The Geology of Crater Lake National Park, Oregon With a reconnaissance of the Cascade Range southward to Mount Shasta by Howell Williams
The Climax: Culminating Explosions of Pumice and Scoria
The Main Pumice Fall
Lithology of the Main Pumice Fall
Next to be considered are the variations in the coarseness of the ejecta, the proportion of crystals to glass, and the amount of lithic detritus, that is, fragments of old lava, present among the deposits.
Fig. 17. Size distribution of samples of pumice fall. Distances measured from center of the caldera.
Sorting of the pumice by size. Moore5 rendered a valuable service in preparing sixty-one mechanical analyses of samples of the pumice fall, a few of which are reproduced here as figure 18. Many more separations were made during the present study, and some are included in figures 17, 19, 20, 21, and 22.