Johnson Peak 2013


Interesting Facts & Highlights


Johnson peak has the distinction of being the youngest granodirite of the Tuolumne Intrusive Suite. Four bodies of plutonic rock starting with the Kuna Crest (91 million), including Half Dome and Cathedral Peak (86 million) and finishing with the Johnson Granite Porphyry which is estimated under 86 million years. Radiometric tests have not been carried out in order for an accurate determination. The general characteristic of this rock shows as a finer and lighter grain than surrounding areas, which requires that partially crystallized magna cools relatively quick, indicating that a sudden release of pressure, as coming from volcanic eruptions, would be a probable cause. A massive caldera high above the current elevation most likely existed, with the volcanic deposits and underlying rock eroded away over the years to produce our current day conditions.

Elevation & GPS



2013 Mz, Gn summit

The peak itself was named in the 1890s by R.B. Marshall USGS in recognition of a survey party teamster who had been a useful guide, having been with Professor Davidson's party at Mount Conness earlier.


Sourced from The Geologic Story of Yosemite National Park (1987) by N. King Huber

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