A quick look at wikipedia tells us
that concretions occur where a space between sedimentary layers of
sedimentary strata that have already been deposited. They usually
form early in the burial history of the sediment, before the rest
of the sediment is hardened into rock. This concretionary cement
often makes the concretion harder and more resistant to weathering
than the host stratum.
There are some very dramatic examples of concretions around the
world. Some are dramatic by virtue of the density of their
occurance. (above left: "Rock City", North
Dakota ) Others are dramatic because of their complete
exposure. (above right:
hoodoo in Montana ) Others for their near perfect spherical
shape (below from left to right: Pop Rocks from Kansas, button rock
from Schoharie, NY and hematite spheres) or the brilliance of the
mineral deposits inside (geodes).
At these coordinates, we have two clusters of concretions,
visible on either side of the Conservation Trail / Finger Lakes
Trail just south of the trailhead at Getman Road. Some of these
concreations have a cracked/divided appearance that makes them look
like turtle shells. This is common enough that folks often mistake
concretions for fossils. Sometimes there are fossils involved, in
the center of the concretion for example, but the cracked surface
has its own explanation.
To claim this Earthcache:
1. Visit this site and look carefully at the each group of
concretions. It might help to take a picture for future reference.
Take note of how many concretions are in each group.
2. Review the related wikipedia website and formulate a
hypothesis that explains how these concretions are formed.
3.Explain the circumstances that create a cracked/divided
surface.
4. Email cache owner the total number of concretions and your
hypothesis of their formation and their cracked surface. (Hint: the
answer does not total thirteen... the title is a spin on the Native
American creation story "Thirteen Moons on Turles Back")
5. Log your visit and post pictures if you care to.
Conservation Note: Land owner was very explicit when giving
permission, that he would be very unhappy if visitors decided to
carry away his rocks or break peices off as souveniers. This land
owner also allows hikers to cross his property as part of the
Conservation Trail (continuous trail from Niagara Falls to the
Pennsylvania border in Allegany County). If he concludes that his
wishes (and property rights) are not being respected, the
consequences could be devastating to the hiking community (of which
I am one), so please don't give him cause to revoke his permissions
- leave everything as you find it.
Other references:
geology.about.com