Lake Drummond and Great Dismal Swamp
Orthophoto and topographic map of Dismal Swamp and Lake Drummond
Lake Drummond is named for a former North Carolina governor who had been an ally of Governor Berkeley of Virginia, but then chose the wrong side in Bacon's Rebellion in 1676. After the rebellion collapsed, the last words of Governor Berkeley to William Drummond were "Mr. Drummond, you are very welcome. I am more glad to see you than any man in Virginia. Mr. Drummond, you shall be hanged in half an hour."1
The lake is one of just two natural lakes in Virginia. Mountain Lake (in Giles County) may have formed on Salt Pond Mountain by eroding a basin into an unusual structure in the Clinch Sandstone formation. There, cracks in the sandstone have formed a depression allowing water to seep underground, etching a lake basin in the bedrock. Intermittently, the cracks are opened (allowing Mountain Lake to drain and be replaced by a meadow) or blocked (causing the lake to reform).
southeast Virginia, showing Lake Drummond and Union Camp holding ponds to west (at City of Franklin, near Blackwater River)
Source: NASA -
Stennis Space Center
The creation of Lake Drummond is even more mysterious. Geologically, Lake Drummond is an unusually large (3,108 acre) open body of water on the Coastal Plain, east of the Suffolk Scarp. At normal water levels, the lake is 6-7 feet deep and the surface is 18 feet above sea level. There is little topographic relief in the area; elevation drops at one foot per mile near the lake.2
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There's no obvious reason for one big lake to exist in the middle of the Great Dismal Swamp, which extended all the way to Back Bay/Albemarle Sound in the colonial era. There is no network of streams draining a watershed upstream and emptying into the lake. Lake Drummond is a high point in the middle of the remnants of the swamp.
In fact, ditches - including some dug during the time when Virginia was a colony, such as "Washington Ditch" initiated by George Washington - are supplied naturally with water that drains by gravity out of the lake. When lake level drops to 15.75 feet, the U.S. Army Corps of Engineers stops releasing water from Lake Drummond to supply the Dismal Swamp Canal. As described by the US Fish and Wildlife Service:3
- The Great Dismal Swamp is less than 9,000 years old; it was formed on a hillside instead of a basin and without the benefit of rivers flowing
into or beside it.
The origin of the swamp dates back to the end of the last ice Age:4
- Evidence indicates that the Dismal Swamp first began to develop along streams 11,000 to 12,000 years ago. A previous ice advance had left the area with characteristic boreal vegetation of jack pines and spruces. Over a period of 3,000 to 4,000 years the boreal vegetation was replaced by northern hardwood species that, in turn, was replaced by oaks, hickories, and other endemic southeastern species.
- The swamp gradually expanded westward along watercourses and peat began to accumulate. By 3,500 years ago, peat had blanketed the present-day Dismal Swamp, the water regime was saturated, and the oak-hickory forest was replaced by a cypress-gum swamp.
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Geologically, the swamp and lake formed on top of coarse sand that is very permeable, but with layers of clay and silt that block water flow. An organic layer of peat has accumulated at the surface, and is up to five feet thick. Underneath the peat is the Sandbridge Formation, with upper layer of silty clay and a lower layer of sand. the next layer down is the London Bridge Formation, mostly clay silt, and then layers of sand and silt called the Norfolk Formation. The Norfolk Formation is exposed to the west of the swamp at the Suffolk Scarp:5
- This is the groundwater recharge area for the aquifer... Groundwater input from the Norfolk Formation accounts for the majority of water that upwells in the swamp.
One possibility: Lake Drummond was formed when a natural fire burned a "hole" in the peat of the Great Dismal Swamp. In 2011, during a severe drought, one of the largest wildfires in the modern history of Virginia burned 6,500 acres of the swamp. The "Great Conflagration" of 1923-26 was probably even more significant.6
Perhaps 9,000 years ago, a lightning strike triggered an extraordinary fire that burned hot enough to destroy the peat layer, down to the clay confining layer that keeps the water in the swamp from draining into the sand underneath. Such a fire could have carved out a bowl within the deep peat, creating a hole that developed into Lake Drummond.
ditches drain Lake Drummond, especially Feeder Ditch connecting the lake to the Dismal Swamp Canal at Arbuckle Landing
Source: US Geological Survey,
Lake Drummond 7.5x7.x topographic map (2011)
Lake Drummond resembles may other elliptical "bays" or small lakes on the Coastal Plain of the Eastern United States, from Florida to New Jersey, with a southeast-northwest orientation. They might have formed naturally in the Pleistocene as the climate changed, perhaps comparable to the formation of modern lakes on the Arctic Coastal Plain. The elliptical pattern could have been caused by winds blowing from the southwest and forming sand ridges, which have since been vegetated - and in some cases flooded to form lakes - as rainfall increased in the last 20,000 years.7
Another possible cause is that Lake Drummond was formed by an icy comet/meteor that broke up in the atmosphere and peppered the Coastal Plain. Meteorite fragments are rare in the area, so there is insufficient evidence to claim the lake is a meteor crater. However, shock waves from a comet exploding above the surface of the earth could have carved out the initial depressions, which then filled with water and have been covered with vegetation.
