With the winter solstice upon us, I have been looking back when the days were longer and warmer. On an excursion to the east side of Eagle Lake provides for an interesting setting of the geology of Eagle Lake. This, of course, I am indebted to Michael Clynne of U.S.G.S who enlightened me.
There is some spill over the Sierra Nevada at Eagle Lake. Gallatin Peak is a perfect example. Unknown to many, is fact if one could remove the Brockman Flat Lava flow, underneath one would find granite composition. In addition, Brockman Flat Lava flow extends to the east side of Eagle Lake at Bly Tunnel. When this occurred it blocked the flow of Pine Creek from leaving the basin. The tailing piles of Bly Tunnel offer the evidence. At the inlet, the tailings are of granite composition.
At the next tailing pile has changed becoming more basalt in nature and fitting in the Cascade element. This is especially evident at the tailing pile at the outlet, which even consist of some volcanic cinder, unfortunately, that particular tailings I do not have a color photograph to highlight it.