Friday, July 9, 2010

As the soil turns.

Hello dear readers! I went on a quick trip to Swallow Falls State Park in Maryland.  Swimming in the waterfall was so much fun!  I took a few pictures as I thought about the difference between rocks and soil.

There are 5 factors that work together to form soil:
  1. Parent material - It can be mineral and/or organic (i.e. decomposing plants).
  2. Climate -  Different environmental factors (i.e. temperature and precipitation) affect chemical and physical weathering
  3. Living organisms - Among other things, they help organic matter biodegrade, and can mix soil layers/horizons into each other.  Their chemical reactions can cause chemical weathering.
  4. Topography - For example, valleys accumulate soil and water, hilltops shed them.  This affects the type of soil created. 
  5. Time - Neat factoid: sometimes a very chronologically old soil won't be very developed, and vice versa.
For more, there are quick explanations at NASA and the NRCS.

The Soil Science Society of America gives us a two part definition of soil. This is the first part: 
 "The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants."
Below, I'm sharing with you my pictorial exploration of a plant's contribution to soil development.

Plant pioneers.  This guy might trap tiny rock fragments or organic debris which will grow his soil pile.  To be honest though, erosion is high here.  It was on a slope.  This soil might not develop further.

These guys have a small part in a very big process.  I imagine their roots will help make this crack a little bigger, making it able to hold even more soil, allowing even bigger plants to grow here in the future.

Growing sideways out of a crack between two rock layers.  Not much opportunity for soil development here, but don't tell her!

This shrub (tree?) has chutzpah.  It looks like it is growing out of the rock.

It looks like these guys are the furthest along in helping to develop soil, but they still have a looooong way to go!  When these plants die, they will contribute organic matter to the soil for new plants.  

Even if these little bits of soil are chronological Methuselahs, environmental factors prevent them from developing horizons.  Mayhaps erosion rates are faster than the rate of soil development.  If so, the soil would be characterized as an Entisol.  Entisols are the youngest (meaning least developed) of the 12 soil orders. 

And let's end on a lithologic music note...


  1. Great post! It appealed to my intellect and senses.
    Simon and Garfunkel- the bomb!!