Is 500,000,000 years far back enough?
Half a billion (or so) years ago, Nevada rested underwater. At least twice during the long Paleozoic Era (340 million years), violent and titanic episodes of uplift raised the ocean floor, drained the sea, and left towering mesas and alluvial plains. Over the next 160 million years, cataclysmic extinctions, volcanism, and climatic crises, punctuated by long periods of erosion, continually altered Nevada, several times obliterating its life and landscape.
Seventeen million years ago, today’s familiar basins and ranges were created by the colossal jostle of tectonic forces. More than 250 separate mountain ranges are currently named in Nevada. Ninety percent of them are oriented northeast-southwest, and on a relief map they look like a herd of earthworms marching toward Mexico. The southwest-trending cavalcade of ranges, however, jams up at a southeast-trending dead end at the northern edge of Las Vegas Valley. Geologists refer to this phenomenon (apparently without irony) as the Las Vegas Zone of Deformation.
Beginning nearly two million years ago, four great ice ages advanced into and retreated from history. Nevada’s Basin and Range Physiographic Province, which had been shuffled by earthquakes, tilted by crustal adjustments, and whittled by erosion, was now alternately drowned, drained, and ground down by glaciers. By the end of the last ice age, 12,000 years ago, Las Vegas Valley had finally taken the shape it retains today: relatively long and flat, cutting an 18- by 26-mile diagonal across Clark County, near the southern tip of the state.
Over the millennia, alluvial fans of stone, gravel, and cobble spread down from the mountains onto the valley floor, creating a concrete-like lake-bottom hardpan known as caliche -- these days the scourge of the area’s construction companies, swimming-pool installers, and gardeners. Underneath that used to be a major system of artesian aquifers, which was tapped as high as 40 feet and as low as 1,000. Before the drastic depletion of the local aquifer in the 1930s, artesian pressure forced this water up to the surface of the valley, creating what came to be known as Big Springs, an oasis of tall grasses, mesquite, and cottonwoods, with several short creeks flowing from it, which converged into the Las Vegas Wash and flowed southeast into the Colorado River (as storm drainage does today into Lake Mead).
People inhabited Las Vegas Valley as early as 13,000 years ago, at the cold and wet tail end of the Wisconsin Ice Age. These Paleo-Indians lived in shoreline caves and hunted the large Pleistocene mammals -- wooly mammoth, mastodon, bison, even caribou -- that disappeared from the area as it dried out over a few thousand years. Excavations at Tule Springs, an archeological site in the northwestern valley (now Floyd Lamb State Park), have uncovered prehistoric hearths, fluted arrows and spear points, scraping tools, and scarred and charred animal bones.
Roughly 4,500 years ago, the Archaic or Desert people arrived. They evolved a forager culture, adapting to the use of such high-quality but limited resources as the desert tortoise, bighorn sheep, screwbean mesquite, canyon grape, and cholla fruit. The settlers lived in small groups, scattered from the valleys to the peaks, their numbers growing or shrinking according to abundance or scarcity. They built rock shelters, circular stone campsites, and roasting pits, and used the atlatl (a primitive but efficient arrow-throwing stick), mortars and pestles, flaked knives, and hammerstones. These Archaics could be considered the cultural ancestors of the later Paiute people.
Around 1700 years ago, a new culture, the Basketmakers, appeared in the Las Vegas area. Also hunter-foragers, they were more sophisticated than their predecessors in only one respect. They lived in pit houses: three- to four-feet deep excavations, with mud floors and walls, brush roofs supported by strong poles, and a central fire pit.
By the year 500 or so, the Modified Basketmaker period began, perhaps introduced by Pueblo pioneers migrating to their western frontier. Within two centuries, these ancestral Puebloans -- also known as Anasazi (a Navajo term for "Enemies of our Ancestors") were settled primarily in the fertile permanently in the fertile river valleys of what is now southeastern Nevada.
The Anasazi and subsequent Pauite peoples require long enough stories that they’re an answer for another Question of the Day.
