The Universe Within: Discovering the Common History of Rocks, Planets, and People

by Neil Shubin

  With this philosophy as a guide, rocks and fossils took on new meaning. About a decade before the aqueduct proposal, Suess became interested in an enigmatic fossil with leaves shaped something like a cow’s tongue. The plant, known as Glossopteris (Latin for “tongue leaves”), was a real mystery. As is typical with larger fossil plants, the whole organism is almost never found; individual leaves, branches, roots, and trunks are used to reconstruct it. This exercise is like putting a three-dimensional puzzle together from incomplete parts. By Suess’s time, Glossopteris was already known to be strange; it had a soft woody interior, making it like a conifer or fern, but it was unlike either in that it carried organs with seeds inside. Judging from the relative sizes of branches and leaves, Glossopteris occasionally rose ninety feet high and may have tapered toward the top, much like a Christmas tree.

  Suess noticed that the really astonishing fact of Glossopteris lay not in its strange leaves but in the rocks that held it. As he followed rock layers with Glossopteris inside, he was able to trace them from South Africa to India all the way to Australia and South America. To Suess, the distribution of Glossopteris meant one thing: these distinct continents were once connected to each other in the distant past. In his thinking, the continents were continuous until the seas rose to separate them.

  Glossopteris figured in both discovery and tragedy. In 1912, Robert Falcon Scott, with four crew members, made a fatal attempt on the South Pole, only to find, upon arrival, that the Norwegian Roald Amundsen had beaten him by several months. Photographs reveal the group’s predicament. They were clearly weakened by the long trek, and their faces in the foreground tell of their fatigue and disappointment while standing against a background of Norwegian tents and flag. Scott’s diary records the difficulties the team experienced pulling heavy sledges on the return trip, how with steadily weakening bodies the weight became too much to bear. Scott, Henry Bowers, and Edward Wilson died in their tent in March 1912, and their bodies were recovered when winter broke eight months later. Lying next to their bodies were thirty-five pounds of rock and fossil. When the samples were brought to the experts at the British Museum, their significance was revealed. The team had discovered Glossopteris at the base of Beardmore Glacier, a hundred miles from the South Pole. Suess didn’t know of this, but it meant that Antarctica too was part of the connections he was envisioning for southern continents.

  The deep meaning of boulders, fossils, and the jigsaw pattern of continents emerged from the mind of an iconoclastic German meteorologist. Alfred Wegener had two major scientific passions in life: understanding the weather over the ice sheets of Greenland and the geography of Earth. He began his career in 1911 serving as a member of some of the earliest scientific explorations of Greenland, including one venture crossing the entire ice cap on foot. His life ended on the island, where on an expedition in 1930 he died on the ice sheet in an effort to rescue some of his crew who were in need of relief.

  Glossopteris, the reconstructed plant and a fossil leaf. (Illustration Credit 6.1)

  Wegener proposed that the different continents were originally connected as one huge supercontinent in the distant past. Over time, the continents drifted apart, forming the configurations of the oceans and coastlines we see today. The first split would have been between a northern chunk and a southern one. This southern one contained what is today Africa, South America, Australia, India, and Antarctica.

  Alfred Wegener in his element. (Illustration Credit 6.2)

  This simple idea answers many questions. Why the special similarity of the plants from the southern continents? Because they were originally part of the same landmass, after the supercontinent broke into chunks. Why glaciers at the equator in India? Because India wasn’t always at the equator; it drifted over time from a position closer to the poles. And why the jigsaw shape of the continents? Because they all fit together at some point millions of years ago.

  What about the response to this grand unifying concept of Wegener’s? Familiar with Glossopteris and the geological similarities among Africa, India, and South America, geologists working in southern continents and Europe tended to view the idea favorably. The reception in North America was something else altogether. The comments of one of my predecessors here at the University of Chicago, in 1920, summarizes the state of affairs: “Wegener’s hypothesis in general is of the footloose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories.”

