Mount Jefferson may form part of a long-lasting intracrustal melting and magma storage area that encompasses an area of , where relatively little mafic eruptive activity has occurred. The melting of the metamorphic rocks amphibolite and at deeper strata, granulite, have both produced intermediate and silicic lavas at Jefferson. The strip may still be active, as monogenetic vents near Jefferson have produced basaltic andesite since the last glacial period. Jefferson — with Mount Hood, the Three Sisters-Broken Top area, and Crater Lake — represents one of four volcanic centers responsible for much of the Oregon Cascades' Quaternary andesite, dacite, and rhyolite deposits. Some of this andesite and dacite occurs in vents that underlie the Jefferson vicinity, which also erupted during the Quaternary. Quaternary volcanic production rates in the Cascade Range from Jefferson to Crater Lake have averaged per mile of arc length per million years.