Which types of magma are typically found in the Cascade Range of North America?

• A. Mafic only
• B. Felsic only
• C. Mixed mafic and felsic
• D. Intermediate only

Answer: (C)

The Cascade Range is characterized by a complex interplay of volcanic activity, which results in the formation of a variety of magma types. The correct answer indicates that both mafic and felsic magmas are present, making it a mix of the two.

In the context of volcanic activity within the Cascade Range, this region primarily features subduction-related volcanism, where an oceanic plate is being thrust beneath a continental plate. This process contributes to the generation of intermediate magma, which has compositions between mafic (basaltic) and felsic (rhyolitic) magmas. As a result, we see a spectrum of volcanic rock types, including andesites (intermediate) and rhyolites (felsic), along with some basalts (mafic).

The mixing of different magma types can lead to the presence of various minerals and volcanic rock compositions in the region. Thus, the presence of mixed mafic and felsic magmas reflects the geological processes occurring in the Cascade Range, making this the correct choice.