Genealogy of the West’s landscape
In “Rough-Hewn Land,” Keith Heyer Meldahl takes us on a field trip from San Francisco to the Rocky Mountains, tracing the genealogy of the landscape. He seasons the story with historical accounts and a synthesis of evolving geologic theory, providing a fascinating guide to the formation of the West.
“Geology,” Meldahl writes, “is stranger than fiction.” How did material that was once buried miles beneath the Pacific seabed in the deep ocean wind up a rock in the Sierra Nevada with a pine tree poking out of it? How did the Rockies, far from the classic mountain-building forces of the continental edge, get tall enough to leave hikers gasping for oxygen?
The answers lie in the ancient forces of plate tectonics, volcanism and upheaval that birthed the West and continue to shape it. If there is an overarching theme of the book, it is that the region remains geologically alive.
The Pacific Plate, which includes coastal Southern California, is creeping to the Northwest at a rate of about 2 inches a year. The Great Basin is stretching, annually adding a half-inch to the distance between Reno and Salt Lake City. In 1872, the Sierra Nevada in an instant lurched 6 feet when one of the most violent earthquakes in California’s recorded history jolted the Owens Valley, nearly leveling Lone Pine and killing more than two dozen residents.
Fittingly for a state full of immigrants, it turns out that, geologically speaking, California isn’t native either. “Wherever you stand in this state, if your feet are on bedrock, the odds are that you’re standing on an immigrant, reeled in by subduction from the far reaches of the Pacific in the process of assembling California,” writes Meldahl, a geology professor at MiraCosta College in San Diego County.
As the Pacific floor spread, fed by lava welling up from midocean ridges, it collided with the westward-creeping North American plate and plunged under it. During the last 200 million years, ancient seabed was scraped off and left behind, attaching itself to the continent’s edge and incrementally building the Golden State.
