Temporary Places

Gorge 9
Description | This outcrop location marks the topmost layers in the Bishop Tuff. In this section, the tuff was altered by vapor-phase transport of hot gases through the tuff. The vapor percolates out of the porous and permeable top of the tuff, leading to vapor-phase crystallization. This part of the Bishop Tuff is pink, vuggy, white and sugary in appearance. The pumice is eaten away by corrosive gas streaming through from fumarolic activity. At the very top, some intact pumice remains, but is recrystallized. In this general area, you can find Herkimer quartz that formed through recrystallization in the vesicles. The approximate elevation here is 6015 feet, or 1833 meters.
Photos

Gorge 1
Description | At this location, we are approximately 18 meters below the Gorge 9 top location. The degree of welding at this location is slight and variable. Mostly the pumices have not deformed much and remain intact. A few fiamme are observed here and there. Elevation at this location is about 5943 fee and the difference in elevation with the top of the plateau is about 180 feet.
Photos

Gorge 2
Description | At this location, we are approximately 20 meters deep into the tuff, relative to the top Gorge 9 location. At this location, the degree of welding increases by a small amount and fiamme (squashed and heated pumices) are observed. The outcrop pattern following the road bed here allows for a slightly higher degree of welding and compaction to be observed, compared with the Gorge 1 stop which is just about 2 meters higher in elevation. Elevation here is approximately is 5936 feet and the difference in elevation with the top of the plateau locally is about 200 feet.
Photos

Description | Fiamme are regularly observed here and the degree of welding is about the same as the prior location at Gorge 2. The elevation is approximately the same as the Gorge 2 outcorp location. Elevation is approximately 5942 feet and the difference in elevation with the top of the plateau locally is about 202 feet.

Description | In this location, the road starts cutting into a more densely welded section of the Bishop Tuff. Photos show many fiamme and what appears to be a greater degree of welding through flatter fiamme and more fiamme. Accidental rock fragments (lithics) that are not deformed are also shown here. This rock fragment appears to be a chunk of granite from the Sierran basement rocks. Notice that some of the fiamme are very deformed and wispy looking. Some fiamme look very glassy (just black), while others show large crystals (white crystals) indicating they are starting to recrystallize due to prolonged heating. This process is called "devitrification". Elevation is about 5944 feet. The difference in elevation at this location with the top of the plateau is about 186 feet.

Description | At this location, you can see examples of relatively glassy to partially devitrified fiamme. The two photos show examples of those textures. Notice that the matrix surrounding the fiamme remains fairly crystal-poor Elevation here is approximately 5930 feet. The difference in elevation at this location with the top of the plateau is about 219 feet.

Gorge 6 and 7
Description | At the Gorge 6 location, you can see extensive devitrification textures and fiamme. The deposits here are visually more crystal-rich. It is likely that the very slow cooling deep within the ignimbrite allowed the tuff to stay hot enough long enough to promote robust re-crystallization.
Description | At the adjacent Gorge 7 location, you can see horizontal gas escape structures and buff pink colored partings with lithophysae. The elevation at this location is approximately 5903 feet. The difference in elevation with the top of the plateau locally is approximately 240 feet.

Description | At this elevation, we are getting near the lower layers towards the base of the tuff. Here, the matrix and fiamme all look quite crystalline and devitrified. The interior of the tuff deposits had remained hotter longer than any other section. The glass in the matrix and pumice (fiamme) have likely re-crystallized extensively because of this. The elevation at this location is approximately 5856 feet. The difference in elevation between this location and the top of the plateau is approximately 342 feet.