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Crossing The Craton
McPhee embarks on a fascinating journey across the basement of the continent -- the land masses forming Illinois, Iowa, Nebraska, and thereabouts -- with a professor and geochronologist acting as a guide.
300 pages
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About the author
John McPhee
132 books1,860 followersJohn Angus McPhee is an American writer. He is considered one of the pioneers of creative nonfiction. He is a four-time finalist for the Pulitzer Prize in the category General Nonfiction, and he won that award on the fourth occasion in 1999 for Annals of the Former World (a collection of five books, including two of his previous Pulitzer finalists). In 2008, he received the George Polk Career Award for his "indelible mark on American journalism during his nearly half-century career". Since 1974, McPhee has been the Ferris Professor of Journalism at Princeton University.
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October 12, 2020
“Reminders and repetitions can be as useful in this subject as they are in ballads. Rock carries its own epithets, its own refrains. In it, you see things happening again, and now again.”
“If you can do the opposite with deep time, living in it and thinking in it until the large numbers settle into place, you can sense how swiftly the initial earth packed itself together, how swiftly continents have assembled and come apart, how far and rapidly continents travel, how quickly mountains rise and how quickly they disintegrate and disappear.”
“Six hundred feet down is the eastern edge of a great tectonic rift—a rupture of the lithosphere—that reposes there like a sunken boat in the waters of a lake. Filled in during the Precambrian and covered over by sediments of Paleozoic time, the central rift is about thirty miles wide, and trends southwest.
This great rifting of the “stable” craton—basement of the continent—began eleven hundred and eight million years before the present and ended a thousand and eighty-six million years before the present. Continental in scale, it splits North America right up the middle and down one side, threatening to scatter it to who knows what distant corners of the globe.”
I want the book of future geology. Many geologists in the Annals talk about geology repeating itself, and while there are many unknowns, or knowns, like the Rockies being eroded, or beveled down to a level plain and the detritus compressing rock elsewhere; but I want to know where the next Grand Canyon is predicted or the next emergence of a Maroon Bell somewhere. They can predict some rifting areas, and a possible break of continents where oceans may rush in *oh to be there at that moment! And knowing I won’t be is okay, I get the rush thinking of it in present time, in the gift of human imagination and Wendell Berry’s being joyful since it is humanly possible, or the happiness for no reason, just because you can imagine it.*I will hope for this type of thought experiment to come to fruition one day.
“The oldest age of the collected island arcs that are now the primary basement of Colorado is 1790—1.79 billion years. I met Randy Van Schmus a couple of years ago in what he calls “the post-1800-million-year accretionary complex” and most people call Colorado. “Virtually all of Colorado is 1700 to 1790,” Van Schmus said, meaning that the primary crust of Colorado—the collected island arcs—ranges in age from 1700 to 1790 million years. Think of the South Pacific—all that stuff waiting to be accreted. Parts of Fiji are forty million years old and are still waiting to dock. But the Precambrian of Colorado has not been studied extensively enough.”
“Geologists of the next decade will take it apart and tell the story. More advanced techniques will develop. This is the new frontier. To get to new frontiers you go backward in time. The isotopes are telling us this new crust, and about the only way you get new crust is in island arc environments. If you want to see what’s under I-80 in Nebraska, you’re seeing I right here. Nebraska is like this-a few thousand feet down.”
Or. Maybe that isn’t possible to predict since much geologic magic is unique. Take iron for example. “More than ninety per cent of the iron ever mined in the world has come from Precambrian banded-iron formations. The transition that produced them—from a reducing to an oxidizing atmosphere and the associated radical change in the chemistry of the oceans—would be unique. It would never repeat itself. The earth would not go through that experience twice.” About 80% of the Earth's solid inner and liquid outer cores are primarily composed of iron and the electric current generated by the liquid iron creates the magnetic field protecting Earth, according to NASA. Iron is also found in the cores of all of the planets in the Solar System. It is also something the human body needs and is found in many foods. The connection is clear, can you feel a pull for iron of the inner earth? I scoured the internet but could not find how they make the iron supplements for anemia, or even truly where the source is, but it seems like a rock mineral that they need to mine and treat to make the medicine. Also, let me put your mind at ease, we have plenty of banded iron in the world so while perhaps finite, it is plentiful enough no one is worried. On the internet.
