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merged. As waters retreated, the western edge of what is now Amer-
ica poked free, but through the majority of Montana, water covered
the land until it retreated further during the Paleogene period (about
66 million years ago).
I spoke with Greg Liggett, a paleontologist with the Montana Bureau
of Land Management, to get an idea of why the Pryor and Bighorn
mountains are so dramatically different from the Beartooth Mountains
a short distance away. He explained that around the time the waters
retreated, the Larimide Orogeny (the time period when mountains are
being pushed up) was occurring. While it was pushing the metamorphic
and igneous rock of the Rocky Mountains upward, it was also pushing
up the Madison Limestone formations. These mountains then turned
into one of the most magnificent caving systems in the country.
Greg explained, "One of the interesting aspects of limestone is
that it's very susceptible to cave formation. Since it's made from cal-
cium carbonate, it reacts with acids; rain naturally becomes slightly
acidic on its way down." Given enough years, immense caverns form.
A room full of stalagmites and stalactites.
Author Scott Sery points out the gypsum formation Pete's Mustache.
Fossilized coral
embedded in
the ceiling.
CUYLER HARVEY (3)
