11: Heretics and Heroes
Last week, after six episodes of meteor-riding, magma-diving, and Moonwalking, we met the oldest piece of Earth: a tiny purple zircon crystal from the Jack Hills in Western Australia, 4.4 billion years old. That’s January 14th on our Earth Calendar, the end of the second week. We also learned that this crystal is not alone- there are thousands of slightly younger geezers in the Jack Hills, “only” 4 billion years old.
Until now, we’ve only looked at Earth’s interior- the iron core below and the magma ocean above. But the Jack Hills zircons tell us tales of a new world on the surface, a realm we humans experience every day- the Earth’s crust.
But before we learn how the Hadean crust formed, we need to get familiar with how the modern crust works. Today, we’ll watch how the idea of plate tectonics emerged from controversy into the backbone of modern geology. In the next weeks, we’ll look at ocean and continental crust, and finally start tying all of this knowledge back to the Jack Hills zircons. It might seem like a long detour, but I promise it’s worth it. After these sessions, you’ll know more about the ground beneath your feet, and you’ll have the context to learn about how the crust formed billions of years ago. And it all starts with a story of hardship, prejudice, and redemption.
Part 1: The Jigsaw Puzzle
In 1913, a small Danish expedition crossed the ice cap of northern Greenland. From the beginning, their luck seemed to be cursed when their leader fell into an ice crevasse, taking months to recover. Finally, in summer the team crossed the giant island, taking measurements of the ice and weather. But when they finally reached the western shore, the men found themselves lost. They were only a few miles away from a small town, but they couldn’t find their way through the chaotic glacial terrain. In the words of the German climatologist:
Alfred Wegener on the 1912-13 Greenland Expedition
“I was appalled. After surviving such a long and dangerous journey, and less than two miles from the colony, we were to die here like animals? In July? Was there even a trace of logic to that? Everything inside me rebelled against this thought, and I concentrated all my mental strength on this: I want to live.”
The team ate the last pony, then the last dog. As they were eating their final meal, the men finally saw a boat on the water, and were rescued by a Christian pastor who was sailing through the fjord on his way to confirmation. This harrowing experience did not stop the adventuring spirit of these men, especially the climatologist, who would return to Greenland two more times. His name was Alfred Wegener, and between these expeditions he would launch an idea that would fundamentally change geology forever.
Wegener was born in 1880 in Berlin. He was fascinated by geology and astronomy, but his greatest passions were weather and climate. He used the data from his Greenland expeditions to write textbooks on the atmosphere. With his older brother Kurt, he was one of the first to use weather balloons to collect data, and 1906 they spent 52 hours together in a balloon, a world record at the time.
Wegener also had a fascination with maps, and the more he looked, the more he noticed patterns. Now would be a great time to pull out a world map or globe to follow along. Wegener saw that if you pulled the eastern edge of Brazil to the western edge of Africa they fit together very well. And if you pulled the eastern seaboard of North America down, it would fit against Morocco.
One of Wegener’s maps of Pangaea, illustrating an earlier stage of continental drift. Standard today, revolutionary and reviled in 1924.
This jigsaw puzzle seemed like more than just coincidence, but Wegener knew he needed more evidence. He reasoned that if all the continents were once squeezed together, he would find similar fossils in distant areas. That’s exactly what happened- Wegener found fossils of the same species in Argentina, South Africa, India, Antarctica, and Australia. These were plants and dog-sized reptiles that couldn’t possibly swim across the Atlantic or Indian Oceans. For Wegener, the only explanation for the fossils and the continents’ shapes was that they were once joined together, then drifted apart into the world we know today- so he called this idea continental drift.
Still, Wegener was a climate scientist, not a geologist, and he was not sure if he should make this idea public. The popular idea at the time was that the continents were basically stuck in place, and that creatures used to walk between them on land bridges. Today we know that land bridges can form across narrow waters between Alaska and Siberia. But geologists were proposing bridges crossing the entire Atlantic, bridges that disappeared without a trace.
The land bridge idea was popular, but it did have critics. Wegener saw other scientists literally poke holes in these land bridges, and decided to throw his hat in the ring. It took him ten years to get his idea of continental drift out there- surviving the Greenland expedition and World War I, but eventually his papers were translated in 1922 and Wegener began to speak at international conferences.
Most geologists hated continental drift. To play devil’s advocate for a second, imagine that you’re an established geologist sitting at a major conference. You believe that the continents used to be connected by land bridges. Sure, there were some problems, but serious people were investigating, and there was one good example in Alaska.
Suddenly this German man walks onstage and starts telling you how your land bridges are probably not right at all. There are whispers in the crowd, “Who is this guy? Do you know him? No. I heard he’s just a weatherman. What? Is he at the wrong conference?”