“In the Archean world, some think that lithospheric plates, similar in size to the modern plates, moved a good deal faster, with much more volcanism at the plate boundaries and a picture of the earth with its eggshell more shattered, with several times as many plates as exist at the moment—smaller ones, of course, and a vastly greater linear aggregate of plate boundaries, all venting heat.”
Van Schmus continues: “The earth as a whole is producing progressively less heat from radioactive decay, and that, at some point, is going to have a profound effect. In the future, the profound effect is going to be that the plates will stop moving. We’ll be a very static Earth, much like Venus. Isolated hot-spot activity will go on for a while, and then die out. And you’ll basically have a very sedentary Earth. Sometime, it’s going to slow down and stop.”
At one point, the plates were more numerous, and moved faster and there was more drama: volcanoes and probably geysers and earthquakes, and the cooling off the planet from the beginnings is why it has slowed down; and the future brings a stop to the movement. I am not sure they are predicting it yet, but does that mean the end of the Rockies? Some sort of mountain stood in this area for millenia, the Ancestral Rockies, others, all made by a hot spot, a plume that almost rift the North American continent. “Something snuffed it out,” McPhee says, so drily, so North America and the Craton remained intact. Where are the poets to think of what it could have been like if the snuffing didn’t happen? Where are the poets to imagine what did the snuffing as the geologists try to find the why? Or what will earth be like when tectonics stop? McPhee gives a geographical guess: Lincoln, Nebraska and Des Moines, Iowa would be as far as Jersey City and Casablanca, which were truly as close as Lincoln and Des Moines once upon a time, about 190 miles apart. One last comparison for dreams: the rifting under the Craton lasted 22 million years, less than the 40 million years of for the Mid Atlantic Ridge but 3x the length of time the Gulf of California has been widening, and much longer than the Red Sea at 5 million years.
“The Arkansas River runs fast and white most of the way, maybe a hundred feet wide. The rock around it towers. As the river approaches its debouchment into the flats of eastern Colorado, it makes one last slice that by an order of magnitude is the deepest of all. Like a knife disappearing into a large loaf of bread, it has cut an extremely narrow gorge whose rims are more than a thousand feet above the rapids called the Royal Gorge.” I only visited The Royal Gorge once, with my mom, on a winter’s day that had no light, and was underwhelmed by the bridges and the machinery and human detritus all around. Now there is zip line. See digression below.
More quotes:
“His own lifetime—beginning in the calendar year 1938 and expecting at least four score and ten—was a submicroscopic speck at the end of a widening shaft of information and thought that could reach to and bracket those four hundred million years. The difference between one human lifetime and four hundred million years would seem to be a difference between time incomprehensible and time infinitesimal, but what brings them together is that the smaller unit—bridging in the mind the intervening eons—can imagine and virtually see the larger one.”
“Rifts meeting at a triple junction are a signature of plate tectonics and can be seen all over the modern world—in the far-south Atlantic, where the African, Antarctic, and South American plates conjoin; in the Azores, where the African, Eurasian, and North American plates conjoin; in the Indian Ocean; at the Galapagos Islands; at Cape Mendocino in California.
To sense most clearly, though, the Precambrian rift system that lies under the middle of North America, look at a map of African an Arabia. The Red Sea, the Gulf of Aden, and the East African Rift Valley meet in a triple junction for about 20 million years.”
“The oldest rock ever found on earth is actually 3.96 billion years. The oldest rock in the United States is in the Minnesota River Valley—about 3.5 billion years. There is rock in West Greenland that is 3.8, in Australia about 3.5. Some rocks in Africa are as old as 3.6 but it is interesting that the oldest known rock comes from North America at Great Bear Lake, in the Canadian Northwest Territories, almost exactly on the Arctic Circle and it is deformed foliated gneiss as basement rock from the Wopmay Orogeny, and they know from zircons in sandstones in Australia that there were igneous rocks crystallizing 4.2 billion years ago. So there were older rocks, but they’ve either been destroyed or not found yet.”
