Godfrey Glen
5. Ignimbrite of the climactic eruption (unit cf) at Godfrey Glen (left center) on Munson Creek where it meets Annie Creek (below photograph), viewed from turnout on Highway 62. Deposit (~100 m thick) is compositionally zoned: juvenile blocks are uniform rhyodacite pumice in lower part, andesitic and gabbroic scoria in upper part, with a mixed zone in between. Color reflects emplacement temperature and compositional zonation of particulate matrix; stratigraphically higher and hotter material is dark gray. Thin, light-colored layer at top is the pyroclastic-flow deposit where it has been bleached by fumarolic alteration beneath a 1- to 2-m-thick layer of fine ash. Pinnacle landforms in middle portion of ignimbrite are relatively erosion resistant tuff indurated by precipitation of silica and other minerals in pore spaces near gas-escape fractures and chimneys during cooling. High points on skyline are Garfield (left) and Applegate (right) Peaks on south caldera rim 6 km north-northeast of photographer.
Photograph by Charles R. Bacon.