This outsider would then say that continents, entire continents, moved across the face of the Earth, 2 meters every year! And his proof was that some coastlines look similar, with some fossils everyone already knew? Get out of here! Go back to your weather balloons!
And that’s just what Wegener did. He would speak at several meetings, but only a few people took him seriously. He went back to climate research, where he was still respected, and returned to Greenland two more times. In 1930, Alfred Wegener died from heart failure on the Greenland ice cap. He was 50 years old. The next year, his brother Kurt came to bury him in the glacier, 24 years after their wild balloon ride together.
Alfred Wegener’s ideas were still ridiculed when he died. He would have the last laugh, but it would take decades. The best evidence would not come from the continents themselves, but deep beneath the ocean waves.
Part 2: The Cartographer
There was one big problem with Wegener’s idea of continental drift: he couldn’t tell you what made the continents move. He speculated that maybe the Earth’s spin shifted them around like bumper cars, which is not correct. Or perhaps the ocean floor was tearing itself apart, slowly pushing on the surrounding continents.
His ocean hypothesis was absolutely correct, but it was still just speculation. In the 1920s, Wegener had no evidence to prove it.
Across the Atlantic, on a dirt road deep in Alabama, a tall thin man stands beside a truck. It’s a sweltering summer weekend, and he’s wearing a button-down shirt, a tie, and a fedora hat, yet he keeps a steady hand on his surveyor’s tripod. Despite his careful measurements, this man will not prove Wegener’s ideas correct. If we look inside the truck’s flatbed, we see a young girl, no more than 10, making mudpies from the soil her father is studying. Her name is Marie Tharp, and she will become one of the greatest mapmakers of the 20th century.
A young Marie Tharp, soil science assistant, ca. 1930. Image from Lamont-Doherty Earth Observatory, in Landa 2010
Marie Tharp was born in 1920 in Ypsilanti, Michigan. Her father was a soil scientist for the US government, which meant his family was always on the move to measure more dirt. Tharp would join her father on his trips, graduating from mud pies to using a compass and tripod. She was interested in geology as a career, but was told “That was a man’s job”, so her bachelor’s degrees were in English and music. But as she graduated in World War II, many of those men were on the battlefield, and there were suddenly openings for women geologists.
Tharp got a Master’s in petroleum geology and went to the oilfields to find black gold, Texas tea. Except, she wasn’t allowed on the oilrigs- “That was a man’s job”, so she had to stay in the office, sorting through maps. Finally, Tharp grew sick of the oil business and in 1952, she landed a position at Columbia University in New York. Her new job was to make maps of the ocean floor, specifically the North Atlantic. At the time, there were better maps of the Moon’s surface than the ocean floor. So how did she do this, and how does this relate to continental drift? Sonar.
The same sonar technology that hunted submarines in World War II was then used to map the ocean floor. All you had to do was send a sound into the water and wait for the echo to return. The longer the echo took, the deeper the water. If you kept sailing in a straight line, you would be able to read the contours of the ocean like reading Braille.
If you think that Marie Tharp was on these sailing trips, I have five words for you- say them with me now, “That was a man’s job”. Specifically, women at sea were considered bad luck. Sure.
So once again in 1952, Tharp was stuck inside. Her first job was to look at six east to west cruises across the North Atlantic and turn them into undersea maps. What she found was incredible. Scientists knew that there were some mountains at the bottom of the ocean, but Marie discovered that every sonar profile showed a huge mountain chain in the dead center of the Atlantic, going north to south. But there was something even stranger. Each path across this Mid-Atlantic Ridge showed a single giant valley in the middle. When Tharp lined up all of the images together, she correctly deduced that an enormous crack ran down between Europe and North America.
Underwater profiles across the North Atlantic Ocean from west to east, plotted by Marie Tharp in 1952. From Tharpe & Frankel (1986)
Tharp & Heezen investigating their ocean maps.
Her supervisor, a scientist named Bruce Heezen, didn’t believe it. Quote “It cannot be. It looks too much like continental drift.” Other reports say Heezen dismissed the idea as “girl talk”. Twenty-two years after Wegener’s death, his ideas were still scientific poison. In Tharp’s own words, “suggesting that someone believed in continental drift was like saying there was something wrong with them.”
And yet, here was a feature on the ocean floor that Wegener predicted in the 1920s. As the years passed, the evidence grew. Wegener predicted that mid-ocean ridges should be pulling themselves apart, which would produce many undersea earthquakes. When a graduate student lined his earthquake maps on top of Tharpe’s Mid-Atlantic Ridge, the two maps aligned perfectly.
