Consider the 3 basic types of rock, i.e., igneous, sedimentary, and metamorphic.
When liquid rock, called magma, cools and turns solid through an exothermic process, it becomes a crystalline solid called igneous rock.
When inorganic material such as stones, sand, and minerals, possibly mixed with organic material, sinks to the bottom of water or is otherwise subject to lithification through (re)Crystalization, Compaction, and/or Cementation, it becomes a layered solid called sedimentary rock.
When either igneous or sedimentary rock has a drastic change in environment, e.g., being buried deep enough to raise temperature and pressure, it can change form into metamorphic rock.
The white rock we see here which is sometimes used as a building material, is limestone. This is a sedimentary rock formed from deposits of Calcium Carbonate (CaCO3). CaCO3 typically appears as calcite in fresh (often shallow & warm) water. When found in the the ocean, it typically appears as argonite.
Over a century ago, wagons passing through this low-water crossing left wheel ruts in the mud which eventually dehydrated and lithified into the permanently preserved evidence in stone we see here today. One particular traveler seemed to sink a little deeper than the others leaving a pretty impressive trail!
To be allowed credit for visiting this Earthcache, e-mail answers to the following questions:
from your visit ...
Q1) Were you able to stand in the wagon ruts left in stone? Why might you not be able to?
We have named the natural flow that led to these formations Brushy Creek and the unnatural flow, or flow of man, Chisholm Trail.
from the Earthcache text ...
Q2) Name some qualities of limestone that allowed for these marks to be naturally preserved.
from http://www.waymarking.com/waymarks/WM8R42_Brushy_Creek_Crossing_at_Round_Rock_Chisholm_Trail_Round_Rock_TX ...
Q3) What act was performed by man to unnaturally preserve some marks?
from additional reading material ...
Q4) What Greek word does lithification come from and what does that Greek word mean?
Q5) What form of lithification is specific to organic material?
Q6) Which of "the 3 C's" of the lithification process occurs primarily below the water table and is continuous in the groundwater zone?
Q7) Which of "the 3 C's" of the lithification process causes sediment to harden under self-weight?
Q8) Which of "the 3 C's" of the lithification process strengthens the material by locking particles together?
Q9) Based on what you know about lithification, hypothesize as to which 'C' was mostly responsible for this formation and which was least responsible.
As always, no couch potato caching, i.e., you have to actually visit the location, not just cleverly answer questions correctly without leaving the comforts of your home. Here is some additional reading material that you may find of interest, or even helpful in answering these questions.
http://www.austinexplorer.com/Locations/ShowLocation.aspx?LocationID=1968
http://itc.gsw.edu/faculty/bcarter/physgeol/sedrx/lith.htm
https://en.wikipedia.org/wiki/Lithification
https://en.wikipedia.org/wiki/Compaction_%28geology%29
https://en.wikipedia.org/wiki/Cementation_%28geology%29
Congratulations to j2dad on FTF with runner up going to Tigress & Waterweasel.