Geology of Appleton
Ridge
Ever wish to visit Africa, but realized it was just another unattainable
fantasy? Ever want that
fantasy to come true? Well, you can visit Africa without ever setting
a foot outside the state of
Maine.
The town of Appleton contains a geological oddity where many of the
rock formations are of
African nature. This is so because long ago, when the North American
tectonic plate was
connected to the African tectonic plate, Maine and Africa were touching
eachother. It was here
where the actual fault zone was. When the plates pulled apart from
eachother, a large chunk of
Africa ripped off and was left attached to Maine. One side of the
fault is composed of rocks of
African descent, the other side has rocks of Maine descent, and the
actual fault itself is
composed of both in fairly equal quantities. Let's have a look at
some of those African rock
formations.
This is what the typical rocky outcrop at
Appleton Ridge looks like. While rocks of all
types occur all over the world, some types
are more prevalent in certain areas. This
type of rock formation is most prevalent on
the north-western portions of the African
tectonic plate. You can see that it is a high-
grade metamorphic rock composed of deep
marine shale. When this rock was formed, it
was underwater far off the coast. You can
see the effects of pressure over long periods
of time with the way the rock sways to and
fro. The small lines of minerals and different
depositions indicate high pressure and heat,
too.
This particular picture
illustrates well the
porphyroblasts that are present
in the schist. The crystals
of varying size
are made up
of the mineral staurolite.
It crystalilzed under high
heat and pressure and
was trapped inside the
shale. Its also much
harder than the
surrounding rock. You
can tell this because the
staurolite crystals
protrude from the rock they're
embedded in, because over a long
period of time the schist
has been eaten away at
by weathering of all
sorts; chemical,
phyisical, and glacial.
The second picture in
this set illustrates this
point very well. It's quite
easy to see the pitting of
the rock.
Its not just shale that is at
this site. There are other
rock types, as well. Take
for example this piece of
schist. It too has staurolite
crystals embedded in it. Its
here because it is formed
under similar conditions to
the shale in the area.
Notice the shiny,
multi-colored surfaces of
the rock. That is due to mica formed from the
metallic elements that are
part of the rock such as
iron and aluminum. The
second picture in this set
shows the quartz bodies
that are present in the
surrounding shale. Some
places the quartz is fairly
thick and easily identifiable
while in others, due to
thousands of years of high
heat, pressure and stress,
the quartz has been
extruded and squeezed to
mere fractions of an inch.
Appleton Ridge is an area of geological interest to many people. For
geologists, it is an area to be studied and learned from. For others,
an
area to relax and recreate. For all, an opportunity to experience
the
exotic while never leaving home.