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| | Glaciers of California: CHAPTER FOUR |
 | | In the 1870s the origin of the valley became the subject of a dispute, sometimes bitter, known as the "Yosemite Problem" or the "Yosemite Controversy." At first, debate centered upon the competing roles of faulting, advocated by Josiah D. Whitney, and glacial erosion, advocated by John Muir. |
 | | The last Yosemite Glacier, of Tioga age, was not as large as that of at least one earlier glaciation and did not erode to bedrock. |
 | | Retreat of this glacier probably left waterfalls and a large, deep, lake that became in-filled with river-transported sediment, burying the lower part of the U-shaped glacial valley. |
| www.ucpress.edu /books/pages/8119/8119.ch04.html (6449 words) |
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