The Wyoming we see today was sculpted in the blink of an eye, geologically speaking. The landscape is the result of an erosive process triggered by a massive uplift of the western part of the North American continent. All of this has taken place within the past three million years.
The uplift caused peaceful rivers, meandering in well-established patterns across flat terrain, to speed up their flow. Soon they became rushing streams, cutting down through layers of soft, sedimentary rock, then into harder igneous and metamorphic rock that formed the core of long-buried Rocky Mountain ranges.
Assisted by wind, ice and other forces of erosion, the rivers slowly exhume the mountains, carve the canyons and excavate the great basins so familiar in this high, wide-open state. Evidence of Wyoming's earlier and higher surface landscape can still be seen as the tops of a few scattered land features that the erosion process missed. Table Mountain south of Lander, the Pumpkin Buttes near Gillette, Crowheart Butte east of Dubois and Pilot Butte north of Rock Springs are but a few examples.
But that's all recent geological history of events that took place from the late Pliocene Epoch to the present – a time when Wyoming's climate changed from temperate to an ice age and back. It was a time when construction of the Teton Mountains was almost complete and the Yellowstone region was being rocked by another series of violent volcanic explosions and lava flows that would form today's massive calderas and plateaus.
Great seas covered all or parts of the state at different times. When the seas occasionally receded, the exposed land was relatively level and featureless except for an ancestral mountain building process that involved southeastern Wyoming during the Pennsylvanian period. The climate remained mild and the vegetation tropical. Over the eons, huge amounts of silt were deposited at the bottom of the seas. They eventually compressed and solidified into layers of colorful sedimentary sandstone, limestone and shale thousands of feet thick. Later, these layers bent, folded, broke, tilted and eroded during the mountain building process. Today, travelers can read these layers, exposed on mountainsides and canyon walls, like a geological calendar.
Within the last 200,000 years, massive glaciers formed in the state's towering mountains to complete the sculpting job started by wind and water.
Since most of Yellowstone's 350 miles of roads are closed to cars from November through April, getting into the park, be it to Old Faithful, Norris Geyser Basin or Yellowstone Lake, is a bit more of an adventure come winter. The park itself isn't closed of course – there are still entrance fees and lodges, hotels, restaurants, bars and gift shops are open – it's just that the only ways to get inside are by ski, snowshoe, snowcoach or snowmobile. read more
Rub your hand on an aspen tree, and it will come away powdery white. These ghostly trees with their white bark and black knots or branches have nearly round leaves that are green and supple in the spring and summer. But when the weather turns colder in early September, these round leaves begin to change colors, turning yellow, then bright gold, often deep red. read more
