John Muir


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Glaciation of Lava regions

Many of the lavas are so soft as to crumble under glacial action or so [cut] by clvg [cleavage] planes as to give way & break up in very irregular forms leaving a rough surface wh soon parts with glacial marking by subsequent weathering. The extreme variability also of the lavas both in the resistance offered to ice action & in the method of their acquirements of form greatly increases the difficulty of reading glacial history inscribed upon them. Sufficient however is [clear] to determine the fact that almost the entire lava deposits of the Sierra [covering] half the range in thick blankets & obliterating the pre-volcanic [Sierra] landscapes by filling its valleys & burying its hills & ridges & mtns [mountains] is pre glacial in age & that the greatest & most


universal of the later floods of fire were outpoured just at the period of the obliteration of the ancient rivers. Also there are hard lavas still manifesting the polish scratching & [moutoned/montanced] forms of glaciers together with well [defined] [moraines] in some favored places. Notably at the head of Independence Lake showing that the crumbled hills & hollows of this region with their various lavas sculptured into all kinds of fantastic & picturesque forms remain to this day almost unchanged however great the changes of the preglac periods & nowhere are these changes more strikingly exhibited on the very summit of the range along the head of the Feather tributary. There seems to have been a great val now filled with

Date Original



Original journal dimensions: 10 x 17 cm.

Resource Identifier



Holt-Atherton Special Collections, University of the Pacific Library

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John Muir, journals, drawings, writings, travel, journaling, naturalist