PART I.
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MOUNT MAZAMA.
LAVAS OF MOUNT MAZAMA.a
DACITES.
GROUSE HILL DACITE FLOW.
Possibly of about the same
relative age is the Grouse Hill flow, which crosses the crest a short distance
northeast of Llao Rock. On the inner slope the layer of pumice beneath the great
flow of Llao Rock overlaps the Grouse Hill flow, showing that the Grouse Hill
flow is older than the Llao Rock eruption. For this reason the two flows are
separated on the map. At the south base of Grouse Hill the dacite (107) is
regularly banded, and on the hill next northeast of Llao Rock it (108) is
spherulitic. This flow has been much eroded, and has a more ancient look than
other flows of this portion of the rim.