“From an interstellar gas cloud, evidently, the solar system began to form about 4.56 billion years ago. Gravity, a shock wave from a supernova—or something—caused the gas cloud to collapse, becoming incandescent vapor, in which minerals formed dust that included cometary material that had water in it.
Meteors kept on showering, accreting, increasing the size of the earth. Around 3.9 billion years before the present, meteor impacts were particularly intense.”
“About 1850 (1.85 billion years before the present), the Wyoming, Hearne, and Superior microcontinents came together, and the belt of deformation that held them tight is known in the science as the Trans-Hudson Orogen. A closed ocean, it is full of the crunched remains of oceanic islands. In 1900, they might have looked much like Indonesia today, but without its vegetation. By 1830, they would have resembled what Indonesia will look like after it collides with Asia. By 1800, over-all, the Canadian Shield was complete. From 1800 to 1400, most of North America grew on its margins.
Stiff and strong it surely is. Like few erosional surfaces in the world, it has been sitting pat for
sixteen hundred million years with nothing serious happening.”
“Their docking times—the dates when they connected with the Wyoming craton and with one another—are a good deal more difficult to determine, but on the average the islands seem to have existed in the ocean for ten to twenty million years before they collided with something else.”
A digression https://royalgorgeregion.com/ (I feel like McPhee would have put this in, but he admits the Craton, that giant area of hidden, flat, unromantic rock from Ohio to the Rockies, haunted him and he had to quickly write about it.) ( I also lost a little steam and will need to revisit this one day.)
The 1,469-mile long Arkansas River is the second longest tributary of the Mississippi River, the sixth longest river in the US, and the most distinctive feature in Fremont County, Colorado. Tucked in a canyon on Mt. Arkansas, the East Fork of the Arkansas River rises to an elevation of 12,525’ south of Fremont Pass, after which it is joined by Tennessee Creek at 9,800’ between Leadville and Turquoise Lake. The river then drops 4,650’ over 152 miles and levels out considerably by the time it leaves the Royal Gorge on the way to Lake Pueblo. After flowing 360 miles through Colorado, the river leaves the state at 3,350’.
At its headwaters, the Arkansas River is a wild mountain stream flowing south, then southeasterly. The river drains over 25,000 square miles of Colorado, the largest drainage area in the state. Since 1908, its flows have been augmented by trans-mountain diversions of water from Colorado’s Western Slope, tunneled under the Continental Divide. Today there are 9 such diversions accounting for 69,500 acre-feet annually.
The river flows between the 14,000’ Collegiate Peaks of the Sawatch Range that forms the Continental Divide on the west and the somewhat lower Mosquito Range to the east. The valley floor is 3 to 10 miles wide and about 5,000’ to 7,000’ below the mountain peaks. This is not a typical river valley caused by erosion. Rather, this is the northern portion of the Rio Grande Rift, a crack in the earth’s crust caused by tectonic forces that created an upwelling of Earth’s mantle during the mid-Tertiary period about 20 million years ago, separating the Colorado Plateau of Colorado, Arizona, Utah and New Mexico from the Great Plains. The Graben, as it is called, has four segments, including the Upper Arkansas and San Luis Valley that run from southern Wyoming deep into Mexico.
According to one school of geologic thought, the Arkansas River once flowed south and was part of the Rio Grande River. Poncha Pass is thought to have risen from uplift and volcanic activity, forcing the river to turn east some 2 to 5 million years ago where it found find its way through the uplifted Horst of the rift, other faults, the complex geology of the Big Horn Sheep Canyon, Pleasant Valley, and the Royal Gorge. Another school of geologic thought claims the Arkansas River has always followed its present course.
Glaciers add an additional element to the story of the Arkansas River. Less than 1 million years ago, three glaciers formed a 670’-high ice dam near what is now Granite, Colorado. It blocked the upper Arkansas River and created a large lake at least 500’ deep that extended 14 miles north toward Leadville. When the ice dam broke, catastrophic glacial floods deposited a sheet of boulders as much as 60’ thick 10 miles down the river, leaving two residual river terraces at levels 20’ and 50’ above the river. The flood waters were deep enough to leave 4’ boulders as much as 160’ up the canyon wall. Two such floods are thought to have occurred, 10,000 to 16,000 years ago.
