How does the Sierra Nevada connect geologically to the Cascade Range?

The Sierra Nevada and the Cascade Range are distinct mountain systems that differ significantly in their geologic composition and formation. While the Sierra Nevada is primarily an upfaulted block composed largely of granite, the Cascades are defined by volcanic activity and lava outpourings.12

Geologically, these two ranges connect at the northern limit of the Sierra Nevada. In this region, the granitic and metamorphic rocks characteristic of the northern Sierras merge with the volcanic rocks that dominate the Cascade Range. Beyond this transition, the two ranges remain geographically continuous, forming a major mountain chain along the western United States, though they maintain their separate geologic identities throughout the rest of their extent.31