Breccia/Tuff Green-> Red
Breccia/Tuff Green-> Red
Many of the rock layers are composed of a breccia of volcanic fragments from earlier parts of the volcano, held together with a matrix of altered ash. The ash is slightly green, reflecting the small divalent iron content. However, when a crack permits hydrothermal oxidation, some of the divalent iron becomes trivalent, and turns from greenish to reddish.
MoapaPk
on Jan 22, 2008 2:33 pm
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