Chapter Content
Okay, so, like, chapter 23... It's all about the moving Earth, you know? And it starts with Einstein, Albert Einstein. Can you believe it? He actually wrote a forward for this book in, like, 1955, which was one of the last things he did, professionally speaking. And the book was called "Earth's Shifting Crust," something like that. Written by this geologist, Charles Hapgood.
Now, Hapgood, he was totally against the idea of continents moving. Like, he actually made fun of people who thought, you know, "Oh, look, South America and Africa fit together!" He, like, said some people, the gullible ones, actually thought the rock structures on both sides of the Atlantic were, get this, the same! Like, exactly the same.
Hapgood just shut that down, completely dismissed it. He said these other geologists, K.E. Caster and J.C. Mendes, had done all this field work and proved those similarities didn’t exist. I mean, who knows where those guys looked because, seriously, rocks *are* the same on both sides. Not just similar, but like, *identical*. I mean, come on.
But, you know, Hapgood, and a lot of geologists back then, they just weren’t buying it.
So, where did this whole continental drift thing come from anyway? This American guy, Frank Bursley Taylor, came up with it back in 1908. He was, like, an amateur geologist. Super rich family, so he could kinda do his own thing without, you know, academic pressure. He noticed, all of a sudden, that Africa and South America looked like they fit together. And he thought maybe the continents just, like, slid around. He even thought – and this was pretty ahead of his time – that mountains formed when continents crashed into each other. But, he didn't have much proof and the theory wasn't taken seriously, to put it mildly.
But, in Germany, this meteorologist, Alfred Wegener, he loved the idea. He was looking at all these weird things about plants and fossils that didn't make sense in the normal history of the earth. Fossils showing up on opposite sides of the ocean, which, obviously, animals can’t swim across. Or how marsupials got from South America to Australia, right? And why the same snails showed up in Scandinavia and New England. And, like, coal deposits and other subtropical leftovers were found in places like Spitsbergen, which is freezing cold. How did that happen?
Wegener figured, maybe all the continents used to be one big piece of land, which he called Pangaea. Then, at some point, that land broke apart and the continents drifted to where they are now. He wrote a book about it in 1912, “The Origin of Continents and Oceans.”
The First World War happened, so it didn't get much attention at first. But in 1920, he put out a revised version, and *then* people started talking.
But, most people thought the continents were only moving *up and down*. This idea, isostasy, of vertical movement was a bedrock belief, even if nobody could actually explain how or why it worked. There was this "prune theory," where the earth was, like, a hot raisin that was cooling and shriveling up, creating oceans and mountains.
But even James Hutton said if the earth were stable, erosion would, like, flatten it. And, Rutherford and Soddy, they figured out that the earth had a ton of internal heat, so there was no cooling and shriveling. Also, mountains weren't all the same age, and they weren't evenly distributed. Time for a new theory. But, geologists were, like, not thrilled about Wegener's.
First off, it was radical, challenged everything they believed. And Wegener was a *meteorologist*! A weatherman! The geologists, they looked for any reason to dismiss him. They invented "land bridges" wherever they needed one to explain the fossil evidence. Fossils of the "three-toed horse" were found in France and Florida, then a land bridge was created. Fossils of ancient tapirs were found in South America and Southeast Asia, another land bridge popped up. Soon, maps were full of these, bridges appeared and vanished as they were needed, transferring species across the globe and then disappearing. It was all totally made up.
But, for half a century, that was the official story. It was orthodoxy.
Some things, land bridges couldn't even explain. There was this trilobite in Europe and Newfoundland, but only on one side of the island. Like, how could it cross all that ocean, but not go around the little corner? Another trilobite was found in Europe and the Pacific Northwest, but nowhere in between! That needed a land bridge, a freakin’ overpass. Seriously. In 1964, the *Encyclopedia Britannica* called Wegener's theory “full of serious theoretical difficulties.”
Wegener wasn’t perfect. He thought Greenland was drifting like a kilometer a year, which was way off, and, he couldn’t explain *how* continents moved. You had to believe that continents were just somehow plowing through solid crust. Nobody knew of any force that could do that.
Arthur Holmes came along. He’s the one who helped figure out how old the earth was. Holmes said that heat in the Earth could cause convection currents, which could slide the continents. He put this in his book, Principles of Physical Geology, in 1944. It was still radical. Americans especially hated the idea. One American was afraid that Holmes' argument was too convincing, and his students would believe it.
