Fifty Million Years of Basin and Range, The Geology Under Everything

Look at Nevada from the air and you see it immediately: long, dark ridgelines running north to south, separated by broad pale valleys, over and over, the whole state from corner to corner. That alternating pattern of mountain and flat, ridge and valley, is not random. It is the signature of one of the most dramatic geological processes on the continent, still active, still ongoing.

About seventeen million years ago, the crust beneath the Great Basin began to stretch. The North American plate was being pulled apart at its own interior, and the surface cracked into tilted blocks, some rising to form the ranges, others dropping to form the basins. Geologists call it basin and range extension, and Nevada sits at its heart.

The state has more individual mountain ranges than any other in the continental United States, somewhere around three hundred and fifteen of them. Most are under a hundred miles long. Between each pair lies a flat-floored valley that was once, in wetter times, a lake.

Those ancient lakes were real. Lake Lahontan covered most of western Nevada during the last ice age, a body of water roughly the size of present-day Lake Erie, fed by glacial melt from the Sierra Nevada and the Ruby Mountains. Pyramid Lake and Walker Lake are what is left of it, the lowest points where water still collects in a system that has been draining and shrinking for twelve thousand years.

The silver that built Virginia City and financed the Union was deposited by hydrothermal fluids moving through fault zones in these same tilted blocks, tens of millions of years ago. The gold at Carlin, the lithium in Clayton Valley, the copper at Ely, all of it traces back to the same restless geology. Nevada does not have natural resources despite its landscape.

It has them because of it.