The River that flows through the 10-mile long Royal Gorge is comprised of Precambrian gneiss, schist, granite, and other material at a depth of about 1,200’. The Royal Gorge is a deep, geologically young, and unusually narrow canyon. At places, it’s only 30’ wide. The gorge is the product of three periods of uplift, the most recent about 1 million years ago, when geologic faulting or fracturing created a crack in the earth’s crust, while the river continued grinding away at its bed.
After breaking out of the Rocky Mountains above Cañon City, the gradient of the river changes from an average drop of 40’ per mile to a much gentler fall of less than 9’ per mile as it enters the Colorado Piedmont region of the Great Plains. Here, the river is no longer a rushing mountain stream but rather the meandering river that will characterize the rest of its flow to the Missississipi River.
“If you can do the opposite with deep time, living in it and thinking in it until the large numbers settle into place, you can sense how swiftly the initial earth packed itself together, how swiftly continents have assembled and come apart, how far and rapidly continents travel, how quickly mountains rise and how quickly they disintegrate and disappear.”
“Six hundred feet down is the eastern edge of a great tectonic rift—a rupture of the lithosphere—that reposes there like a sunken boat in the waters of a lake. Filled in during the Precambrian and covered over by sediments of Paleozoic time, the central rift is about thirty miles wide, and trends southwest.
This great rifting of the “stable” craton—basement of the continent—began eleven hundred and eight million years before the present and ended a thousand and eighty-six million years before the present. Continental in scale, it splits North America right up the middle and down one side, threatening to scatter it to who knows what distant corners of the globe.”
I want the book of future geology. Many geologists in the Annals talk about geology repeating itself, and while there are many unknowns, or knowns, like the Rockies being eroded, or beveled down to a level plain and the detritus compressing rock elsewhere; but I want to know where the next Grand Canyon is predicted or the next emergence of a Maroon Bell somewhere. They can predict some rifting areas, and a possible break of continents where oceans may rush in *oh to be there at that moment! And knowing I won’t be is okay, I get the rush thinking of it in present time, in the gift of human imagination and Wendell Berry’s being joyful since it is humanly possible, or the happiness for no reason, just because you can imagine it.*I will hope for this type of thought experiment to come to fruition one day.
“The oldest age of the collected island arcs that are now the primary basement of Colorado is 1790—1.79 billion years. I met Randy Van Schmus a couple of years ago in what he calls “the post-1800-million-year accretionary complex” and most people call Colorado. “Virtually all of Colorado is 1700 to 1790,” Van Schmus said, meaning that the primary crust of Colorado—the collected island arcs—ranges in age from 1700 to 1790 million years. Think of the South Pacific—all that stuff waiting to be accreted. Parts of Fiji are forty million years old and are still waiting to dock. But the Precambrian of Colorado has not been studied extensively enough.”
“Geologists of the next decade will take it apart and tell the story. More advanced techniques will develop. This is the new frontier. To get to new frontiers you go backward in time. The isotopes are telling us this new crust, and about the only way you get new crust is in island arc environments. If you want to see what’s under I-80 in Nebraska, you’re seeing I right here. Nebraska is like this-a few thousand feet down.”
Or. Maybe that isn’t possible to predict since much geologic magic is unique. Take iron for example. “More than ninety per cent of the iron ever mined in the world has come from Precambrian banded-iron formations. The transition that produced them—from a reducing to an oxidizing atmosphere and the associated radical change in the chemistry of the oceans—would be unique. It would never repeat itself. The earth would not go through that experience twice.” About 80% of the Earth's solid inner and liquid outer cores are primarily composed of iron and the electric current generated by the liquid iron creates the magnetic field protecting Earth, according to NASA. Iron is also found in the cores of all of the planets in the Solar System. It is also something the human body needs and is found in many foods. The connection is clear, can you feel a pull for iron of the inner earth? I scoured the internet but could not find how they make the iron supplements for anemia, or even truly where the source is, but it seems like a rock mineral that they need to mine and treat to make the medicine. Also, let me put your mind at ease, we have plenty of banded iron in the world so while perhaps finite, it is plentiful enough no one is worried. On the internet.