Bruce Heezen was finally convinced this wasn’t “girl talk”, and began to present their findings. Like Wegener, the idea was not well-received at first. The most famous opponent was the legendary French oceanographer Jacques Cousteau. Using the best technology, Cousteau sailed to the Mid-Atlantic and dropped a movie camera attached to a sled on the ocean floor. When he pulled up the sled and saw the film, Jacques Cousteau became a believer. To quote Marie Tharp: “On his film, the great black cliffs of the rift valley… loomed up through the blue-green water. I think that Cousteau’s movies may have convinced a few doubters… that our rift valley was really there.”
The first comprehensive map of the ocean floors by Marie Tharp and Bruce Heezen, 1977
By the 1970’s, Tharp and Heezen produced detailed maps for most of the ocean floor. However, Marie Tharp’s crucial role in discovering the Mid-Atlantic Ridge and others was not well-acknowledged at first. Many of Bruce Heezen’s papers did not include Tharp as a co-author, even though she was the first discoverer. But unlike many other women, Marie would live to see her incredible work acknowledged. She won awards from the National Geographic Society, Columbia University, and the US Library of Congress, where she was named one of the four greatest cartographers of the 20th century.
Summary:
Alfred Wegener and Marie Tharp were both scientists who introduced bold new ideas using data collected from maps. Across an ocean and across generations, they proposed that the oceans are pulling themselves apart, moving continents around Earth’s surface like bumper cars. This idea of plate tectonics is now the fundamental principle of modern geology. I cannot stress this enough. Plate tectonics is behind everything from Mount Everest to the Mariana Trench, from earthquakes to the patterns of life.
Yet, for very different reasons, Wegener and Tharp experienced scorn and dismissal for their ideas. Like many a great artist, Wegener never lived to see himself vindicated. In contrast, Tharp was sable to prove him right, and establish herself as a cornerstone of geology and geography- though many of the issues she faced still plague these fields.
I can’t summarize it any better than Marie Tharp herself. To quote with some mild paraphrase:
“Continental drift and plate tectonics are now accepted theories rather than heresies. The connection between the rift valley(s in the ocean) and the movement of continents has become legitimate. And by the early 1970s, in a complete reversal, the disbelievers were the ones who were thought to have something wrong with them.”
Next episode, we’ll take a walk across one of Marie Tharp’s undersea maps, and learn how crust lives, dies, and transforms into continents.
***
Thank you for listening to Bedrock, a part of Be Giants Media.
If you like what you’ve heard today, please take a second to rate our show wherever you tune in- just a simple click of the stars, no words needed unless you feel like it. If just one person rates the show every week or tells a friend, that makes us more visible to other curious folks. It always makes my day, and that one person could be you. You can drop me a line at bedrock.mailbox@gmail.com. See you next time!
Images:
Wegener in Greenland: https://commons.wikimedia.org/wiki/File:Wegener_1912.gif
Wegener’s Pangaea: https://commons.wikimedia.org/wiki/File:The_origin_of_continents_and_oceans_-_Wegener_(1924)_-_figure_22.jpg
Young Marie Tharp: From the Lamont-Doherty Earth Observatory, in “The Ties that Bind”, Landa (2010).
North Atlantic Profiles: Made by Marie Tharp, From “Mappers of the Deep”, Tharp & Frankel (1986)
Tharp & Heezen: https://www.flickr.com/photos/marietharpmaps/537480113, for use with attribution to website
Ocean Floor Map: https://commons.wikimedia.org/wiki/File:(Manuscript_painting_of_Heezen-Tharp_World_ocean_floor_map_by_Berann).jpg
Music:
Taking it In by Michael Brandon
Wind: https://commons.wikimedia.org/wiki/File:Howling_wind.ogg
The Mastermind by Tiny Music
Crowd: https://commons.wikimedia.org/wiki/File:211146_unfa_another-crowd.flac
Bicycle Bell: https://commons.wikimedia.org/wiki/File:Ding_Dong_Bicycle_Bell_A.ogg
Crickets: https://commons.wikimedia.org/wiki/File:Crickets_choir.ogg
Hebrides Overture, Fingal’s Cave: https://commons.wikimedia.org/wiki/File:Mendelssohn_-_Hebrides_Overture_Fingal%27s_Cave.ogg
Sonar Pings: https://commons.wikimedia.org/wiki/File:Sonar_pings.ogg
Catacombs by Big Score Audio
Movie Projector: https://commons.wikimedia.org/wiki/File:WWS_Super8MovieProjector8211Projection.ogg
Their Arrival by Emmett Cooke
Seven Days of Flying by Remember the Future