Dismal Swamp Markers - Investigative Geology
Introduction
Before you stands the murky coffee colored waters of the Dismal Swamp Canal. The first written record of the Canal exists in a journal from 1728 in which Mr. William Byrd II wrote in part:
"It wou'd require a great Sum of Money to drain it, but the Publik Treasure cou'd not be better bestow'd than to preserve the Lives of His majesty's Liege People, and at the same time render so great a tract of Swamp very Profitable, besides the advantage of making a Channel to Transport by water-carriage goods from Albemarle Sound into Nansimond and Elizabeth Rivers in Virginia."
Over the next 76 years the idea took hold in the region and in 1784 the Dismal Swamp Canal Company was incorporated. Construction on the canal began in 1793 and was completed in 1805. The canal was dredged and deepened in the early 1810s in order to accommodate more traffic and in 1819/1820 granite locks were added to further increase the size of vessels that could fit through the canal.
Before you stands a granite mile marker. At one point in time these mile markers served to help guide ships from one end of the canal to the other, helping them gauge distance traveled and distance remaining in their journey. Despite all the literature on the canal, surprisingly little is known about these markers. The pamphlet "Stone Mileposts along the Dismal Swamp Canal" explores the mystery of these markers, however a definitive answer on where these granite pillars originated from! As you explore this Earthcache you will be exposed to the predominant theory on their arrival to the area and assist in classifying these markers. Let's jump into the geology!
Local Geology
In order to understand why there is a shroud of mystery around these stones, we need to examine the local geology. The Southeastern portion of Virginia is predominantly made of sand, mud, silt, swamp and gravel.
As you can see from the above image the nearest place to obtain granite is out past the Richmond area. Wherever this granite originated from, it wasn't sourced locally. According to Virginia Canals and Navigation Society the leading theory for where these stones originated concerns the construction of the locks in 1819-1820. There are no mentions of the canal markers in local historic records predating the installation of the locks, the assumption can therefore be made that the markers were installed with the remnants of the granite used to install the locks. These locks were built of "stone material brought from Newark, New Jersey and cut on the spot; the backing or outside stone, from the head of the tidewater on Susquehanna, Patowmac, and James River."
While this theory aligns chronologically with the construction of the canal, let's take a closer look and see if this theory is supported by the geology as well.
New Jersey Granite
While our first person source clearly tells us where the granite originates from (Newark, NJ), there are four distinctive types of Granite that are naturally occurring in the New Jersey Highlands: Byram Granite, Lake
Hopatcong Granite, Mount Eve Granite and Pompton Pink Granite.
- Byram Granite (or Byram Suite Granite) is the most abundant type of granite in the New Jersey Highlands. It is characteristically gray in color and medium to coarse grained with a composition of quartz, feldspar and hornblende. It can be found in tens of miles long stretches throughout the Highlands of New Jersey.
- The Lake Hopatcong Granite is also medium to coarse grained with similar composition of quartz and feldspar, however it lacks hornblende and substitutes it with pyroxene which gives it more of a greenish coloration. Much like Byram, it can be found in tens of miles long stretches throughout the New Jersey Highlands.
- Mount Eve Granite is confined to the Northwestern region of the Highlands where it forms a series of bodies that continue north into New York. It is pinkish-white in coloration and medium to coarse grained. It is composed of quartz feldspar and hornblende.
- Pompton Pink Granite is the rarest of all as it is located only at Pompton Junction in Passaic County and Riverdale in Morris County. Pompton Pink Granite is pink to pinkish-white with light green mottling. It is coarse grained and composed of quartz and feldspar.
Logging Requirements
In order to log this cache as a find and earn your smiley you must answer the below questions. Please send your answers in a timely manner to the Cache Owner who can be contacted via the message center (link to profile at the top of this cache page). You may log your find immediately, no need to wait for your answers to be validated - I will contact you if there are any issues. If you fail to submit your answers in a timely manner your log may be deleted.
- Is the granite mile marker course, or fine grained. Estimate the size of the average grain.
- What is the predominant color of the granite marker. Are there any other shades of coloration in the granite?
- Based on the reading material above and your answers to questions 1 and 2 determine what type of granite was purchased and installed along the canal in the 1820s.
- Take a photo of yourself, a personal object or your GPSr with the canal in the background. Do NOT include any part of the granite maker in your photo!
References
- "Stone Mileposts along the Dismal Swamp Canal" Prepared for the Virginia Canals and Navigation Society by George V. Ramsey.
- https://www.state.nj.us/dep/njgs/enviroed/newsletter/v7n1.pdf
- https://www.nj.gov/dep/njgs/enviroed/infocirc/pompton.pdf
Permissions: Chesapeake City has granted blanket permission to place caches in all city owned parks with only two notable exceptions (Additional requirements exist for Northwest River Park and Centerville Park). Always seek permission prior to placing an Earthcache! For more questions on permission, please see the regional wiki or the Geocaching Guidelines!