Shale-Layers of Time and History
This Earthcache is located in the Shawnee State Forest in
southern Ohio. Please be respectful of the environment and the
Park rules and regulations.
Removal of any natural materials, plants, artifacts, etc. is
prohibited. CITO is still ok and encouraged.
General Forest Rules
- Shawnee State Forest is open to visitors between the hours of 6
a.m. and 11 p.m. daily. Legal campers, hunters and anglers may be
present during other hours.
- Operation of motor vehicles is restricted to roads provided for
such travel. The speed limit on state forest roads is 30 mph unless
otherwise posted. Vehicles may not be parked where traffic or
access to division service roads or trails will be obstructed.
- Horses may be ridden only along forest roads or on designated
bridle trails.
- Swimming and motorized boats, except with electric motors, are
prohibited in state forest lakes.
- Fires are not permitted except in grills or fire rings provided
or in portable stoves. Fires must be attended at all times.
- Litter must be disposed of in receptacles provided.
- Camping is permitted only in areas provided and designated for
such use.
- Public display or consumption of any alcoholic beverage is
prohibited.
- Disturbance, defacement or destruction of any property,
material, natural feature or vegetation is prohibited. Berries,
nuts and mushrooms may be gathered and removed except from tree
seed orchards or posted areas.
The shale seen at this location has been exposed by water
erosion from the creek as it has cut down through the hillside.
Gravity, rain, and wind are also factors in this process as the
thinly flaked rocks break off easily and fall or slide
downward.
Shale is a sedimentary rock that has been laid down millions of
years ago as mud or clay in thin layers. It is composed mostly of
quartz and other minerals found in clay. If a particular type of
rock is classified as sedimentary, it only means that it was once
fine particles (usually) that were suspended in water, settled to
the bottom to form a new layer, and has been compressed over time
into a solid mass. Think of taking powdered Plaster of Paris and
mixing it with water. When the water is removed by evaporation, the
fine granular material is now a large chunk. Sedimentary rock is
similar but has been fused together by pressure and time instead of
just evaporation.
The creek bed at this location appears at first to be composed
of a different substance. It is eroding quickly downward as the
flowing water dissolves the rock. If you walk in the creek bed it
will crack and flake off small pieces, thus causing the exposed
rock to erode even faster. If you walk along the banks upstream a
short distance, you will notice that the rock type has changed to a
different kind of sedimentary material. Downstream is also
different, however there is a great amount of shale that has been
moved by flowing water from this location.
Clay itself is composed of very fine particles of quartz and
other materials that exhibit plastic (able to change shape by
pressure) qualities when mixed with water. The more water content
for a given amount of clay, the softer it becomes. On the other
hand, as water is removed, it becomes more rigid and when shaped
and heated it can be used as pottery or art.
The process of forming shale has been through downward pressure
from the weight of the layers above. As the layers are “squeezed”
by the pressure, the water is forced out and energy is released in
the form of heat. Over long periods of geologic time this heat and
pressure has formed the shale we see today. One of the standing
principles of geology is that if left alone (not over-turned etc.)
the oldest layers of sedimentary material is on the bottom, and the
youngest are on the top.
SHALES are sometimes misidentified as slate. Slate is formed
when shale is transformed by pressure, heat, and time into a
different kind of material. This heat and pressure may cause the
recrystalization of the parent rock, effectively making a different
rock. Once changed it is no longer sedimentary, but now classified
as metamorphic rock. While shale is thin and found mostly in small
pieces, slate is much thicker and can be used for chalkboards (for
those of us old enough to remember), billiard tables, and walkways
to list a few.
To get credit for this EarthCache email the answers to the
following questions to me and post a picture of you and your GPSr,
with the creek bed or the shale “wall” in the background. Logs with
no pictures will be deleted
Questions:
1. What is the width of the creek bed at this location?
2. What type of rock is shale, sedimentary, igneous, or
metamorphic?
3. What is the elevation at this site?
Credits and Ammosuperman EarthCaches:
This EarthCache was created by a team of two Platinum EarthCache
Masters, Ammosuperman EarthCaches are a collaborative effort. We
have used resources such as the Internet and magazine articles as
well as personal experience in visiting the sites, as research
tools in its construction. Our goal is to learn more about our
planet and to pass along what we have learned to others having
similar interests. We hope you enjoy the experience.
Special thanks to Tim Wilson and the Shawnee State Forest for
allowing this EarthCache.
