Excerpts

Their Campsite, Our Core Picture a campsite-one of the standard-issue kinds replicated in national forests and parks around the country. In a lot of ways, it's the quintessential American image: the kind of image you'd find on a postage stamp or in an ad for a new made-in-the-USA truck or maybe even in your favorite Brady Bunch episode. In so many ways, these sites represent our collective values: After all, these campgrounds exist because of good national policy, good government-real bedrock stuff. At the particular site I have in mind, there's a little gravel pull-off for a vehicle and a bare pad just large enough for a four-person tent. Off to the side, a picnic table cozies up to a well-used fire ring lined with blackened stones. Maybe you've slept at sites like this. Perhaps you and your kids have roasted marshmallows in that fire ring, feeling the chipped paint of the picnic table on bare legs as you stretched toasting sticks into the embers, liking the way the soles of your shoes heated up on the rocks. Even if you haven't actually done this, I bet you can still imagine it. Why? Because it is a deeply American scene: "Go West, young man" meets wholesome family togetherness, complete with hot dogs and Jiffy Pop. Now imagine the force required to cleave that land-to strike a fissure between that picnic table and fire ring. One moment, the two objects sit side by side, just a few feet separating them. The next moment, the fire ring and everything to the east of it drops twenty feet. Your toes are no longer touching warm stones. They're dangling off a cliff. This scenario sounds like the sort of thing that can only happen in Hollywood. But sixty years ago, that's precisely what happened at the Cabin Creek Campground, just outside Yellowstone National Park. On August 17, 1959, a magnitude 7.5 earthquake ruptured with an epicenter just a few miles from there. The sheer force of that rupture caused the land to split and half of the site to plummet in what geologists call a scarp, or a sharp line of cliffs caused by seismic activity. As terrifying as that would have been for anyone there, it was the least of the damage to the area: Just across the river, the nation's biggest recorded rock slide-over 73 million metric tons of debris-roared down a canyon wall, burying nineteen people. They were never recovered. At least nine other victims died of their injuries. Today, a massive lake rests where their campsites once stood. Nearby, you can find geysers and fissures and sinkholes where there were none-all because of this single earthquake. You can be forgiven for thinking that the ground beneath your feet is solid. For most of us, it certainly appears as much. When I was seven, I ran away with my motherÕs formal silverware, wrongly thinking there was a utensil shortage in China. Because I knew that the shortest distance between two points was a straight line, I also took my dadÕs shovel, figuring I could dig my way there in a couple of days. I lasted about an hour before I hit the dense clay that makes up so much of the Mississippi River corridor. To my scrawny arms, it was impenetrable. I assumed everything below it was equally unyielding. And so I returned home, defeated, before anyone had even noticed that the silver and I were missing. If basic earth science had been covered in my first grade curriculum, I'd like to think I wouldn't have bothered with the shovel. Maybe you remember that iconic drawing of the planet cut into a cross section that's often used in geology textbooks. I always think it looks like a peach: thin outer skin, flesh that's not quite solid or liquid, a tidy pit. That outer layer, insofar as the planet is concerned, is called the crust. This is a misleading term. It's actually made up of a bunch of jagged pieces known as plates. The current best guess is that, right now, there are fifteen big ones and a handful of smaller ones floating around. The thicker and less dense ones are known as continental plates. The heavier ones are oceanic. We'll talk more about each in the next chapter. What's important to know now is that these plates, which are forever in motion themselves, also bear the scars of billions of years of upheaval and trauma on this planet. For instance, beginning near Lake Superior, there's a 1000-mile forked crack down the center of this country known as the Midcontinent Rift. One tine of this crack snakes down to Oklahoma. The other works its way clear to Alabama. This rift exists because, about a billion years ago, the continent began to break apart. Scientists aren't sure why the rift began to form, though they think it might have been because of volcanic activity below it. Even more puzzling to them is why we're still in one piece (a similar rift threading through East Africa appears to be succeeding in ripping that continent in two). Other marks are no less monumental. The Appalachian Mountains, the oldest on the planet, are actually scabs from a head-on