What You Need and
“Things To Be Aware Of”
You will need a metre rule/stick and a friend may be useful. Be
careful of passing cars.
Background
Most soils have horizontal layers known as soil horizons.
These differ in their physical, chemical and organic composition.
Several geological processes affect the formation of soil horizons.
The weathering of rock and succession of plants to form the
particles of sand, clay, silt and organic matter is discussed in
the earthcache "Getting the Good Dirt." Once the soil has formed
eluviation (the downward transport of fine particles (eg clay) by
rainfall can occur. This may change the layer that this material is
leached from and the layer that it is deposited into.
They are absent in soils which have not had enough time to form
horizons (eg sand, swamp, glacial moraine, ash, river gravel) and
where there has been significant human disturbance (eg landscaping,
excavation).
A vertical column of soil showing these soil horizons is known
as a soil profile. Soil scientists usually obtain these by using an
auger or the good old fashioned spade. Road cuttings provide an
excellent opportunity for viewing soil profiles without the
sweat!
A Typical Soil Profile: Thanks US Dept of
Agriculture!
O) Organic matter: Litter layer of plant residues in relatively
undecomposed form.
A) Surface soil: Layer of mineral soil with most organic matter
accumulation and soil life. This layer eluviates (is depleted of)
iron, clay, aluminum, organic compounds, and other soluble
constituents. The layer E may be found below this when eluviation
is pronounced.
B) Subsoil: This layer accumulates iron, clay, aluminum and
organic compounds.
C) Parent rock: Layer of big unbroken rocks. Note: these are the
common horizons, refer to sources for other horizons.
Logging
Requirements
0. Preface any email with GC28HP Broadening Your Horizons
in the subject line and title and clearly note the question number
and answer. You don't need to wait for a confirmation email to log
but you might be asked for more info if your answers are slim.
1. Using the information above identify which soil horizons are
present at GZ. Place your metre rule vertically (at base of the
manuka tree opposite the survey marker) and use this as a guide for
measuring the thickness of each horizon. Note: running a tape
measure over the horizons won't work as this introduces a
horizontal component due to the slope. Don't be afraid of the >
sign if you can't see all of a layer! Email the horizons present
and their thickness.
2. What is the name given for the process where fine particles
such as clay are transported downwards through horizons by
rainfall? Email this.
Key
Sources
Wikipedia article on soil
horizons
Wiley Interscience: animation on soil horizons
2010 Stegan’s
EarthCache Masters Programme
Since it is not very feasible for many NZers to easily get more
than two states for the earthcache.org masters programme and
therefore not get past Bronze I’m running my own one on a
number of Earthcaches that I plan to release this year (all things
being equal) with the following points system:
5 points: First to find
3 points: 2nd to find
1 point: Logging a find
1-5 points: Special bonus questions.
Shared points for joint finds.
At the end of 2010, I’ll issue certificates for 1st, 2nd
and 3rd and the first place getter will be awarded a geocoin. If I
feel richer and/or it looks like this is popular I’ll upgrade
the prizes.
Updated information and Leaderboard at: Stegan’s
Earthcache Programme