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David D. Alt

Autor(a) de Roadside Geology of Oregon

12 Works 1,207 Membros 12 Críticas

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Obras por David D. Alt

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It tells the story of the multiple biblical-scale floods that occurred near the end of the last Ice Age, 10,000+ years ago. The glacier melt-water filled lakes to enormous size and periodically spilled out across Montana, Idaho and Washington States, only to repeat.
 
Assinalado
phoovermt | 1 outra crítica | May 11, 2023 |
We recently went on a geology-heavy trip around Oregon, and this book proved to be a fantastic reference for the most part. The main downsides were that it was a little hard to pinpoint specific areas, as it covered fixed routes, and there were some that weren't addressed. It also was quite dated--there were passages in there that referred to Mount St. Helens without making note of the cataclysmic 1980 eruption! Still, I'd recommend the Roadside Geology series to anyone making similar trips.
 
Assinalado
andorus | Oct 4, 2019 |
At the height of the most recent ice age, from around 17,000 to 10,000 years ago, the northern half of North America was buried beneath a massive ice sheet. Up to three miles thick at its center, the ice sheet sent lobes of glacial ice down into the northern tier of states in the United States. One of these lobes of ice flowed down the Purcell Valley in northern Idaho. As the ice crossed, and eventually blocked the Clark Fork River, it became an ice dam. Behind this dam was formed one of the largest glacial lakes to have existed during the last ice age. Known as Glacial Lake Missoula, it covered an area over 2,900 square miles, and was nearly 2,000 feet deep at its deepest point by the ice dam.

As the lake filled with water, the water was able to eventually float the dam, releasing a catastrophic flood. It is estimated that over 500 cubic miles of water was released emptied from the lake in only a few days time. This flood raced across much of Idaho, Washington, and Oregon through much of the Colombia River basin, creating the spectacular scabland terrain that characterizes eastern Washington.

The flood was amazing, and we can only imagine at what it was like to have seen or experienced this flood. What is even more amazing is that this flood didn’t happen once or twice, but at least thirty-six times! Each successive flood was slightly less massive than the one preceding it, but even the last and smallest flood, was still one of the largest floods to have been recorded.

This amazing lake, and the floods it spawned, is the subject of David Alt's book. Alt is professor of geology at the University of Missoula and has studied Glacial Lake Missoula and its floods since the 1960’s.

Glacial Lake Missoula and its Humongous Floods takes the reader on a journey examining the lake from its source in the valleys of Montana, and down the path of its flood to the coast at the mouth of the Columbia River. The book is well illustrated with photos and maps of Lake Missoula and the scablands that were created by the humongous floods.

Now, I admit that I wasn’t sure what to expect when I began reading this book. I have known about Lake Missoula, and I knew it had catastrophically drained, but not much else. The book's back cover tells the reader that this is “the story of geologists grappling with scientific controversy – ‘of how personalities, pride, and prejudice sometimes supersede scientific evidence.’” This grabbed my attention.

The book is easy to read, I was able to finish it in a few days of reading it during my lunch break. David Alt knows the lake well, and his knowledge is evident as you read the book. Unfortunately, I did not find much coverage devoted to the scientific controversy stated on the back cover. Alt mentions the controversy in the first few chapters, but it is not mentioned again except in passing throughout the rest of the book.

The controversy centers around the work of J Harlen Bretz, a geology professor from the University of Chicago, studied the scablands of Washington and Idaho. He was the first to propose that the scablands were the result of catastrophic floods in 1923. This earned him the derision and scorn of the majority of his colleagues who subscribed to the prevailing thought that there was never a geologic feature that could not be described in terms of slow and careful geologic processes. Catastrophic theory was never to be used as evidence in describing geologic features. Bretz was considered a heretic for many years for this outlandish theory, his critics asking Bretz for the source of all this water. Joseph T. Pardee, a geologist with the US Geological Survey had probably already located the source of Bretz’s flood as he first described Lake Missoula in 1910. It took over 10 years for Pardee to connect Lake Missoula with Bretz’s floods, but soon the evidence was in place.

Unfortunately, this is about the extent of the controversy covered by Alt. The rest of the book covers, in very good detail, the evidence for the lakes existence, and describes the scablands that were created by the floods. The information Alt provides is very detailed, but also reads like a travel log. In places I expected to see mile logs to help me find the locations described by Alt. Actually, mile logs and maps would have been helpful. The book is more appropriate as a travel log. Anyone familiar with the roads through Montana, Idaho, and Washington would be able to find these wonderful locations, but someone unfamiliar with the area would need a good map. The book provides some good maps showing the lake and scablands, but these are not as good for finding the locations.

Overall I found Glacial Lake Missoula and its Humongous Floods to be a good read, but it tried to fluctuate between providing a riveting tale of scientific controversy and a detailed guidebook and travel log for geologic features associated with Lake Missoula. As the former is seems to fall short as Alt spend most of the book describing the glacial lake and the evidence of its flood and very little time is given to the controversy sparked by J Harlen Bretz and other geologists. As the latter, the book is better, but could benefit from actual mile logs and more detailed maps.

Other than diving into the many scientific papers that cover Lake Missoula and its floods, this book is probably the best source for anyone interested in learning more about the lake and the floods.
… (mais)
 
Assinalado
GeoffHabiger | 1 outra crítica | Jun 13, 2018 |
The authors are very keen on the idea that the Yellowstone hot spot was caused by a meteor impact, over which the North American plate has now moved, and which was also responsible for the Columbia flood basalts and the genesis of the Basin and Range province. Hmm. I can almost buy it, particularly given that seismic tomography has shown the Yellowstone hot spot to be unexpectedly shallow, but still.

Kind of a historical thing. The book was published after the recognition of shocked quartz and iridium in the Cretaceous-Paleogene boundary, but before the Chixulub crater in Yucatan was discovered. The authors speculate that the Deccan Traps mark the impact that ended the Cretaceous. Apparently this theory is not quite dead today, though the impact origin of the Shiva feature off the west coast of India is debated. There does seem to be an indication of a cluster of large impacts at about the right time, so it's faintly possible Chixulub was only part of the story.

Otherwise, a pretty good book, with some nice explanation of accretionary wedges from subduction zones. (There are some very old such features in Idaho from when the West Coast was just west of Boise.) Also a bit on mining, which surprised me by not ranting about the irresponsibility of using the cyanide method.
… (mais)
 
Assinalado
K.G.Budge | 2 outras críticas | Aug 8, 2016 |

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Estatísticas

Obras
12
Membros
1,207
Popularidade
#21,277
Avaliação
½ 3.7
Críticas
12
ISBN
13

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