collision of two plates. They are composed largely of rock that once made up the seafloor-and they were once taller than the Himalayas. This kind of dramatic shifting happens on our planet all the time. While I was writing this chapter, a new island, about a half mile wide, popped up just south of Fiji, thanks to an active volcano there. Another one appeared off the coast of Japan in 2013. Meanwhile, a new plate appears to be forming below the Indian Ocean, perhaps birthed by the 2012 Sumatran earthquakes. While all this activity is visible on the crust, most of it is actually caused by what lies just underneath: the mantle, which is a combination of solid and liquid rock. The mantle makes up most of our planet's volume, and there's a huge variation in its temperature from top to bottom. Up near the crust, it's a cool 1800¡F. As you plunge deeper, it reaches a temperature of almost 7000¡F. (Silver, incidentally melts at 1763¡F, which is just one reason why my chosen path to China was a bad one-at least where the longevity of my mother's salad forks was concerned.) This difference in temperature between the outer and inner mantle creates a dynamic heat exchange as hotter rock and magma rise to the surface and cooler rock falls back down. Want to see this in practice? Think of a lava lamp. Or, if that's too groovy for you, dump a can of minestrone into a pot and watch it boil on the stove. There's a certain rhythm to the rotation of carrots and macaroni as they are pushed to the surface and then back down again to the bottom of the pot. It's mesmerizing-at least until you remember that we're floating on top of a very similar process. Soup eaters or not, seismologists love the mantle. It's where everything happens in one big, dynamic mess. Parts of the mantle are solid. Some of it is plastic or even viscous. Its movement is responsible for the drifting and colliding of our plates. Earthquakes occur there. Below the mantle lies the core, which is probably the least interesting layer for any book about seismicity. First discovered in 1936, it's also the least understood. What is known is that the core is made up mostly of nickel and iron and is divided into two parts-the outer, which is molten, and the inner, which is solid but only because it is under immense pressure. It is also the very hottest part of our planet-scientists think it's temperature is probably between 9,000 and 13,000¡F (by comparison, the sun's chromosphere-the deepest layer we can currently observe-ranges between 6,700 and 11,000¡F). To reach the middle of the earth's core, you'd have to travel down about 3400 miles. Then you'd have to go back up about another 3400 miles if you wanted to pop out on the other side of the planet. (It's about 6500 miles from Davenport, Iowa, to Beijing overland, which is yet one more reason my silverware reallocation plan was a lousy one.) If you've been counting, I've already used the word "about" eight times in this chapter alone. It's a word you hear even more frequently among scientists who study the inner workings of our planet. In the past decade or so, they've come up with some sophisticated tools to help them visualize what's going on below us, including 3-D imaging techniques. Nevertheless, saying this instrumentation gives us any kind of definitive knowledge about what goes on inside the earth is a lot like saying you've mastered the inner workings of a human body because you've seen an X-ray or CAT scan. You might have a decent idea of what's in there, but you're missing a lot of nuance. Where geology is concerned, these gaps are not for lack of trying. In 1958, a group of American scientists attempted to drill into the place where the crust and mantle meet, which also, incidentally, is the place where most of our seismic activity occurs. Geologists call this boundary the Mohorovicic discontinuity, so named for Andrija Mohorovicic, the Croatian seismologist who discovered it in the early 1900s. (Pro tip: If you want to look like you know what you're doing at a seismology conference, refer to this space as "the Moho.") Like the crust, the Moho is far from uniform. On average, it tends to sit about five miles below the ocean floor and twenty miles below any continent. If you want to find it, you'd be much better off looking under an ocean instead of, say, Cleveland. At least, that's what Walter Munk figured. A Vienna-born scientist who studied in the United States and applied for American citizenship after the Anschluss, Munk made a name for himself in World War II by correctly projecting wave heights, which allowed more than 160,000 Allies to land on the shores of Normandy during D-day. In the years immediately after the war, Munk played an integral role in our nation's early nuclear testing on Pacific atolls. His job? To look for and measure tsunamis created by the blasts. After that gig, Munk proposed Project Mohole: an attempt to drill into the Moho layer at depth. The project was endorsed by the