DirtCache EARTHCACHE

PLEASE READ THROUGH THE ENTIRE EARTHCACHE BEFORE
YOU DECIDE TO DO IT. I WILL NOT ALLOW CREDIT FOR THOSE
THAT DO NOT POST RESULTS. I DO NOT WANT TO BE IN THE
POSITION OF DELETING ANYONE'S LOG.

Here's a chance for everyone in the area to participate
in an "EARTHCACHE". If you haven't done an EarthCache, you
are missing out on an interesting aspect of Geocaching.
Go to: http://www.earthcache.org/ and check out the
details. There are several Earthcaches in this area
(one at Mt Tabor in Portland and another in Eugene/Springfield
area and hopefully several more as I get some time to work
up some good ones.

This Earthcache is different in that it does not involve
a 'spectacular' or 'unique' geologic formation but rather
the everyday DIRT that we see everywhere! It involves a
little more work than most but the results should be informative.

This one involves a little preparation but it may also turn
into a Science Project for children/young adults in school.
Earthcaches are supposed to be a 'Learning Experience' and I
truly believe this one is a learning experience!

You will need to gather together a couple of items:

A small scoop,
A (maybe 2 of them) straight-sided glass jar (the
taller and narrower the jar the better -- a tall olive
jar is perfect!),
A very small quantity of a dish soap,
Some water,
A ruler,
Pencil and paper or calculator for the Math!!

Once you have gathered together, or have access to, these items,
go to the Earthcache coordinates given above near Canby, Oregon,
and get enough of a soil sample to fill a little more than one half
of your straight-sided glass jar.

AT THE EARTHCACHE COORDINATES THERE IS A SIGN FOR A NURSERY,
THE OWNER OF THE LAND HAS GIVEN PERMISSION FOR EARTHCACHERS TO TAKE
A SAMPLE OF DIRT FROM ANYWHERE WITHIN TEN FEET OF THE SIGN.

THANK YOU KEN!

Place your soil sample in a paper or plastic bag and take it home.
Spread the soil sample out on a sterile sheet of paper, counter or
laboratory tray --- OK, a few sheets of newspaper will work just
great because this is an approximation and not a very carefully controlled
scientific experiment!!

Pick out the bigger pieces of plant matter, non-soil items (bottle
caps, paper, etc) and pieces of rock larger than an 1/16th inch.
Little clods of soil can be left in because they will break up and
distribute themselves later in the experiment. You could also 'filter'
or 'screen' the soil sample by shaking it through a small piece of
window screen. Once you have removed all the non-soil items (if we
were doing a complete soil sample analysis the non-trash items would
be excluded but all the 'geological'items would be part of the
classification either by weight, density or size), fill the
straight-sided glass jar approximately one half, or so, full.

Put in just a dab (that's a scientific measurement that is just
a bit more than "none" and somewhat less than a "little bit"!),
you really don't need much of the super expensive liquid surfactant
that you have procured from under the Kitchen Sink. Dishwashing
Soap is a 'liquid surfactant' in that it breaks down surface tension
and helps to separate particles that are bonded or stuck together.
Then pour in enough mildly warm water -- good old tap water is
just fine -- to fill the jar about 3/4 full. Screw on the lid
tightly and agitate the contents for awhile. That means "Shake"
for this experiment and 'awhile' means that you should shake it
until it looks like everything has been thoroughly wetted and mixed up.

The soil sample that you use could even be a very consolidated
piece and then you would have to let it soak overnight and the
shaking would be more forceful but the sample will break down enough
for our purposes. Now remove the lid carefully and very slowly fill
the jar to the top with tap water and let the soap bubbles overflow and go
into the sink. Decant (that means 'pour out') a very small amount of
the remaining water from the jar and replace the lid securely. Set
the jar on a window sill or some place that it can be left undisturbed
for a few days.

The experiment will already have started to give data at this point!
The first material to settle out will be sand, over the next few minutes
the silt will settle out but the clay will take a day or so (maybe even a week)
to completely settle. You will know when the 'action' is complete because
the water above the settled materials will become clearer (it is unlikely
that it will become totally clear because some of the clay will stay in
suspension for a very long time!)

Once the water is sort of 'clear', you are ready for the 'measurement
and calculation' phase of the Earthcache. To do that portion, follow
these steps:

1. With the ruler, measure the total height of the 'precipitate'
in the bottom of the jar. Precipitate is the settled dirt

2. In a good light you should be able to determine the 'horizons'
in the precipitate. The material on the bottom will be grainier (sandy)
and the next layer will be finer but probably slightly different in color.
And the top layer will have no discernable grain size - clay. Measure the
thickness of each layer.

3. Determine the percentage of each material in the three layers.
For example, if the 'Total Height' of the precipitate is 2 inches, the bottom
layer is 1 inch, the middle layer is ½ inch and the top layer is
½ inch -- the percentages will be: Bottom layer divided by Total Height
times 100% equals 1 inch divided by 2 inches times 100% equals 50%. Similarly,
the middle layer will equal 0.5 inches divided by 2 inches times 100% equals 25%
and the top layer will be the same percentage as the middle layer because in
this case the layers are of equal depth.

Print out the image given below and enter on the 'SAND' side of the
triangle at 50% and color the line that goes into the interior of the
triangle. Then on the 'SILT' side of the triangle at 25% do the same thing
and where they intersect in the inner portion of the triangle you will see
that the soil classification is "SANDY CLAY LOAM". You could also follow
the line into the triangle from the 'CLAY' side of the triangle and it will
intersect at the same point because:

'50% SAND' + 25% 'SILT' + 25% 'CLAY' = 100% DIRT

There are other ways to quantify DIRT and perhaps we will do others if
this Earthcache is successful.

Obviously to Farmers, and all of us, DIRT/SOIL is a very important commodity.
If the makeup of DIRT is almost all SAND it will drain very quickly and
moisture will not be available to the planted crop. Conversely, if the
DIRT is all CLAY water cannot drain because of the cohesion of the soil
particles and it is almost impenetrable to water and the crop will 'drown'.

Further this experiment explains why that in fast running mountain
streams there is only SAND or large mineral pieces -- pebbles, stones,
rocks and boulders. When the gradient of the stream/river decreases and
the water slows, SILT settles out as in the Willamette River Valley that
has historically flooded and deposited SILT on the flat valley bottoms.
Lastly, the muddy river that flows slowly is carrying the suspended CLAY
particles until the flow is slow enough that they can no longer stay in
suspension. SAND and SILT only find their way far downstream
during heavy waterflows due to Spring snow melt or heavy precipitation.

DISCLAIMER:

FOR EARTHCACHE CREDIT: