Cascadia's Fault - Jerry Thompson [51]
At the very least LaVerne Kulm was right to suspect that in 1970, when several scientific papers based on those first Cascadia mud cores were published, nobody would believe thirteen giant earthquakes had caused thirteen landslides on every major offshore river channel along the Oregon coast. Chris Goldfinger didn’t believe it himself. At least not at first.
Scientists generally don’t trust coincidence, and the absence of a convincing explanation guaranteed that the story told by those mud cores was not over. The final chapter—the way those mysterious layers of gunk from the sea floor eventually changed the history of Cascadia’s fault—started to make more sense to me only after I’d dug up a little background on where all that silt and debris had come from in the first place.
Standing on the South Jetty at the mouth of the Columbia River on a stormy day in January, a person would have to squint to make out details along the far shore. The Cape Disappointment lighthouse would flash a smeary streak of white through sheets of gray, horizontal rain. Then, with another gust, the winter gloom would close in again, making it difficult to see the state of Washington from the Oregon side. At this point, the river is four miles (6.4 km) wide.
A few hardy souls, storm watchers who love nothing more than the wet sting of salty wind on their cheeks, can nearly always be found here clinging to the guardrail around the viewing platform at Fort Stevens State Park, their exhilarated or foolish companions leaning into the gusts and grinning at the ferocity of it all. The Columbia River’s freshet fighting an incoming Pacific tide is an impressive sight.
Unlike most other big rivers, the Columbia has no delta to speak of, no meandering Mississippi mud flats, no maze of trackless swamps. Hemmed in by hard rock mountains that were pushed up by plate tectonics, the river chews like a chainsaw through steep, stony canyons and then gushes headlong into the open Pacific. Columbia’s estuary is more compact than a river this size would normally be. Much of the mud that might have formed a sprawling delta in less vertical terrain gets dumped almost directly into the sea.
Suspended in its swollen belly, the river carries silt, sand, and forest debris from 258,000 square miles (668,000 km2) of western mountains that are slowly dissolving under millions of years of rain, rock-splitting ice, and heavy snow. Along the way a host of smaller streams and rivers—the Kootenay, the Pend Oreille, the Snake, the Kicking Horse, the Kettle, the Cowlitz, and many others—add their contributions to the flow and the silt load. At Portland the Columbia inhales the Willamette River, swings north to find a gap between the Coast Range and Olympic Mountains, and then turns west one last time for its final plunge to the sea. The big river’s muddy torrent sweeps past the outport town of Astoria, dumping about 265,000 cubic feet (7,500 m3) of fresh water into the snarly North Pacific every second.
The ocean fights back with tremendous swells, pounding surf, and a tidal surge that will not be denied. At the point roughly five miles (8 km) offshore where these two irresistible forces meet and do battle—the infamous Columbia Bar—a never-ending churn between outgoing river and incoming tide, amplified by howling winds—creates standing waves as high as thirty feet (9 m). Having reached the horizontal plane of the sea after more than a thousand downhill miles (1,600 km), the river slows and begins dumping its cargo of suspended debris in a constantly shifting barricade of sandbars and shoals that make the mouth of the river one of the most hazardous places in the world for mariners. Some say nearly two thousand ships and boats have been wrecked along this stretch of the coast—nicknamed the Graveyard of the Pacific—over the