Geology Reference
In-Depth Information
Cave after the Floyd Officer family which homesteaded
here, the cave is one of the largest developed in non
karst terrain in North America. The cave was formed
by an unusual subsurface process where tunnels, sinks,
natural bridges, hills, and valleys are eroded in soft
clays and silts instead of in limestone. Caves of this
type can develop quickly as a result of a major storm,
when rushing water scours steep gullies or sometimes
causes the entire roof of the subterranean cave to
collapse. In the case of Officer's Cave, large, broken
blocks of the John Day Formation, fallen and tipped in
all directions, are flushed out by underground streams.
The John Day Formation is particularly susceptible to
erosion because of its soft, poorly consolidated nature,
a characteristic frequently leading to landslides and
rockslides.
Officer's Cave is a maze of various levels
originally over 700 feet long when first explored by
geologists in 1914. The cave has increased in volume 5
to 10 times since then and when examined in 1975 was
Officers Cave is developed in the John Day Forma-
tion where soft clays have been washed out by
subterranean streams.
Steins Pillar in Crook County is an erosional remnant of volcanic ash-flow tuffs of the Clarno and John
Day formations (photo courtesy of Oregon State Highway Department).
