Logging Requirements
1.What is special about this
rock?
2.Give an estimated height and an
estimate of the area of the rock
3.What is approximately the average
difference between most of the bands on the rock (In Inches)
4.Take a picture with the rock and
your team and/or GPSr at the rock.
This earthcache takes you to a park
called 'Ford Field' which is part of the Northville Parks and Rec
Department. Please only visit this park during the daylight, and be
respectful of the property. The questions are here to insure me
that you have indeed visited the site and have learned something
about Gneisses.
A Gneiss (Sounds like Nice) is a
fairly common and frequently seen type of rock formed by high-grade
regional metamorphic processes from pre-existing formations that
were originally igneous rocks. Gneissic rocks are usually medium to
coarse foliated and largely recrystallized and do not carry other
types of platy materials such as mica or chlorite. Gneisses that
are metamorphosed igneous rocks or their equivalent are termed
granite gneisses. Orthogneiss designates a gneiss derived from an
igneous rock. This particular rock is a weakly metamorphised
gneiss. It is a special rock because it is hasn't been fully
metamorphised but it is still a gneiss. These rocks can be massive
and can be spotted from their distinctive horizontal lineiation.
Gneiss resembles schist, except that the minerals are arranged into
bands. Sometimes it is difficult to tell the difference between
gneiss and a schist because some gneiss appears to have more mica
than it really does. This is especially true with mica-rich parting
planes. Gneisses also have a reputation to be confused with
granite. An illustration of the difference in texture between a
granite and a granite-gneiss. Granite-gneisses (B) have foliation,
indicating that they have been deformed after the original granite
(A) cooled. The gneisses have been around longer, meaning that it
has more opportunity to be “squeezed” by mountain
formation. This illustration shows the difference between a Granite
and a Granite-Gneiss. The Granite is (A) and the Granite-Gneiss,
like the rock that you will be examining for this cache is (B).
Congrats to The Atkinsons on the FTF!