“In the Archean world, some think that lithospheric plates, similar in size to the modern plates, moved a good deal faster, with much more volcanism at the plate boundaries and a picture of the earth with its eggshell more shattered, with several times as many plates as exist at the moment—smaller ones, of course, and a vastly greater linear aggregate of plate boundaries, all venting heat.”
Van Schmus continues: “The earth as a whole is producing progressively less heat from radioactive decay, and that, at some point, is going to have a profound effect. In the future, the profound effect is going to be that the plates will stop moving. We’ll be a very static Earth, much like Venus. Isolated hot-spot activity will go on for a while, and then die out. And you’ll basically have a very sedentary Earth. Sometime, it’s going to slow down and stop.”
At one point, the plates were more numerous, and moved faster and there was more drama: volcanoes and probably geysers and earthquakes, and the cooling off the planet from the beginnings is why it has slowed down; and the future brings a stop to the movement. I am not sure they are predicting it yet, but does that mean the end of the Rockies? Some sort of mountain stood in this area for millenia, the Ancestral Rockies, others, all made by a hot spot, a plume that almost rift the North American continent. “Something snuffed it out,” McPhee says, so drily, so North America and the Craton remained intact. Where are the poets to think of what it could have been like if the snuffing didn’t happen? Where are the poets to imagine what did the snuffing as the geologists try to find the why? Or what will earth be like when tectonics stop? McPhee gives a geographical guess: Lincoln, Nebraska and Des Moines, Iowa would be as far as Jersey City and Casablanca, which were truly as close as Lincoln and Des Moines once upon a time, about 190 miles apart. One last comparison for dreams: the rifting under the Craton lasted 22 million years, less than the 40 million years of for the Mid Atlantic Ridge but 3x the length of time the Gulf of California has been widening, and much longer than the Red Sea at 5 million years.
“The Arkansas River runs fast and white most of the way, maybe a hundred feet wide. The rock around it towers. As the river approaches its debouchment into the flats of eastern Colorado, it makes one last slice that by an order of magnitude is the deepest of all. Like a knife disappearing into a large loaf of bread, it has cut an extremely narrow gorge whose rims are more than a thousand feet above the rapids called the Royal Gorge.” I only visited The Royal Gorge once, with my mom, on a winter’s day that had no light, and was underwhelmed by the bridges and the machinery and human detritus all around. Now there is zip line. See digression below.
More quotes:
“His own lifetime—beginning in the calendar year 1938 and expecting at least four score and ten—was a submicroscopic speck at the end of a widening shaft of information and thought that could reach to and bracket those four hundred million years. The difference between one human lifetime and four hundred million years would seem to be a difference between time incomprehensible and time infinitesimal, but what brings them together is that the smaller unit—bridging in the mind the intervening eons—can imagine and virtually see the larger one.”
“Rifts meeting at a triple junction are a signature of plate tectonics and can be seen all over the modern world—in the far-south Atlantic, where the African, Antarctic, and South American plates conjoin; in the Azores, where the African, Eurasian, and North American plates conjoin; in the Indian Ocean; at the Galapagos Islands; at Cape Mendocino in California.
To sense most clearly, though, the Precambrian rift system that lies under the middle of North America, look at a map of African an Arabia. The Red Sea, the Gulf of Aden, and the East African Rift Valley meet in a triple junction for about 20 million years.”
“The oldest rock ever found on earth is actually 3.96 billion years. The oldest rock in the United States is in the Minnesota River Valley—about 3.5 billion years. There is rock in West Greenland that is 3.8, in Australia about 3.5. Some rocks in Africa are as old as 3.6 but it is interesting that the oldest known rock comes from North America at Great Bear Lake, in the Canadian Northwest Territories, almost exactly on the Arctic Circle and it is deformed foliated gneiss as basement rock from the Wopmay Orogeny, and they know from zircons in sandstones in Australia that there were igneous rocks crystallizing 4.2 billion years ago. So there were older rocks, but they’ve either been destroyed or not found yet.”