American Miscellaneous Society, the loosest possible consortium of scientists: AMSOC, writes geologist and oceanographer Kenneth Hsu, "had no statutes or bylaws, no official membership, no officers, no formal meetings, no proceedings." Any scientist could become a member merely by saying so. The primary function of AMSOC was to support projects that had been rejected by other agencies, most notably the Office of Naval Research. Munk figured they were just the group to get behind his project. And so, one morning in the spring of 1957, he invited a few geology and oceanography friends over for breakfast. They appointed themselves an official AMSOC subcommittee. Together, they also submitted their Mohole proposal to the organization as a whole. The rest of AMSOC loved it. Theirs was maybe not the most prestigious endorsement for a project, but it nevertheless helped persuade the National Science Foundation to fund Project Mohole. As presented, Munk's plan was a three-tiered attempt to bore below the earth's crust off the coast of Guadalupe, Mexico. This proposal raised no small amount of controversy in the geological world. Young radicals like Hsu tended to love it. Members of the establishment thought it was an absurd waste of money. The Mohole group managed to overcome enough dissent and technical difficulties to begin their project. They succeeded in drilling down through the ocean floor about 600 feet before internal conflicts in the Miscellaneous Society led to its disbandment. The National Academy of Sciences took over the project in 1964. By then, the project's tab was over $1.8 million. Estimates for what it would take to finish the job were $68 million. That was a hard number for Congress to swallow. They cut off funding two years later. The Soviet Union began a similar project in 1970 known as the Kola Superdeep Borehole. They made it down about 7.5 miles before incredible heat (about 350¡F) basically melted their drill bits. Team scientists tried a variety of different solutions, but eventually the problem of temperature proved too much. There is no easy way to get to the Kola Peninsula, which lies near the top of Finland and entirely above the Arctic Circle. If you're willing to take eighteen hours' worth of flights on increasingly dubious-looking airplanes, followed by a very confused SUV ride across the tundra, you'll eventually reach the weirdly bombed-out remains of the dig site, which includes no small amount of discarded equipment and trash littered around. The actual borehole, which is just nine inches wide, is covered by a rusted cap. At the end of the project, engineers welded it shut and added twelve enormous bolts for extra measure. Even if you were able to remove them, you wouldn't find the Moho: The borehole got only about a third of the way down. 1 If you really want to see whatÕs going on inside our planet, your best bet is to go to places like Yellowstone National Park. There, you donÕt have to drill down thirty miles to see the guts of the planet. Instead, they come to you. The park itself actually sits in a caldera, a giant sinkhole created during a massive volcanic eruption. The caldera is what scientists sometimes call a Òsupervolcano.Ó While not actually a scientific term, that is the word scientists use to categorize any volcano capable of spewing a trillion tons or more of ash and debris in an eruption. Worldwide, there are only about a dozen supervolcanoes capable of that kind of explosion. Yellowstone is one of the biggest. Just over 2 million years ago, it erupted and spewed more than 585 cubic miles of magma-about 200 times more than Krakatau in its epic 1883 eruption. That same Yellowstone eruption left an enormous ash bed that blanketed much of what is currently the United States. Think of an equilateral triangle with its top in Winnipeg and two bottom corners in San Diego and New Orleans, respectively. ThatÕs how far the ash spread. Fueling Yellowstone today are two reservoirs of magma. Geologists call these reservoirs "blobs" (that's a technical term). They're still not sure just how much magma is in those reservoirs, but current best guesses are that the two blobs probably total about 35,000 cubic miles of magma. For comparison's sake, it takes about 2900 cubic miles to fill Lake Superior. In general, magma tends to stay deep within the earth. Most of our planet's volcanoes occur in places where two plates meet and one slides under the other (what geologists call a subduction zone). That sliding melts the otherwise solid mantle and allows a column of magma to escape. The Pacific Ocean's Ring of Fire is a great example of this process in action. So is Mount Saint Helens, which is also located on a subduction zone. Yellowstone, on the other hand, is smack-dab in the middle of a continent. So how did it come to be? Excerpted from Quakeland: Preparing for America's Next Devastating Earthquake by Kathryn Miles All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.