Making the Rocks Talk

The New York Times, July 25, 2004

SIMON LAMB, a geologist at Oxford University, got a call one day from a television producer about pictures of Atlantis. The lost civilization could be found on 12,000-foot high plains nestled in the Andes Mountains. An Atlantis expert (whatever that is) had shown the producer satellite photographs of the plains, pointing out canals running in parallel straight lines for miles. What more proof could one ask for? The producer called Lamb, an expert on the Andes, for confirmation.

Lamb pulled out his own satellite photographs, found the canals, and laughed. He told the producer that canals had formed naturally, without any help from Atlanteans. Hundreds of millions of years ago, before the Andes existed, rocks had slowly piled up in layers. Later the rocks were heaved onto their side and raised up thousands of feet, whereupon rain began to flow down their exposed flanks. The water gnawed away at the weakest layers, creating a series of straight-edged channels. As he spoke, Lamb could sense hostility on the other end of the line. The producer didn’t want to hear about strata and erosion. “Well, that’s your explanation, anyway,” he huffed, and went off to make his documentary without Lamb’s help. “Atlantis in the Andes” later appeared on the Learning Channel.

This story has a silver lining. The conversation inspired Lamb to demonstrate just how fascinating the Atlantis-free Andes are. The result is “Devil in the Mountain,” an absorbing account of the many years Lamb has spent exploring and pondering the Andes. But the book is not simply about a particular place or one scientific career. Lamb gives his readers a wonderful feel for how geology works — how geologists gather clues, test hypotheses and ultimately come to understand the workings of the world.

He walks in some pretty big footprints. Charles Darwin visited the Andes in 1835 during his voyage on H.M.S. Beagle. An earthquake shook Chile while he was there, and Darwin discovered it had lifted miles of coastline 10 feet out of the sea. On a mountain hike, he discovered seashells embedded in rocks at more than 6,000 feet. He proposed that over millions of years the mountains had been lifted up from the sea by quakes such as the one he had seen. Now rain was gently sanding the mountains down and might some day help wipe them away. “Nothing, not even the wind that blows, is so unstable as the level of the crust of this earth,” Darwin wrote.

The idea was a radical one, as radical as Darwin’s theory of evolution. But later generations of geologists demonstrated that he was fundamentally right. In the 1960’s their research flowered into the theory of plate tectonics. The surface of the earth is divided into giant plates that move like conveyor belts. Hot rock rising from the earth’s interior adds a fresh margin to one edge of each plate. Meanwhile, the old rock at the other end of the plate sinks back down into the earth’s interior, where it melts away.

By the time Lamb started his career in the late 1980’s, plate tectonics had gone from controversial to conventional. What was left for a young geologist to discover? Plenty. Why, for example, are the Andes so big and so high? They form a spine along the western edge of South America, where one of the crustal plates of the Pacific Ocean dives underneath the continent. All the other mountain ranges in the same sort of location (in New Zealand or Alaska, for example) are puny by comparison. Lamb recognized that the answer to this question would require more than a simple model of a conveyor belt.

Lamb set out to find the answer. Since 1989 he and his coworkers have driven 100,000 miles inspecting the mountains, mostly in Bolivia, home to the highest peaks (and those canal-scarred plains). In “Devil in the Mountain,” he describes some of these trips and his research. On some expeditions he simply made sketches in notebooks. On others he stood waist-deep in rivers, drilling out cylinders of rock with a diamond-tipped corer. Sometimes he scrambled up volcanoes to capture gas that had risen hundreds of miles from below the earth’s crust.

Rock by rock, page by page, a picture gradually emerges. The tracks of dinosaurs made in a flat muddy plain tell Lamb there were no Andes mountains 70 million years ago. He explains how he tracked the rise of the mountains starting about 40 million years ago by mapping the routes of the rivers of that age. Fossils of leaves help reveal the altitude of the mountains, rising from the wet tropics up above the cold tree line. In just the last 10 million years, Lamb finds, parts of the Andes have doubled in height.

He not only maps the rise of the Andes but finds evidence of what makes them rise. The plate diving under South America (called the Nazca plate) is driving hot rock upward, bulking up the mountains. At the same time, it pushes against South America, raising mountains higher as they fold like an accordion. The Nazca rams against South America with exceptional force, and Lamb proposes that this is because it can’t slip smoothly underneath the continent. Other sinking plates are greased with sediments carried to the sea floor by rivers. But the land closest to the Nazca plate — the continent’s western coast — is home to the driest deserts on earth. This peculiar situation is the result of climate change, according to Lamb: over the past 40 million years the earth has cooled, and one result has been the drying up of western South America, along with the creation of one of the world’s greatest mountain ranges.

“Devil in the Mountain” isn’t perfect, but it succeeds in its main mission, to make us so familiar with the history of the Andes that they become living things. The mountains start out like children growing fast, rising from the shore. We watch them mature into broad high ranges, before winding up today in a sort of geological middle age, their soaring growth overcome by sagging foundations and the ravages of erosion. Lamb’s book is a welcome relief from the geological ignorance on parade these days. Almost half of Americans say they believe God created humans pretty much in our present form at one time within the last 10,000 years. At the Grand Canyon, the National Park Service’s bookstores stock a book that claims the canyon was carved by Noah’s Flood. Despite protests from the Park Service’s own geologists, it remains on the shelves, and sales are reportedly brisk. Here’s hoping “Devil in the Mountain” sells even more copies. At the very least, everyone who watched “Atlantis in the Andes” should have to buy one.