But elsewhere, the idea found support. In 1950, the British Association for the Advancement of Science voted that about half their members now accepted continental drift. Hilariously, Hapgood used that as proof of how wrong British geologists were. Holmes himself, he was kinda wishy-washy. He said he never got over an "uneasy distaste" for continental drift, he thought it was "a preposterous assumption."
There was some support for it in America. Reginald Daly defended it, the guy who came up with the idea that the moon was formed by a giant impact. He was seen as interesting, but too out there to take seriously. Most Americans were sticking to their idea that continents had always been where they were.
Interestingly, oil companies had already figured out that they needed to think about plate tectonics to find oil. But, you know, oil geologists don’t write papers. They just find oil.
There was also this big mystery: where did all the sediments go? Rivers bring tons of sediment into the ocean every year. But, if you did the math, the ocean floor should be covered in, like, 20 kilometers of sediment. Scientists just ignored it. For a while.
During World War II, Harry Hess, a mineralogist, was in charge of a ship. It had a fancy new depth finder, and Hess used it for science, even during battle. And he found something amazing. The ocean floor *wasn’t* old and covered in sediment. It was smooth and slick with just a little bit of ancient mud. And it was covered with cliffs and underwater volcanoes. He called them guyots, after this geologist, Arnold Guyot. He had to focus on the war, but he never forgot about it.
After the war, Hess went back to teaching, but the ocean floor stuck with him. In the 50s, oceanographers explored the seabed more. And they found something else amazing: the longest and biggest mountain range on Earth was… underwater. It went all around the planet, like the seams on a tennis ball. It started in Iceland, went down the middle of the Atlantic, around the bottom of Africa, across the Indian and South Pacific oceans, under Australia, across the Pacific, and up the coast of the Americas. Some of the peaks stuck out as islands, like Hawaii, but most of it was kilometers underwater, unknown. It was 75,000 kilometers long!
People didn’t know much about it for a while. Telegraph cable layers had noticed some mountains in the mid-Atlantic, but not the whole thing. And it had this huge, weird crack, like the Earth was splitting open, 20 kilometers wide and 19,000 kilometers long. It was disturbing.
Then, in 1960, rock samples showed that the seabed at the mid-Atlantic ridge was young, and got older as you moved away. Hess realized, the new seabed was forming at the crack, and then being pushed out by newer seabed behind it. The Atlantic was basically two big conveyor belts, pushing the crust towards the continents. They called it seafloor spreading.
When the crust reached the continents, it was forced back into the Earth, subduction. That explained where all the sediment went. And why the seabed was so young, usually less than 175 million years old, while continental rocks were billions of years old. Hess finally understood that the seabed was only as old as the time it took to get to the edge. This was awesome and explained a lot of things. But, it didn’t get much attention.
At the same time, other researchers were looking at something else. In 1906, Bernard Brunhes discovered that the Earth's magnetic field sometimes reversed itself. And that these reversals got recorded in some rocks. Little iron particles in the rocks lined up with the magnetic poles when they formed, and then stayed that way. The rock "remembered" where the poles were. In the 50s, Patrick Blackett and S.K. Runcorn looked at the magnetic patterns in British rocks and, they were shocked to see that the rocks showed that Britain had rotated and moved north. Like it had somehow come untethered! And if you put a map of magnetic patterns in Europe next to one in America, they fit together perfectly, like a torn letter. Weird. Nobody really paid attention.
Then, two guys at Cambridge, Drummond Matthews and Fred Vine, put all the pieces together. Using studies of the magnetic fields of the Atlantic seafloor, they showed that the seafloor was spreading as Hess had said, and the continents were moving. Lawrence Morley, in Canada, came to the same conclusion at the same time, but nobody would publish his paper. The editor of the *Journal of Geophysical Research* told him it was "interesting cocktail-party conversation" but not "serious science." Someone called it “the most significant Earth science paper ever to be rejected.” Ouch.
Finally, the moment for the shifting Earth had come. In 1964, all the big names in the field met in London. All of a sudden, everyone seemed to have changed their minds. Everyone agreed that the Earth was a mosaic of pieces that fit together. And they were all bumping into each other, which explained a lot.
They dropped the name "continental drift" because it wasn’t just the continents that were moving, but the whole crust. It took a while for those fragments to get names. At first they were called "crustal blocks," or "paving stones." In 1968, three American seismologists published a paper in the *Journal of Geophysical Research*, and they got their name: plates. And this new science was called "plate tectonics."
Old ideas die hard. Not everyone bought this new theory. In the 70s, Harold Jeffreys, a well-respected expert, still believed that plate tectonics was physically impossible. He didn't like convection or seafloor spreading either. In 1980, John McPhee pointed out that one in eight American geologists *still* didn’t believe in plate tectonics.
