The Intermontane Plateaus

Intermontane Plateaus Region is located in the Western part of the United States. Some people refer to it, or parts of it, as the Intermountain West (Hardwick). There are both mountain ranges and plateaus located there, and the entire area is subdivided into physiographic provinces. These provinces are further subdivided, down into sections. The provinces are the Columbia Plateau Province, the Colorado Plateau Province, the Basin and Range Province, and the Intermediate Province (Hardwick). All are important to the landscape and ecosystem of the area, and all are different when it comes to how they were formed and what they have to offer in the way of terrain. The Columbia Plateau comprises much of Oregon, Washington, California, Idaho, and Nevada (Hardwick). It is primarily igneous, and there are also flood basalts located there. It was first formed during the Miocene and Pliocene periods (USGS).

In contrast to that, the Colorado Plateau is west of the Southern part of the Rocky Mountains. Utah, New Mexico, Colorado, and Arizona all contain parts of it (Hardwick). Large-textured forms are the main characteristic of that plateau, which was formed during Paleozoic, Tertiary, and Mesozoic time periods (USGS). The climate is also very dry there, which affects not only how the area was formed, but how it changes and evolves over time, even in the modern day. The dryness of the area makes it difficult for agriculture there, along with the raising of livestock. However, there are nearby areas where this can more easily take place, because the terrain is slightly different.

The Basin and Range Province makes up parts of Idaho, Oregon, California, Utah, Nevada, Arizona, and New Mexico (Hardwick). It also extends into Mexico, most specifically in the Mexican states of Sinaloa, Chihuahua, and Sonora (Hardwick). There are many ancient folds and faults to be found in this region, including some that reach all the way back to the Jurassic period (USGS). Differences in the way the area has aged and worn can be seen from the north to the south, with the southern areas being flatter and more eroded than the areas that are further north. Alluvial fans are also seen more often in the southernmost parts of that particular province (Hardwick).

The Intermediate Province is smaller, in that only parts of Idaho, Washington, and Oregon are located within it (Hardwick). One of the most striking areas to be considered within that province are the lava fields that are seen in the Columbia River Basin area (Hardwick). These fields are more than 4,000 feet deep in places, and cover nearly 200,000 square meters (Hardwick). They are among the largest and most extensive volcanic fields to be found anywhere in the world, making them valuable to study and an anomaly when compared to the areas around them. Any of the land forms that existed there before the lava flows occurred are completely buried, so it is not possible to tell what the land looked like before the volcanic eruption that made the massive flows. River canyons are also present throughout the area, and while there are few trees in the actual lava plains, there is wildlife to be found. They also support horses and cattle, but are too dry for agriculture (Hardwick).