An "outcrop" is an exposure of bedrock or other deposits at the
surface of the earth. Outcrops do not cover the majority of the
Earth's land surface. In most places the bedrock or superficial
deposits are covered by a mantle of soil and vegetation and cannot
be seen or examined closely. However, in places where the overlying
cover is removed through erosion, the rock may be exposed, or crop
out. This is certainly such an area. Outcrops allow direct
observation and sampling of the rock on-site for geologic analysis
and creating geologic maps. On site measurements are critical for
proper analysis of geological history and outcrops are therefore
extremely important for understanding earth history. Outcrops are
also critically important for understanding fossil assemblages,
paleo-environment, and evolution as they provide a record of
relative changes within geologic strata. Outcrops can therefore be
considered a fundamental element of geologic science.
Nova Scotia's gypsum and anhydrite (anhydrite is gypsum without
the water) deposits are among the largest workable deposits in
Canada. Nova Scotia is the most productive gypsum mining region in
the world. Gypsum outcrops throughout the whole of the northern
half of the Province's mainland, and Cape Breton is flush with
gypsum and anhydrite. Areas in Nova Scotia underlain by gypsum
often display a very rough terrain, having many pits and mounds.
This karst topography is common even when the rocks themselves
cannot be seen at surface and is a good indication of the presence
of gypsum. Imagine this area with a layer of soil over it... it
would still be geographically distinctive! Almost all gypsum and
anhydrite occurrences in Nova Scotia are of the Carboniferous age
(approximately 290-350 million years old).
A Mohs scale test is used to test a minerals relative hardness. To
test the hardness of a piece of gypsum, hold the specimen firmly
and attempt to scratch it with the point of an object of known
hardness. Some examples of articles of known hardness are:
Talc - hardness 1
Fingernail - hardness 2.5
a penny - hardness 3
steel knife- hardness 5.5
Quartz - hardness 7
Diamond - hardness 10
Using this scale, you can determine the hardness of gypsum.
In order to log this
earthcache:
1. take a picture of you or
your GPSr at the apex of the outcrop and post it with your
log,
2. determine the hardness of gypsum using a Mohs scale test,
and
3. estimate the mass of the outcrop upon which you are standing
(in cubic yards)
Please email me your answers to 2 and 3; don't post them in your
log.
