Banded Skagit gneiss with cross-cutting dike of younger granite orthogneiss. Orthogneiss of at least two different ages makes up much of the Skagit Gneiss Complex. Some magma intruded while rocks of the Metamorphic Core Domain were being squeezed and probably folded. While the magma crystallized or soon thereafter, the squeezing (or flattening) aligned the minerals and the rock became foliated orthogneiss. Twenty million years or so later, much of the squeezing had ceased. When new magma invaded, the newly crystallized granitic rocks developed much less foliation than their predecessors.

Transferred from en.wikipedia to Commons by Maksim.

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From: http://www2.nature.nps.gov/geology/usgsnps/noca/sb9migma.html

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• (del) (cur) 23:53, 14 November 2004 . . en:User:Vsmith Vsmith ( en:User_talk:Vsmith Talk) . . 217x324 (39818 bytes) (Banded Skagit gneiss)