  Wegener’s critics agreed that the coastlines might have looked like matching jigsaw pieces, but to them the similarity was more coincidence than reality. They could envision no engine that could move the continents. Did the landmasses roar through the ocean crust like icebreakers through pack ice, crunching and crushing miles of rock along the way? Nothing in science spoke to this. In fact, everything we knew of the seafloor at the time spoke to the opposite: the bottom of the ocean appeared to be one of the calmest and most featureless places on Earth.

  Of course, most of the planet was a total mystery in the early part of the twentieth century. Close to 70 percent of Earth is covered by ocean, and in Wegener’s day we knew more of the bright surface of the moon than of Earth.

  GREAT DEPTHS

  December 7, 1941, the day of infamy at Pearl Harbor, had a major impact on our understanding of the planet. Harry Hess, a young geologist at Princeton, was called to war and, being a naval reservist, shipped out from Princeton to New York City to report for active duty on December 8. When he arrived at the headquarters on Church Street, he was asked if he “knew about latitude and longitude.” Little did Hess’s recruiters realize that years before he had been at sea on expeditions to explore and map features of the ocean floor. Hess’s answer to the question was likely satisfactory, as he rose to become navigation and executive officer on the USS Cape Johnson, a maritime freighter converted into a troop transport. The Cape Johnson went to the South Pacific and served during battles at Guam and Iwo Jima. Hess, ever the geologist, had an additional mission in mind during these battles.

  On board the Cape Johnson was a device known as a Fathometer, a simple kind of sonar that measures the depth of the ocean. Modern versions of these devices are small enough to carry on a canoe—think Fishfinder—but during World War II these were the size of a small refrigerator and were towed behind the boat. Hess found a painless way to do science during wartime: just leave the Fathometer running while the Cape Johnson performed its military duties.

  Harry Hess on duty. (Illustration Credit 6.3)

  This effort didn’t cost Uncle Sam much, but it had a large impact on Hess’s thinking. Hess found a number of small flat-topped mountains on the seafloor. These little submarine mesas were to have a major impact on science fifteen years after the war—insights that were kindled when he heard of the work of another person whose life’s trajectory was changed by Pearl Harbor.

  Marie Tharp had no inkling of a career in geology when she matriculated at Ohio University in Athens in the late 1930s. Her path was toward a “proper” woman’s career at the time: nursing or teaching. Nothing clicked. Scared of blood, she left nursing to take courses in education. That curriculum didn’t excite her either. Her opportunity came after the call-up on December 7, when millions of men were pulled from their jobs to fight the Axis powers. The Department of Geology at Michigan broke with long tradition and offered new opportunities for female students to study. The geology scholarship seemed as good a gig as any, so off Tharp went to study Earth.

  By the late 1940s, with her earth science degree in hand, Tharp had gone to New York City to find a job. Her first stop, in the paleontology department at the American Museum of Natural History, was not promising. When she inquired about a position preparing fossils for research and display, her blood ran cold when a paleontologist told her that it took up to two years to discover and remove fossils inside rocks. Tharp later said that she “couldn’t imagine devoting so much time to so
mething like that.” Paleontology’s loss was geology’s gain. Tharp went to Columbia University to meet the head of a major geological team there, Maurice “Doc” Ewing.

  Doc Ewing was a big Texan who was leading an effort to map the seas. In the shift from World War II to the Cold War, one thing remained constant: submariners needed to know about the structure of the ocean floor. The Office of Naval Research filled the demand by funding expeditions worldwide to look at the ocean’s depth and structure. Ewing was sending boats throughout the year to collect cores, depth readings, and other information from the ocean bottoms. With so much data coming in, he required someone to compile and map them. Tharp was hired first; later Ewing recruited an Iowan named Bruce Heezen to direct her and the mapping effort. Heezen swiftly rose through the ranks to become a professor at Columbia, while Tharp remained as his assistant.

