Why is Pennsylvania Unique?
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A view of Pennsylvania from the air offers
an opportunity to see stunning topography, geologic formations,
and the diversity of natural and biological resources that comprise
our Commonwealth. The mountains, ridges, and plateaus form the basis
for varied wildlife habitats, fertile ground for agriculture, ancient
winding paths carved by rivers and streams, the development of communities,
past and present, and vast forested areas that are uniquely Pennsylvania. Nowhere is the landscape more dramatic than
in the Ridge and Valley province, one of six physiographic provinces
that are represented in Pennsylvania. The Ridge and Valley physiographic
province sweeps diagonally across the state, forming the backbone
of the Appalachians, which begin in the Hudson Valley of New York
and extend south to Alabama. The Ridge and Valley, as a whole, gracefully
curves across the state from above Scranton in the northeast, then
south and west toward Maryland and West Virginia. Viewed from the
ground, the corduroy ridges, almost uniform in elevation, extend
apparently endlessly across the landscape. From the air, the true
character of the Ridge and Valley emerges. It is from this viewpoint
that the complex mosaic of patterns can be best appreciated. The
patterns appear as a series of maze-like folds and long sinuous
ridges separated by wide, flat-bottomed valleys. Invariably, the
steep ridges are forested, while the more hospitable terrain in
the valleys has served to concentrate agriculture and other human
development. The topography of the Ridge and Valley has a direct
effect on the climate—wind, precipitation, and temperature—of
the area as well. The ridges tend to suffer heavier precipitation
and more extreme variation in temperatures than the valleys. In
addition, the prevailing direction of the wind—usually from
the northwest, bounces off the ridges, causing the diverse types
of air currents that make soaring possible. The dramatic physical landscape is the result
of tectonic events such as earthquakes and mountain uplifting, as
well as millions of years of erosion. A type of tectonic event known
as an orogeny occurs when continental plates collide. The Allegheny
Orogeny, which took place approximately 250-300 million years ago,
resulted in the creation of the current Ridge and Valley. The process
of erosion, which is the effect of wind, water, and ice over time,
has sculpted and shaped the landscape of the Ridge and Valley into
what we see today. The combination of these elements—topography,
geology, and climate make Pennsylvania an ideal soaring environment
for birds and people alike. |
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 A regional view of the Ridge and Valley-From Pennsylvania through Tennessee.
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