“From an interstellar gas cloud, evidently, the solar system began to form about 4.56 billion years ago. Gravity, a shock wave from a supernova—or something—caused the gas cloud to collapse, becoming incandescent vapor, in which minerals formed dust that included cometary material that had water in it.
Meteors kept on showering, accreting, increasing the size of the earth. Around 3.9 billion years before the present, meteor impacts were particularly intense.”
“About 1850 (1.85 billion years before the present), the Wyoming, Hearne, and Superior microcontinents came together, and the belt of deformation that held them tight is known in the science as the Trans-Hudson Orogen. A closed ocean, it is full of the crunched remains of oceanic islands. In 1900, they might have looked much like Indonesia today, but without its vegetation. By 1830, they would have resembled what Indonesia will look like after it collides with Asia. By 1800, over-all, the Canadian Shield was complete. From 1800 to 1400, most of North America grew on its margins.
Stiff and strong it surely is. Like few erosional surfaces in the world, it has been sitting pat for
sixteen hundred million years with nothing serious happening.”
“Their docking times—the dates when they connected with the Wyoming craton and with one another—are a good deal more difficult to determine, but on the average the islands seem to have existed in the ocean for ten to twenty million years before they collided with something else.”
A digression https://royalgorgeregion.com/ (I feel like McPhee would have put this in, but he admits the Craton, that giant area of hidden, flat, unromantic rock from Ohio to the Rockies, haunted him and he had to quickly write about it.) ( I also lost a little steam and will need to revisit this one day.)
The 1,469-mile long Arkansas River is the second longest tributary of the Mississippi River, the sixth longest river in the US, and the most distinctive feature in Fremont County, Colorado. Tucked in a canyon on Mt. Arkansas, the East Fork of the Arkansas River rises to an elevation of 12,525’ south of Fremont Pass, after which it is joined by Tennessee Creek at 9,800’ between Leadville and Turquoise Lake. The river then drops 4,650’ over 152 miles and levels out considerably by the time it leaves the Royal Gorge on the way to Lake Pueblo. After flowing 360 miles through Colorado, the river leaves the state at 3,350’.
At its headwaters, the Arkansas River is a wild mountain stream flowing south, then southeasterly. The river drains over 25,000 square miles of Colorado, the largest drainage area in the state. Since 1908, its flows have been augmented by trans-mountain diversions of water from Colorado’s Western Slope, tunneled under the Continental Divide. Today there are 9 such diversions accounting for 69,500 acre-feet annually.
The river flows between the 14,000’ Collegiate Peaks of the Sawatch Range that forms the Continental Divide on the west and the somewhat lower Mosquito Range to the east. The valley floor is 3 to 10 miles wide and about 5,000’ to 7,000’ below the mountain peaks. This is not a typical river valley caused by erosion. Rather, this is the northern portion of the Rio Grande Rift, a crack in the earth’s crust caused by tectonic forces that created an upwelling of Earth’s mantle during the mid-Tertiary period about 20 million years ago, separating the Colorado Plateau of Colorado, Arizona, Utah and New Mexico from the Great Plains. The Graben, as it is called, has four segments, including the Upper Arkansas and San Luis Valley that run from southern Wyoming deep into Mexico.
According to one school of geologic thought, the Arkansas River once flowed south and was part of the Rio Grande River. Poncha Pass is thought to have risen from uplift and volcanic activity, forcing the river to turn east some 2 to 5 million years ago where it found find its way through the uplifted Horst of the rift, other faults, the complex geology of the Big Horn Sheep Canyon, Pleasant Valley, and the Royal Gorge. Another school of geologic thought claims the Arkansas River has always followed its present course.
Glaciers add an additional element to the story of the Arkansas River. Less than 1 million years ago, three glaciers formed a 670’-high ice dam near what is now Granite, Colorado. It blocked the upper Arkansas River and created a large lake at least 500’ deep that extended 14 miles north toward Leadville. When the ice dam broke, catastrophic glacial floods deposited a sheet of boulders as much as 60’ thick 10 miles down the river, leaving two residual river terraces at levels 20’ and 50’ above the river. The flood waters were deep enough to leave 4’ boulders as much as 160’ up the canyon wall. Two such floods are thought to have occurred, 10,000 to 16,000 years ago.
