How do the Middle Cascades differ from the South Cascades?

The Middle and South Cascades differ primarily in their geological formation and structural history.

The Middle Cascades, which extend from west-central Washington into Oregon, are characterized as an uplifted and faulted region composed of Cenozoic Era volcanics, including layers of tuffs, breccias, mudflows, and basaltic flows.1

In contrast, the South Cascades, which stretch from southern Oregon into northern California, are distinguished by the fact that they were not uplifted. Despite this difference in tectonic history, the South Cascades are still home to significant volcanic features, most notably Mount Shasta and Lassen Peak. Additionally, the South Cascades are traversed by the Pit River, which provides a low-elevation passage through the range.1