Get Down & Dirty EarthCache
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This Earthcache will take you to an area with flat to gently
rolling landscape. Common within Dekalb County, and extends
northwest to the South Bend area. A gift from the glaciers, and
known as the Dekalb Lowlands. You may say, “There's nothing
here”. The wealth lies beneath your feet! Be sure to bring
along a container of water, paper towels, and a camera. You'll
probably want all of them to log this cache.
What's the difference between soil and dirt?
Dirt is what you find under your fingernails. Soil is what you find
under your feet. Think of soil as a thin living skin that covers
the land. It goes down into the ground just a short way. Even the
most fertile topsoil is only a foot or two deep. Soil is more than
rock particles. It includes all the living things and the materials
they make or change.
Soils form through processes acting upon deposits of plants and
geologic materials. The characteristics of a soil at any given
point are determined by:
( a ) the physical and mineralogical composition of the
parent material
( b ) the climate under which the soil
formed
( c ) the plant and animal life on and in the
soil
( d ) the topography, or general configuration of the land's
surface
( e ) the length of time the soil forming factors have acted
upon the parent material
Let's take an elevator ride from the surface
to the bedrock below. We'll pass several distinct layers as we go.
Together, these layers form the soil profile. Going
down!
Ground level: Plants grow
and animals live here. Decomposers recycle dead plants and animals
into humus.
Topsoil: This is
sometimes called the organic layer. Higher concentrations of
organics and microorganisms are found here. A thick cover of plants
can keep the soil cool and keep it from drying
out.
Subsoil: This is a
mix of mineral particles and some humus near the top. Subsoil is
very low in organic matter compared to the topsoil. This is the
layer where most of the soil's nutrients are found. Deep root
plants come here looking for water. Clays and minerals released up
above often stick here as water drains
down.
Weathered parent material:
*There's no organic matter here at
all. We're out of reach of all living and dead organisms down here.
It's all rock particles, full of minerals. This horizon can be very
deep. In areas of Dekalb County, it extends 300-500 feet below the
surface.
Bedrock: We finally
found rock! This Devonian bedrock formed long before the soil above
it. It will wait here until erosion, or a catastrophic geologic
event exposes it to the surface. Then some of it will be weathered
to become the next batch of parent material. The soil making
process will start all over again.
*Parent material in this
area was deposited primarily by glacial movements that covered the
northern 2/3 of Indiana. The most recent, being the Wisconsin
glacier. Varying rates of ice melt caused eroded sediment to
“drop out” of retreating, melting glaciers. This
“glacial till” formed deposits called moraines and
drumlins. Glacial till consists of unstratified (unlayered) and
unsorted glacial deposits, some in the size of huge boulders. Melt
waters flowing upon, under, within, or at the margin of glaciers
accumulated deposits known as outwash plains, kettles, kames, and
eskers. These are the topographical features most easily recognized
in the area.
Organics, chemicals, and other components aside, there are
only three basic units, or classes, of soil. Surprisingly these are
not based on the materials, but on the
size of particles.
Sand:The major
mineral in sand is quartz. 0.05 – 2.0 mm in size. Quartz is
very resistant to weathering; therefore sand grains are larger in
diameter compared to silt and clay
particles.
Silt: Silt
contains silicate materials like sand but the diameter of silt
particles is smaller, 0.05 - 0.002 mm, and so the pore space
between silt particles are smaller.
Clay:Silicates,
mica, iron, and aluminum hydrous-oxide minerals are found in clay.
Clay particles are 0.002 mm in diameter or smaller, so the pore
spaces between clay particles are very
small.
Ideal soil, for most agriculture, has some
of each type---sand to help with drainage, silt to boost mineral
richness, and clay to trap moisture and keep nutrients from washing
away. Too much clay in soil means that there are scarcely any air
gaps, which can suffocate plant roots and beneficial microbes
alike, and it also makes for poor drainage. Excessively sandy soils
can drain too well, leaving plants vulnerable to drought without
frequent watering.
The best soils contain about 10%-20% clay,
and roughly equal proportions of silt and sand. A soil with these
optimal proportions is called loam. A
good loam
also contains plenty of organic matter (as much as 5%- 10%) to
supply nutrients.
It's common to find several types of soil within
a small area, such as a single field. This can be largely due to
the immediate topography and erosion.
Now it's time to get down and get dirty.
(This is an old, but quick way to check the basic soil type.) At
the coordinates, grab a handfull of “dirt”. If it's not
already wet, add just enough water so you can knead it. Try and
make the following shapes. The shape you get most easily will tell
you what type of soil you have. (Rolling it between your palms
works best.)
The final shape you get is the soil texture,
for example, if a worm shape can be made but it breaks if bent, it
is a loam.
To log your find, post a photo of your
pre-test sample at the site(optional), and email me
the results of your soil test. Please don't mention the type of
soil in your log.
Additional Hints
(Decrypt)
[Dig down an inch or so to get a sample not directly subjected to sun, wind & precipitation. Remove pebbles & large vegetative matter. Private property, with permissions.]
Treasures
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