  These were heady days in geology. Each month, Doc Ewing’s boats returned with reams of new data from completely unexplored regions of our own world. Tharp and Heezen were in the middle of this frenzy, synthesizing much of the data Ewing’s teams collected. The two worked hard and became very close, but in a way nobody could entirely comprehend. Heezen, a married man, often entertained students and colleagues at Tharp’s house near the laboratory. Some days they would battle, with Heezen throwing Tharp’s drawings in the trash or screaming insults that shattered the normal quiet of the halls. Other times, the two would behave as a team, defending each other during vicious political battles that were part of the environment of the lab. Always close, Tharp and Heezen had a relationship that was, by all accounts, emotionally intense but entirely platonic.

  Bruce Heezen and Marie Tharp. (Illustration Credit 6.4)

  One day, after countless hours compiling shipborne records of the ocean depth, Tharp saw a linear chain of mountains over a mile high that extended along the floor of the Atlantic Ocean. There were solid hints before that these ridges existed, but she followed them as they coursed forty thousand miles on the bottom of the ocean, through virtually every ocean on the globe. Then she looked at the structure of the ridges themselves. Within the apex of each ridge sat what looked like a giant valley—a depression that split the ridge in two. The walls on either side of this valley appeared to match up. Tharp had a hunch what this implied: Earth was opening up at the ridges as it rifted apart at the bottom of the ocean. To her, this was evidence that the seafloor was expanding. Excited, she approached Heezen with the idea.

  Heezen hated Tharp’s discovery, calling it “girl talk.” Like Tharp, he saw the implication immediately. To him, Tharp’s rift in the center of the seafloor looked “too much like continental drift.” If the middles of the oceans were separating, then the continents were moving apart, and Wegener would be right after all. Heezen couldn’t abide this speculation.

  Tharp and Heezen’s map with the giant ridges in the center of the ocean. (Illustration Credit 6.5)

  But Tharp’s data did not go away; in fact, the more she plotted, the more her rift became obvious. Heezen’s resistance withered with the mountain of new data that emerged over the ensuing months. He not only became sold on Tharp’s idea, but he came up with the even more ambitious plan to make a map of the entire ocean floor.

  Around this time, American Telephone and Telegraph realized it had a problem with transatlantic cables that were breaking frequently. The company contracted with Ewing’s lab to check the situation. Plotting the seismic data Ewing’s team collected at a fine scale, Heezen, Tharp, and the team found a stunning pattern. The earthquakes ran in a regular line in the ocean. And not just anywhere in the ocean; they did so in the middle of Tharp’s rift valleys. People started to become very interested in Tharp’s rifts.

  “Girl talk” became the subject of a professional seminar Heezen gave to the assembled experts in the geology department of Princeton University in 1957. In the crowd was Harry Hess, now chairman of the department. After seeing Heezen’s presentation of Tharp’s rifts and their earthquakes inside, Hess rose to say, “Young man, you have shaken the foundations of geology.”

  Hess was primed to love Heezen’s talk because of his work during World War II mapping submarine mountains: they revealed a pattern similar to those of Tharp’s ridges. His mountains were high near the big ridges and became eroded the farther away he looked. To Hess, this meant that the mountains closer to the ridges were relatively young; those farther from the ridges, old. Along with the data revealing active splitting at the ridges, the only explanation could be that new seafloor was created at the ridge and the seafloor was indeed spreading.

  Geological work at this time was an international effort filled with story after story of discovery and persistence. One six-foot-five-inch Dutchman lay curled up in a tiny submarine for weeks on end while mapping deep-sea trenches. British, Canadian, French, Dutch, and Japanese scientists spent months on board ships mapping coasts, oceanic ridges, and trenches. All of this activity brought the need for a new view of Earth. With data pouring in from around the globe, the deep-sea trenches started to reveal a pattern: they too were the sites of frequent earthquakes and, on many occasions, volcanic magma emerging at the surface.

