If you head east out of Las Vegas on the interstate and take the exit for 93 North you will quickly spy one of my favorite road signs in the United States: “The Great Basin Highway.” By modern standards 93 is not exactly a highway but it is a marvelous long stretch of fast two-lane blacktop that runs through some grand and startling scenery.
An abandoned miner's cottage east of US 93
I imagine most who drive the quiet road are unaware that about 370 million years ago they would have been traveling through a warm, shallow sea, speckled with coral reefs, thriving with life. Fewer still will realize that once they pass Hancock Summit, where the road climbs sharply, bends, and then heads, unnervingly straight, to the north, they are entering the remains of a truly gigantic and ancient meteorite crater.
Most meteorites are rich in the element iron, so prolonged exposure to terrestrial elements will cause them to decay. The meteorite that crashed here, before mammals and birds learned to walk and fly, is long gone, but it leaves the traces of its passing within the hills and mountains of Lincoln County.
Mine workings on a precipice in the Nevada Mountains
A breccia (pronounced “brech — ee — uh”) is a rock composed of fragments of other rocks, cemented together. When a large meteorite hits our planet, shatters the target rock at the point of impact, and the resulting mixed-up pieces are compacted together by heat and pressure, an impact breccia is formed. If you climb far enough up into the hills around Tempiute Mountain, Nevada, and know where to look, you’ll see a profusion of them.
An outcrop of the Alamo impact breccia in the Nevada mountains. The rock hammer is included for scale.
Named after a nearby town, the Alamo Breccia covers an area of hundreds of square miles, making it one of the world’s largest remnant meteorite craters. The inferno that followed the impact must have exterminated all life for scores of miles in every direction. An atomic bomb would have been a firework in comparison. The meteorite slammed into the long-vanished ocean, and exploded among the coral reefs. Tiny fossils, embedded in the breccia, tell the story. To learn more about impactites see “Ghostly Footprints of Ancient Meteorites” on Geology.com.
Once below sea level, the Alamo layer has been raised thousands of feet and exposed, in places, by geological processes. To the casual observer, the breccia layer might appear much like any other stratum of ordinary rock, but a studied look will reveal a multi-colored kaleidoscope of angular fragments, pulverized by a cataclysmic meteoritic event. When cut and polished, the Alamo Breccia is as lovely as a Paul Klee painting. And it takes a feat of imagination to peer from a mountainside at 8,000 feet, then tell yourself you are standing on something that once lay at the bottom of a submerged crater.
A cut and polished section of the Alamo Breccia. The white area, bottom left, is fossil coral. Photograph by Leigh Anne DelRay.
I recently returned from my fourth visit to the Alamo Breccia site. Usually, not much changes up there in the Nevada mountains, in terms of human time at least. But I noted with interest a couple of new mines, perched most precariously on steep and dangerous cliff faces. How did they get all the equipment up there? Mules? Even my sturdy 4WD Tacoma, veteran of many a scary off-road moment, could not possibly make the trip; it is a demanding hike on steep and treacherous trails.
With their diminutive railroad tracks, and Seven Dwarves-sized entrances, those hidden mines looked like something out of a classic western film. I immediately thought of bears, then rattlesnakes, and finally mountain lions, but recklessly crept inside two of mine entrances anyway. I half expected to see Walter Huston and Humphrey Bogart hunched in the darkness, tending a small fire and arguing about how to divide up the gold.
Spooky mine entrance near Tempiute Mountain, Nevada
They don’t make movies like Treasure of the Sierra Madre anymore, but one thing holds true: Wherever there are valuable rocks, no matter how difficult they may be to reach, some enterprising prospector will stake a claim and eke a hard living out of the buried veins.
All photographs by the author unless otherwise noted. © Geoffrey Notkin. All rights reserved, copyright strictly enforced.