The River that flows through the 10-mile long Royal Gorge is comprised of Precambrian gneiss, schist, granite, and other material at a depth of about 1,200’. The Royal Gorge is a deep, geologically young, and unusually narrow canyon. At places, it’s only 30’ wide. The gorge is the product of three periods of uplift, the most recent about 1 million years ago, when geologic faulting or fracturing created a crack in the earth’s crust, while the river continued grinding away at its bed.
After breaking out of the Rocky Mountains above Cañon City, the gradient of the river changes from an average drop of 40’ per mile to a much gentler fall of less than 9’ per mile as it enters the Colorado Piedmont region of the Great Plains. Here, the river is no longer a rushing mountain stream but rather the meandering river that will characterize the rest of its flow to the Missississipi River.
August 30, 2024
This is not much more than an essay at the end of Annals of the Former World, so it’s hard to argue that I’m not just padding my stats. But as with everything John McPhee writes, it��s worth it’s weight in gold. And he talks about Iowa City limestone, so 🤷🏼
December 19, 2011
Typical John Mcfee in that I understood about half of the geology but the book was so well written that it didn't bother me much.
February 1, 2020
His thesis: North America’s northern Great Plains / Great Lakes are really really old. So old down at the bottom that they predate fossils, and so aren’t that geologically interesting— or, maybe they are. There are still hidden plates to unearth, stories of tectonic movement that could have split the continent but cooled down and didn’t, and geologists doing dating from zircon to understand just how old is old.
May 9, 2023
I have read this book about 4 times. Its the last in a series McPhee wrote about traversing segments North America with different geologists to understand how the continent formed. This sounds about as interesting as sawdust, but in reality it's fascinating. "The Craton" is the stable interior of the continent - essentially the flat spot between the Appalachian Mountains and the Rocky Mountains. There is far more to this settled bit of landscape than meets the eye. Much of the story of the Craton is from the Precambrian - over 540 million years ago. This is a time that pre-dates nearly all fossils. It predates life in general and has traditionally been ignored by most geologists. yet the Precambrian makes up the bulk of Earths history. The planet is about 4.5 billion years old and our geologic time scale - at least the portion most people are familiar with, only covers from 0.542 of the 4.5 billion years the planet has existed. Rather than fossils as waypoints, the Precambrian is navigated using isotopes - its all radiometric dating.
As a non-geologist, McPhee is the perfect person to write about this topic as he can actually translate it into terms non-geologists can understand. I would not call the book exciting, but for anyone interested in the early history of the earth and those who study it, its a gratifying book to read.
Note the book is presented both in a compendium entitled "Annals of the Former World" (Pictured above) with the other books in the series - and its also sold as a separate volume as are all the other books in the series.
As a non-geologist, McPhee is the perfect person to write about this topic as he can actually translate it into terms non-geologists can understand. I would not call the book exciting, but for anyone interested in the early history of the earth and those who study it, its a gratifying book to read.
Note the book is presented both in a compendium entitled "Annals of the Former World" (Pictured above) with the other books in the series - and its also sold as a separate volume as are all the other books in the series.
January 10, 2025
Serving as a coda to the proper books in the Annals of the Former World series, Crossing The Craton tells the tale of the flat-on-the-surface middle part of the current North American continent. As always, McPhee bombards the reader with massive lists of geologic terms those short of degrees in the area will find mind numbing. This volume lacks an interesting "protagonist" in the form of a geologist McPhee accompanies out in the field. Instead, an education on 1980's cutting edge rock dating technologies is in order. It was interesting to learn there are massive rifts miles below the boring surface of the Midwest. That aside, I was middled by this effort and will likely not return to McPhee now that I'm done reading his Annals.
June 25, 2022
The version of this book that I read was that of a short chapter of the larger work, a bound copy of Annals of the Former World, 660 pages long. Perhaps some of this geology stuff is sinking in, or perhaps this was one of the easier books, or perhaps the author's prose has gotten better. But I found this short book to be more understandable. Perhaps because it seems to be a newer branch of geology in that it is about older rocks that were harder to study until more recently? A comparatively pleasant read - though still hard to follow.