  Heezen’s presentation stimulated Hess to devise a theory to explain the different observations. If new seafloor is created at the ridges, then it had to be recycled somewhere else, lest Earth be ever expanding. To Hess, the pattern of earthquakes and other physical features of the deep trenches fit the bill. He proposed the notion that seafloor emerges at the ridges, spreads as it moves away, and later sinks and is destroyed at the trenches. The seafloor is now seen to be a huge conveyor belt.

  Hess wrote up this idea in a manuscript that he circulated among colleagues but hesitated to publish for two years. He called his idea “an exercise in geopoetry,” as much to defer criticism that it was speculative as to celebrate its beauty. In fact, elements of Hess’s idea, like many ideas in science, had been proposed by somebody else before. Arthur Holmes, a brilliant British geologist, derived a similar recycling idea from pure theory in 1929. Holmes, one of the pioneers in the development of modern methods of dating rocks, found his inspiration in Wegener himself.

  Geopoetry and the recycling of ocean crust.

  Lacking for geopoetry were insights into the age of the seafloor; eroded mountains and rifts alone weren’t going to put an end to almost a century of skepticism. Hess presented his theory at Cambridge in the early 1960s, and in the audience was a young student by the name of Frederick Vine. Excited by Hess’s theory, Vine and his adviser, Drummond Matthews, hunted for an indicator of the age of the rocks at the bottom of the ocean so that they could compare the age of the seafloor on either side of Tharp’s rifts. The two developed a clever technique using the data they had at hand. If the seafloor was spreading like a conveyor belt, then the youngest seafloor should be close to the ridges, and the ages should increase as you move away. Furthermore, the ocean floor should be the same age at the same distance on either side of the ridge. Vine and Matthews used the pattern of magnetism inside the rocks of the seafloor as a marker for their ages. They found exactly what was predicted: young floor is close to the ridge, older floor farther away, and the ages on either side of the ridge match. The seafloor was spreading, just as Hess and Holmes before him had proposed.

  At the same time Vine and Matthews were preparing their publication, Lawrence Morley of the Canadian Geological Survey was assembling his own data. He submitted his analysis to the august journal Nature. It was rejected. He then submitted it to the more specialized Journal of Geophysical Research in 1963. Several months passed. Then it was returned with an anonymous note from one of the referees saying, “Found your note with Morley’s paper on my return from the field. His idea is an interesting one—I suppose—but it seems most appropriate over martinis, say, than in the Journal of Geophysical Research.” This delay cost Morley dearly; soon after he got news of his rejection, Vine and Matthews’s paper appeared.

  Vine and Matthews did not measure the
age of the seafloor directly; the technique they used was so new that it required refinement before Hess’s geopoetry was to become universally accepted. Confirmation came only a few years later with more surveys of the ocean floor led by Columbia, Stanford, and the Scripps Research Institute in La Jolla, California. With the mountains of data, new ideas, and Wegener’s classic insights, Time magazine produced an article in 1970 with a title that says it all: “Geopoetry Becomes Geofact.”

  For professors like Hess and Heezen, this revolution in thinking led to fame and academic eminence. But old feuds die hard. Because of spats with Ewing, largely due to their support of continental drift, Heezen and Tharp had become persona non grata at Columbia. Heezen, a tenured professor, could not be fired, but even so Ewing found ways to demean him: he stripped Heezen of his departmental responsibilities, cored the locks from his office door, dumped his belongings in the hall, and gave his office away. Ewing did manage to fire Tharp. Lacking an office, she ended her career working out of her Nyack, New York, home. Her view of the tumultuous personal and scientific times was revealed twenty years after Heezen’s death when, during an oral history project at Columbia, she recalled, “I worked in the background for most of my career as a scientist, but I have absolutely no resentments. I thought I was lucky to have a job that was so interesting. Establishing the rift valley and the mid-ocean ridge that went all the way around the world for 40,000 miles—that was something important. You could only do that once. You can’t find anything bigger than that, at least on this planet.”