I drove from Helena, Montana to Boise, Idaho to get between work locations. It was one of the longest drives I’ve ever made between two job sites. The drive is beautiful, through the mountains south of Butte, MT and then west hugging the mountains along the north side of the Snake River Plain. I added a short stop to see Craters of the Moon National Monument. This is not an every day drive. Most people will never make the drive across southern Idaho. I’ll probably never do it again. That’s why I wanted to highlight it. Below is a photo tour of the drive with a brief discussion of the geology of the Snake River Plain and Craters of the Moon.
Road trips up and down the East Coast and mid-Atlantic or crossing the Midwest are monotonous and boring. Road trips through the mountain west are scenic and enjoyable. The landscapes are big, contrasting, and seem never-ending. For me, understanding the geology helps appreciate the geography, changes in topography and scenery. You can tell the story of a landscape through its geology; incorporating time, mineralogy, structure, tectonics. It actually gives geology a bit of creativity as a science. You are telling stories of something that happened thousands to millions to billions of years ago. You can’t see what happened. But with understanding of geologic processes and some imagination, you can tell the story.
The Snake River Plain is a flat, bow-shaped plain, surrounded by mountains, that covers southern Idaho. The western plain is a tectonic rift valley. It is part of the northern edge of the Basin and Range Province. The central and eastern part of the plain is almost entire volcanic, due to the expansion of the crust. You may be familiar with the geothermal activity in Yellowstone National Park. The hot spot that creates the geysers and hot pools in Yellowstone today, created the volcanic activity in the Snake River plain over the past 10-12 million years. I you want more about the Snake River Plain Geology, the Craters of the Moon is a good place to start.
Here is a look on the drive from Montana, south on I-15, and then hugging the mountains along the north side of the Snake River Pain, on the way to Boise.