January 15, 2025
This is the final volume of Annals of a Former World. Coincidentally I just read a short piece in the New Yorker by John McPhee. He is publishing short scraps of writing that have not been published before. He calls these pieces Tabula Rasa. One piece is about a swimming pool he had installed near his house. Now it has fallen into disrepair and is not longer used.
October 3, 2022
Crossing the Craton was added after the first four parts were completed to correct and ommission, the midwest. Crossing the Craton. It tells the story of America's deep rock basement, which underlies the waves of grain. I really need to read the other 4 books
January 14, 2025
More of a concluding chapter than a final book, but since one question that I kept idly thinking about through the rest of the series was, what do we know about the really old rocks, when the Earth was quite young? I found it quite satisfying.
October 13, 2022
4.5. Solid finish to the epic “annals of the former world.
February 4, 2025
I listened to this book, and always miss details when I don’t read a work.
May 10, 2025
Loved it will reread.
Made driving the 80 across Nebraska and Iowa quite fascinating. Food for daydreaming about what’s underneath everything
Made driving the 80 across Nebraska and Iowa quite fascinating. Food for daydreaming about what’s underneath everything
October 30, 2025
Last of in the series of John McPhee’s geology books. Highly recommend all of these. He’s so great at teaching us regular people this info.
November 9, 2025
Look into the deep past. Methodologies interesting.
Read
February 23, 2016You might think that the vast flattish middle of the North American continent is the least interesting part geologically, but it turns out to be surprisingly misterioso and even rather poetic because much of it dates from a period that is relatively inaccessible to science even now. I had always sort of assumed that older rock basically lay under younger rock all the way down, but that turns out to be incorrect!
McPhee wrote this piece, which is more like a long essay than a short book, explicitly to cover the big gaping lacuna in his masterpiece about the American continent but it has a "day late and dollar short" feel to it. There's a distinct lack of the colorful personalities, awesome landscapes, and outdoor adventures that mark his best work... more dry accountings of what scientists in labs have discovered through various types of probes and a lot of computer programming. I'm sure that this is a good reflection of how the science of geology itself has changed but it's a dispiriting read with a quite abrupt ending that feels cut off rather than wrapped up. Most people will read this only after the many thousands of words that make up what is now known as _Annals of the Former World_, and that's definitely the best audience for it: geological completionists.
McPhee wrote this piece, which is more like a long essay than a short book, explicitly to cover the big gaping lacuna in his masterpiece about the American continent but it has a "day late and dollar short" feel to it. There's a distinct lack of the colorful personalities, awesome landscapes, and outdoor adventures that mark his best work... more dry accountings of what scientists in labs have discovered through various types of probes and a lot of computer programming. I'm sure that this is a good reflection of how the science of geology itself has changed but it's a dispiriting read with a quite abrupt ending that feels cut off rather than wrapped up. Most people will read this only after the many thousands of words that make up what is now known as _Annals of the Former World_, and that's definitely the best audience for it: geological completionists.
May 21, 2025
McPhee uses a conversational approach to tackle the broad topic of geology. This is just one book of the Pulitzer-winning tome, Annals of the Former World. McPhee, a pioneer of creative nonfiction, uses personal anecdote to describe some of the issues in geology: field work vs computer modeling; the use/misuse of continental drift theory; government vs academic vs for-profit geological work. McPhee’s wryly humorous tone and focus on certain personalities makes this book more engaging than I expected.
August 9, 2025
I love John McPhee's fascinating and extraordinarily accessible books about geology. In my next life, when I major in Earth Science rather than English and German, I will own them all. For now, I can simply enjoy the wealth of detail he presents and the fascinating landscapes he describes. Too bad they aren't all available on cd. I'm afraid these will be lost in the shuffle as we librarians convert totally to cd. A shame, really.
December 18, 2013
See my complete review here:
http://whatmeread.wordpress.com/tag/c...
http://whatmeread.wordpress.com/tag/c...
July 4, 2015
Really enjoyable, though short. I loved the talk about dates like 1850 and 1729, when what was meant was 1850 and 1729 million years ago. Deep time.
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