Fall Quarry Run EarthCache
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The Rappahannock River moves through Fredericksburg from the Virginia Piedmont, dropping twenty-five feet over the distance of the mile you just walked to the site. This area of the River has a variety of geological gems that the Earthcacher can consider.
For instance, a discussion of the Fall Line is available at the Earthcache further East, and I invite you to check out the description of that Earthcache for a rundown of many aspects. Naturally, I don't want to duplicate the fine information discussed there.
Please insure that you take proper precautions on the trail during hunting seasons: 3 October-23 January and 9 April-14 May. Also, after your visit, consider checking out the trail information available at http://www.mtbproject.com/trail/7000676, which describes 11 miles of Quarry paths on the Rappahannock River Heritage Trail.
Keep in mind that at any time there might be markers on the trail closing its segments due to dangerous conditions and other potential issues. As a cacher/hiker, take whatever alternate routes you find available to properly circumvent the problems. If the main entrance signs indicate a closure, it's more than likely best to cooperate with the temporary condition.
Your location (at what is called Fall Quarry Run) offers additional views of the Northern region of the Rappahannock Falls and the rockbeds that have been affected by geological and environmental violence over millions of years.
You'll pass this entrance to the falls on your way upstream :
Some Technical information:
Hundreds of millions of years ago the Appalachian Province, Piedmont Province and Coastal Plain resulted from global upheaval (rock moving through the surface from underground, volcanic/metamorphic activity, high velocity rains and winds, etc.).
There are two significant conditions that occurred in the region at that time: (1) the Coastal Plain suffered both glacial and environmental change, and (2) the Appalachian Province's mountains were affected by various environmental factors.
Geologists have determined that glaciers North of your location (as far South as the SE point of Pennsylvania and Southern New Jersey) deformed, with the water resulting from the melting moving down what became the Delaware and Susquehanna Channels. The glacial activity had affects on the areas East of your location, including some Piedmont distributions that moved through this spot.
More applicable to Fall Quarry Run is what happened West of the Fall Line, from the entry point of the trail you traveled all the way West to your point of view (and further West).
The ancient mountains were pushed up throught the existing surface 300 million years ago. Rain and wind eroded the mountains, sending mud and sand along fresh waterways East toward the Ocean. During those events, especially over the past 150 million years, the erosion flattened the landscape West of the Fall Line to the current Appalachian mountain range, leaving the igneous remains (the bedrock) exposed on the flat Piedmont.
Today, we know the channels to the East as the Delaware and the Chesapeake (formed as Bays 3,000 years ago) and its tributary rivers (Susquehanna, Potomac, Rappahannock, and York). Very high seas back then also pushed organisms and sediment West off the Ocean, causing additional erosion and deposits (mainly limestone).
According to virginiaplaces.org, the waters flowing East and South carved new channels across the Piedmont and Coastal Plain through soft sediments and hard bedrock, carrying dissolved and suspended particles downstream to be deposited enroute to the mouth of the Bay at the Atlantic Ocean.
From the geologists:
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Potholes, in the geological sense, are caused by water erosion, weathering, wind or temperature changes. Smoothing is caused by similar environmental activity.
Water flow erodes the bedrock over time, creating potholes of varying shapes, depths, and sizes. In addition, the term "bio-weathering" was coined to describe the large affect organisms have on how the potholes are formed. The organisms involved are algae, bacteria, and fungi, collectively referred to as biofilm.
The biofilm interacts with minerals and weathers the rock. As a result, while the water erodes the rock, so do the organisms.
Temperature changes can also affect bedrock as water forms and remains in the potholes, freezes, melts, dries, and warms. That activity tends to break down the rock over time.
Our Focus:
The era we are considering for the purposes of the Earthcache is the Pleistocene. Pleistocene is defined as newest (most recent). Appropriately, it is the era immediately prior to our present geological period. The Pleistocene era spanned approximately 1.8 Million years, ending 11,700 years ago at the same time as the final glacial activity.
As you can imagine, hundreds of millions of years of erosion can have an enormous effect on the landscape.
Three of the interesting phenomena found here are:
(1) potholes, which are gaps, holes, and gouges found in, on, or within the rock;
(2) the large sizes of some of the rocks, and the lesser erosion of those stones; and
(3) the erosion's after effects on the rock - like relocation, polishing, smoothing, and forming of the rocks you can see evidence of here.
Additional information:
There is quite a bit of material available on the net regarding rock. For instance, you'd find that there are three major types of rocks:
(1) sedimentary - think settling minerals and organisms;
(2) igneous - usually volcanic; and
(3) metamorphic - sedimentary, igneous, and metamorphic continuing to change over time.
Have a seat on a rock near the coordinates.
The resultant rock you see before you is mostly igneous. Igneous rock types include granite, quartz, basalt, pumice, among others.
Note the two sets of large rocks directly in front of you half way across the river. During the Triassic era, 200 Million years ago, much larger rock was created by superheated magma and placed there as material moved from subterranean levels to the surface. Naturally, over 200 Million years, those large formations would have eroded considerably.
Consider what additional effects the winds and rains (and the biofilm) had on that pre-existing environment, as a deluge advancing at four or more times the force of a hurricane like Agnes cascaded through the area over hundreds of thousands of years.
Look a bit to the right closer to shore, where you'll find various rocks with pot holes evident (usually round with some water remaining in them). Then, a bit to the left, try to find what looks like a statue of Neptune rising with his back to you. These rock structures show not only potholes, but the smoothing effects of much erosion.
As you scan further left, you'll note a couple of rockbeds that show deep gouges - they are not layers, but appear to be wear marks by something like passing water. Those beds also portray the effects of smoothing. A final scan to the shore line on the left, you'll see other examples of the same - pockmarks - they are similar to impact craters; potholes (shallow to deep); gouges; and toward you one of the isolated water pockets that are secondarily formed by the overall effects on the region. Some of those isolated waters can be rather deep.
Consider doing a little bit more research to dig into the characteristics of all of the location's aspects. In addition, I also suggest you follow up your visit with some research into "Pangea" and the massive global movements of the time.
Questions:
(1) What do you believe created the pot holes? Swirling eddies, moving quartz sand, high speed water flow, wind, ice, or erosion?
(2) What form of weathering do you believe caused the smoothing and erosion of the rock?
(3) Do you believe that the potholes were created before they were moved to their present location by the Pleistocene glacial upheaval? How do you come to your conclusion?
In order to insure permanence of your smiley, take a moment and send your answers to the questions to the cache owners.
”GoingToPot” has earned (GSA) Geological Society of America's highest earthcache level:
Platimum Earthcache Level is awarded by Geo Society .org for visiting and logging 20 or more EarthCaches in 5 or more states/provinces/countries and have created 3 or more EarthCaches.
Permission: 
References:
Wikipedia.org
virginiaplaces.org
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