THE GEOLOGY METHODOLOGY: THE CRACKS THAT LEAD TO CIVILIZATION

In “The Geology Methodology,” Season 11, Episode 7, Sheldon shows his misplaced dislike for geology.

“Earth scientists had just discovered something fascinating about the continent [she] was standing on, incidentally. It was riding on a slab about forty miles thick, and the slab was drifting around on molten glurp. And all the other continents had slabs of their own. When one slab crashed into another one, mountains were made.”

—Kurt Vonnegut, Breakfast of Champions (1973)

Personalized Plates

Sheldon’s knowledge base seems limitless, doesn’t it? He has an eidetic memory, a couple of PhDs, and an IQ of 187, for what that’s worth. Yet, unless you’re very careful, with great intelligence also comes great narcissism. Sheldon means no harm. When he reminds all-comers of his intellectual superiority, he thinks he’s simply stating a fact. Little wonder his close friends get a little tired of his criticisms and his smug statements of sheer fact. Sometimes, though, Sheldon has been shown to be wrong, whether it’s having his physics equations on the whiteboard corrected by Leslie Winkle, losing the Physics Bowl to Leonard’s team, or almost everything he’s ever said about Howard.

One of Sheldon’s greatest errors was on the question of geology. The fact is that geology, in the form of plate tectonics, has revolutionized our understanding of the planet on which we live. Geology has taught us America is getting farther away from Europe, the Pacific is shrinking, and the Red Sea expanding. Through geology we know that the mighty Himalayas will become mightier still and one day the Horn of Africa will be an island.

This geological theory of plate tectonics is a late twentieth-century idea that radically claimed the continents of the Earth were dancing to the tune of deep time. It’s a dance of staggering slowness, yet powerful enough to raise up mountains and pour away the oceans. Geology’s idea is that the Earth’s surface moves on a carpet of molten magma. It accounts for the way in which mountains form and earthquakes shake. It explains the strange spread of fossils across the globe and finally solved the planetary puzzle of why continents like Africa and South America fit snuggly like giant jigsaw pieces.

Even as we speak, Africa is closing in on southern Europe. The Mediterranean, known and loved for romantic holidays, is the remnant of a worldwide super ocean that once encompassed the equator. Indeed, the Mediterranean, this faint echo of a once-great ocean, will vanish in a hundred and fifty million years. In its place will sit a range of mountains, which are already being called the Mediterranean Mountains. In 250 million years, the Mediterranean Mountains will rise up even higher, and the Atlantic will become a paltry little pond, landlocked in a new supercontinent called Ultima Pangaea.

Taking the long and considered view in this way, a view of which Sheldon seems ignorant, explains why plate tectonics has made celebrities out of geologists. They are Rockstar scientists who have helped us profoundly rethink what the Earth was, how it works, and how it influenced the very evolution of homo sapiens.

How’s that for an elevator pitch? Here’s the tectonic backstory.

Maps and Fossils

The idea that the continents may once have fit together like giant jigsaw pieces goes back to the sixteenth century and a Dutch mapmaker named Abraham Ortelius. He’s considered the creator of the first modern atlas and was one of the founders of the Dutch School of Cartography. In fact, Ortelius was so famous he had his portrait painted by Peter Paul Rubens. Most important for our backstory, however, is that Ortelius was the first person to imagine that the continents were once conjoined, before drifting to their present positions. He noticed that the bulge of West Africa looked as though it could have fit into South America. These days, a kid in kindergarten may see the same thing, of course, but you need decent maps to even notice, and Ortelius made very decent maps.

We then have to fast-forward to the early twentieth century before someone actually suggested a mechanism by which the continents might move around. Alfred Wegener was a German geophysicist, which just goes to show physics and geology can work hand in hand. Wegener was a polar explorer who had been involved in several expeditions to Greenland. Explorers like Wegener were hardy creatures indeed. His expedition members were the first to overwinter on the inland Greenland ice sheet, and the first to bore ice cores on a moving Arctic glacier. (Wegener eventually died out on the Greenland ice sheet in 1930, his body and his diary now lying under more than 330 feet of amassed ice and snow. See what is meant by geologists being Rockstar scientists? Live fast, die young!) From 1912, Wegener publicly advocated the existence of “continental drift,” suggesting that all the continents were once conjoined in a single landmass, which had since drifted apart. And it’s with Wegener’s promotion of continental drift that the theory of plate tectonics began to develop.