Now, we know that the Earth's surface is made of 8 to 12 big plates. They all move at different speeds and in different directions. Some are big and quiet, some are small and powerful. They don’t necessarily match up with the continents. The North American plate, for instance, is much bigger than the continent. It extends along the west coast, but it doesn’t line up with the east coast at all. It goes halfway across the Atlantic to the mid-Atlantic ridge. Iceland is split in half, half on the American plate, half on the European plate.
It turns out that the relationships between modern and ancient continents are more complicated than we thought. Kazakhstan used to be connected to Norway and New England. Staten Island, just a corner of it, is European. Part of Newfoundland is, too. Pick up a rock on a beach in Massachusetts, and its closest relatives are in Africa. The Scottish Highlands and parts of Scandinavia are partially American. Parts of the Shackleton Mountains in Antarctica may have once been part of the Appalachian Mountains. Rocks get around.
Because of all this constant motion, the plates aren’t going to stay how they are now. If things keep going as they are, the Atlantic will eventually be much bigger than the Pacific. A big part of California will break off and become an island, the Madagascar of the Pacific. Africa will drift north into Europe, push the Mediterranean out of the way, and create a huge Himalayan mountain range between Paris and Calcutta. Austria will connect to islands and be separated from Asia by a narrow strip of land. This is the future. And, also, the present. Things are happening now. While we're sitting here, continents are drifting. Thanks to GPS, we can see that Europe and North America are moving apart at the speed of fingernail growth. If you want to wait long enough, you could drive from Los Angeles to San Francisco. We just don’t live long enough to see it. So, the globe we look at is just a snapshot of continents.
Earth is the only rocky planet with plate tectonics. Why is that? It’s a mystery. It's not just size or density, Venus is like Earth's twin, but it doesn’t have plates. Plates are an important part of how the Earth works. The movement of the tectonic plates affects life on Earth. Challenges caused by tectonics, like climate change, might have pushed forward knowledge. And continental drift may have caused some extinctions. Tony Dickson at Cambridge wrote that the history of rocks and the history of life might be linked. The chemistry of the oceans changes a lot over time. And those changes might be related to events in biological history. Who knows what causes the changes in ocean chemistry. Opening and closing sea ridges might be one.
Plate tectonics explains the dynamics of Earth’s surface, how the three-toed horse got from France to Florida, as well as the planet's inner workings. Earthquakes, island formation, the carbon cycle, the location of mountain ranges, the ice ages, the origin of life, almost everything is influenced by this theory. Geologists were overwhelmed. “The whole Earth suddenly made sense,” McPhee said.
But, only to a degree. The distribution of continents in the past isn’t as well established as most people think. Textbooks are sure about landmasses like Laurasia, Gondwana, Rodinia, and Pangea. But they are based on conclusions that aren’t always accurate. George Gaylord Simpson pointed out that the ancient world was full of plants and animals in places they shouldn’t have been.
Gondwana was a big continent that connected Australia, Africa, Antarctica, and South America. Its boundaries were largely determined by the distribution of fossils of a tongue-shaped plant called Glossopteris. But, Glossopteris was later found in other parts of the world, not connected to Gondwana. This has been largely ignored. Also, fossils of a Triassic reptile called Lystrosaurus have been found from Antarctica to Asia, two places thought to be on the same continent at the time.
And a lot of surface features can’t be explained by tectonics. Take Denver, Colorado. It’s a mile high now, but that’s recent. When dinosaurs roamed the earth, Denver was underwater. But the rocks under Denver aren’t worn or deformed. They should be if Denver was lifted up by colliding plates. And Denver is far from any plate boundaries. Denver seems to have been mysteriously rising for millions of years, like toast.
The same thing is happening in parts of southern Africa. A 1,600 kilometer area has risen about 1.5 kilometers in 10 million years, with no related tectonic activity. Meanwhile, Australia is tilting and sinking. For the last 10 million years, it’s drifted north towards Asia, while its edges have sunk almost 200 meters. Plate theory can’t explain these things.
Alfred Wegener didn’t live to see his theory proven right. In 1930, he set out alone on an expedition to Greenland to check on supplies. He never came back. He was found frozen to death. He’s still buried there, a meter closer to North America than the day he died.
Einstein didn’t live to see that he was wrong, either. He died in Princeton, New Jersey in 1955.
Harry Hess was in Princeton, too, and stayed there for the rest of his life. One of his students, Walter Alvarez, would change science in a totally different way.
As for geology itself, the revolution had just begun. Alvarez would help kick that off, too.