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A review by left_coast_justin
In Suspect Terrain by John McPhee
5.0
Think about diamonds for a minute. So far as we know, there are only two places these occur in nature. One is in very widely-scattered sites on Earth, and the others are little microdiamonds that are sometimes found on meteors.
I think we all realize that enormous heat and pressure are required to form a diamond. So the inside of a volcano might be a good place, right? Uhhh, no. Not nearly enough pressure. Volcanoes are essentially weak points in the Earth's crust where lava can bubble out. No, to form a diamond, you need to go towards the middle of a tectonic plate, the most stable places on Earth, and go down. Way down. Sixty or seventy miles down. The center of the tectonic plates are the only places where the crust is this thick. Any carbon that finds its way down there will be converted to diamond.
Then the problem becomes getting it to the surface. How do diamonds move sixty miles upwards through solid, stable rock? And that's not all: If the diamonds were to migrate upwards at slow to moderate speeds into regions of lower pressure and lower temperature before reaching the surface, they would quickly revert to graphite, which is the most stable form of pure carbon. (Diamonds are emphatically not forever.) So they have to emerge from down there at high speed. In fact, they have to be blown out of the ground at twice the speed of sound in order to survive the trip, where they 'freeze' in their distinctive crystal structure. For reasons that nobody quite understands, every so often a 'diamond pipe' explodes out of the surface of the most stable regions of the earth. This has never happened in human history, but, as McPhee notes, one could pop up under Kansas City next week.
I strongly recommend reading this book. It's just full of stuff like this. So many fun things to learn!
(Nov. 17, 2020)
I'm so happy to be re-reading these books! One wonderful page after another.
I think we all realize that enormous heat and pressure are required to form a diamond. So the inside of a volcano might be a good place, right? Uhhh, no. Not nearly enough pressure. Volcanoes are essentially weak points in the Earth's crust where lava can bubble out. No, to form a diamond, you need to go towards the middle of a tectonic plate, the most stable places on Earth, and go down. Way down. Sixty or seventy miles down. The center of the tectonic plates are the only places where the crust is this thick. Any carbon that finds its way down there will be converted to diamond.
Then the problem becomes getting it to the surface. How do diamonds move sixty miles upwards through solid, stable rock? And that's not all: If the diamonds were to migrate upwards at slow to moderate speeds into regions of lower pressure and lower temperature before reaching the surface, they would quickly revert to graphite, which is the most stable form of pure carbon. (Diamonds are emphatically not forever.) So they have to emerge from down there at high speed. In fact, they have to be blown out of the ground at twice the speed of sound in order to survive the trip, where they 'freeze' in their distinctive crystal structure. For reasons that nobody quite understands, every so often a 'diamond pipe' explodes out of the surface of the most stable regions of the earth. This has never happened in human history, but, as McPhee notes, one could pop up under Kansas City next week.
I strongly recommend reading this book. It's just full of stuff like this. So many fun things to learn!
(Nov. 17, 2020)
If geologic time could somehow be seen in the perspective of human time, on the other hand, sea level would be rising and falling hundreds of feet, ice would come pouring over continents and as quickly go way. Yucatans and Floridas would be under the sun one moment and underwater the next, oceans would swing open like doors, mountains would grow like clouds and come down like melting sherbet, continents would crawl like amoebae, rivers would arrive and disappear like rainstreaks on an umbrella, lakes would go away like puddles after a rain, and volcanoes would light the earth as if it were a garden full of fireflies. At the end of the program, man shows up -- his ticket in his hand. Almost at once, he conceives of private property, dimension stone, and life insurance. When a Mt. St. Helens assaults his sensibilities with an ash cloud eleven miles high, he writes a letter to the New York Times recommending that the mountain be bombed.
I'm so happy to be re-reading these books! One wonderful page after another.