Wegener was also well aware of a second puzzle, and that’s the question of the fossil and rock distribution around the world. For example, sitting in the strata from what geologists call the Permo-Carboniferous age, from about 300 million years ago, are rocks known as glacial sediments. These sediments are found in places such as South America, Africa, and India. How could these rocks have been laid down at the same time, and yet be so widely separated by a geography that crosses whole continents? The same can be asked about some fossils. The remains of Mesosaurus (“middle lizard”), a freshwater crocodile-like reptile that lived in the Permian period between 286 and 258 million years ago, are found only in Southern Africa and Eastern South America. It would have been impossible for Mesosaurus to swim between the continents, as this reptile was only a little over three feet in length, so the Mesosaurus fossils found by geologists suggested that South America and Africa were joined during the early Permian.

Before plate tectonics really took off, however, it needed one final ingredient. The giant geographical puzzle pieces and the spread of certain fossils surely did suggest that there was a single supercontinent sometime in the distant past, but what truly transformed the topic of tectonics was seafloor spreading, hard evidence of continental drift in action.

Seafloor Spreading

During World War II, American geologist Harry Hammond Hess was also a naval officer. Though later to become a Rear Admiral, Hess became a sea captain on a ship equipped with the new technology of sonar. All through World War II, Hess sailed his ships back and forth across the Pacific, as he had lots of time to make measurements and lots of time to think. So, he set about exploring the Pacific, which had only been done in a rather superficial way before the war. And what Hess found changed the way we think about the planet. By 1960, in a much-celebrated report to the US Navy, Hess advanced the idea that the Earth’s crust was moving laterally away from long, volcanically active oceanic ridges, the process later named as seafloor spreading. These midocean ridges go all the way around the globe, in a similar way to the lines on a tennis ball.

But if the seafloor is spreading, and the Earth’s crust is expanding, there must be some regions where the seafloor is being destroyed. It was soon found that hot material in the bowels of the Earth is what drives seafloor spreading. As that hot material rises to the surface, cooler material sinks down toward the core. This creates a spreading apart at the midocean ridges and a sinking, or subduction, of one part of the crust under another at so-called subduction zones.

So, geologists came up with the idea of plate tectonics, in which the Earth’s crust is divided into huge pieces called plates. The places where the plates meet are cracks known as fault lines. Geologists have found that dramatic volcanoes and earthquakes mostly happen along these fault lines. That’s why one set of cracks, the one that encircles the Pacific Ocean, is also called the Ring of Fire, as it’s a fiery reminder of the mighty Earth below.

To picture all this, it helps to imagine the surface of the Earth as a jigsaw puzzle. The plates are like giant puzzle pieces of land that stretch across the globe, very slowly. These plates, which vary in thickness, are made of lithosphere, which floats on top of the gloopy mantle below, what American science fiction writer Kurt Vonnegut refers to as the “molten glurp” in the quote above.

Plates Made Physicists, Too

Sheldon would no doubt be horrified to learn that geology had a huge impact on human evolution, too. Plate tectonics has influenced life on Earth in many ways. Let’s consider just three stunning examples. First, and way down in the dark deep of the oceans, there’s a very unusual community of organisms living on the midocean ridges. These black smoker communities, so-called because the material pouring out from the center of the Earth is smoking blackly in the water, are believed by many scientists to be the kind of place where life on our planet may have originated.

Second, the movement of the continents has influenced life on Earth by isolating populations and powering evolution. A very good example is the isolation of Australia. The continent of Australia is populated by the marsupials, an unusual type of mammal, which includes kangaroos, koalas, and wombats. Eons ago, Australia separated from Antarctica and South America, and a circum-Antarctic current formed, and Australia drifted away and became geographically isolated. It’s this isolation that allowed the marsupial mammals to evolve into a whole series of parallel niches, but in a different way from their placental mammal cousins in the northern hemisphere.

Third, and most amazingly, geologists have discovered the recipe for making a great ancient civilization on Earth. It seems the most important earthly ingredient for the development of a great ancient civilization was living next to plate boundaries, those regions of the planet where our world is rich in resources. Whether it’s metals or minerals, ancient humans were drawn to the riches that rose up from the deep Earth through the fault lines. It’s a link that led eleven of the thirteen most important ancient civilizations to build their cities close to a plate boundary. And what a list it is. Those eleven civilizations, listed along with their boundary dwelling city-states, are: Roman (Rome), Etruscan (Tarquinia and Veii), Greek (Corinth) and Mycenaean (Mycenae), Minoan (Knossos), South West Asian (Tyre), South West Asian (Jerusalem), Assyrian (Ninevah), Mesopotamian (Ur-Uruk), Persian (Susa), Indus (Mohenjo-Daro), and Aryan India (Hastinapura). Of the thirteen great ancient civilizations, only the Egyptian, based around Memphis, and the Chinese, centered around Zhengahou, are the exceptions that prove the rule. And even then, it must be recognized that Egypt also benefits from plate proximity by being close to the Bronze Age network in trade.

In short, Rockstar geologists have discovered, through plate tectonics, a theory of not only how our world was shaped, but how everything that exists today was created. The rest, as they say, including the evolution of physicists, is history.