world happened right here? Did you know that half of Washington State formed when islands from far out in the ocean slowly collided with the main land? Did you know that the Cascade Volcanic Chain is actually the result of water trapped inside the Farallon Plate which is being forced underneath the edge of the continent where it is melted by magma to become super-heated steam? You'll be amazed by all you learn. I now see things in the land which went unnoticed before.
I admit having been to most of the locations described certainly kept up my interest. I've climbed 750 peaks in the area described in this book, so I have somewhat of a working knowledge of the landscape. A person unfamiliar with the various settings might find the book slightly less fascinating, however there are still a large number of landscape photographs to help identify the key concepts.
In summary, if you live in this part of the world and have an interest in geology, you will like this book. Just get past the introductory chapters about the remotely distant past and then it becomes very engaging. Did you know that the biggest catastrophic floods in the known history of the world happened right here? Did you know that half of Washington State formed when islands from far out in the ocean slowly collided with the main land? Did you know that the Cascade Volcanic Chain is actually the result of water trapped inside the Farallon Plate which is being forced underneath the edge of the continent where it is melted by magma to become super-heated steam? You'll be amazed by all you learn. I now see things in the land which went unnoticed before.
September 9, 2009
Fascinating, but if I hadn't been taking an actual college course on this topic there's no way I'd plow through this thing. Geology requires an avid imagination and a sharp analytical mind to even begin to comprehend. This text was not the most easy-to-understand book but considering the subject matter I suppose it is inevitable. Favorite section: probably the one covering the most recent period of time, with all of the repeating ice ages and how they shaped our terrain in the Pacific NW.
June 17, 2016
A clear, detailed, and chronological exhumation of Pacific Northwest Geology. I prefer the beautiful photos and literary prose of Bishop's In Search of Ancient Oregon, but this book provides a look beyond just one state's borders.
I'd be interested in a revised edition that answers some of the controversies and differing interpretations they present.
I'd be interested in a revised edition that answers some of the controversies and differing interpretations they present.
April 2, 2008
Reread November 24, 1999.
This book is worth rereading yet again in few years.
This book is worth rereading yet again in few years.
Displaying 1 - 5 of 5 reviews