Fragmentation of an extra-terrestrial comet in the atmosphere might explain the regular pattern of the ellipses, their large number (roughly 500,000), and the absence of meteorite fragments. The Younger Dryas period of global cooling, 12,800 years ago, could have been triggered by such an event. Lake Drummond could be a larger-than-usual Carolina Bay, formed recently as earth's surface was disturbed by a dying comet.8
Today, Lake Drummond is in the middle of the Dismal Swamp National Wildlife Refuge. The Union Camp Corporation, a lumber company, donated 49,000 acres of the logged-over swampland to The Nature Conservancy in 1973, and then the non-government organization transferred the property to the Federal government. Further land acquisition has expanded the refuge to over 110,000 acres.9
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One goal of the US Fish and Wildlife Service is to restore the natural flow of water in the swamp, undoing the effects of ditches and logging roads that have created drier-than-natural and wetter-than-natural areas. The organic soils in the swamp are normally 85-95% water. When they dry out, the soil particles alter into a granular form that will not absorb water even after water levels rise again, and oxidize away. Keeping the soils saturated is essential for minimizing the intensity and size of wildfires in the Great Dismal Swamp.10
Hurricanes and major forest fires, influenced by the altered drainage, alter the ecosystem even more rapidly. in 2003, Hurricane Isabel flattened 80% of the purest cedar stands in the refuge. Fires - and prevention of fires - threaten the continued existence of the Atlantic white cedar plant community:11
- Many communities within the GDS [Great Dismal Swamp] are pioneer or early successional species, which will be replaced by longer-lived climax species if not disturbed. These communities include the Atlantic white cedar, shrub pocosin, marsh and sphagnum bog. Each of these vegetative communities was historically a result of wildfire and/or maintained by fire. Wildfires have been aggressively suppressed since the 1940’s resulting in reduced size and vitality of dominant species. With the changes in water regime throughout the swamp and the surrounding urbanization, permitting drought-driven wildfires to
burn today is not an option.
- Management of these communities must create the disturbance required for regeneration or maintenance. Strategies include the use of herbicides, and/or timber sales to reduce competition, surface preparation completed by scarifying with heavy equipment, and/or carefully conducted site preparation prescribed burns...
- The refuge cannot manage the adjacent cropland to slow incoming surface water, nor can it abandon or remove the roads within the swamp because compaction has already altered the substrate and road access must be maintained to fight wildfires. The refuge cannot abandon the ditches because the clay-confi ning layer cannot be replaced over the aquifer.
- The refuge can operate and maintain a number of water control structures that slow discharge of both surface and ground water from the swamp and serve to mitigate many of the impacts of these developments.
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Jerico Ditch, Great Dismal Swamp National Wildlife Refuge
Source: US Fish and Wildlife Service, National Digital Library
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- Why are there only two natural lakes in Virginia?
- Over 200 million years of steady erosion in Virginia has allowed streams to etch their way into every Virginia valley. The stream channels have drained whatever lakes may have formed long ago in the last major orogeny, when the Appalachian Mountains were lifted up and topography transformed. In the most recent Ice Ages, no new lakes in Virginia were scoured out by the ice sheets - in contrast to places such as Minnesota, where melting glaciers transformed the landscape and created lakes (including the Great Lakes) in the last 100,000 years.
- The millenia of erosion destroyed all lakes created since the Appalachian Orogeny, and the two natural lakes present today appear to have been created by recent events. All other "lakes" in Virginia, including small ones such as Burke Lake in Fairfax County and large ones such as Smith Moutain Lake near Roanoke, are human-made reservoirs created by building dams and flooding valleys.
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Lateral West Forest Fire burns towards Corapeake Ditch at Great Dismal Swamp National Wildlife Refuge, 2011
Source: US Fish and Wildlife Service,
National Digital Library
Links
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References
1. Dictionary of Virginia Biography. (2010, June 9). William Drummond (d. 1677). Retrieved September 12, 2010, from Encyclopedia Virginia: http://www.EncyclopediaVirginia.org/Drummond_William_d_1677 (last checked September 12, 2010)
2. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," US Fish and Wildlife Service, July 2006, p.36, p.44, http://library.fws.gov/CCPs/GDS/greatdismalswamp06.pdf (last checked September 9, 2012)
3. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," p.41, p.44
4. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," p.60
5. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," pp.37-38
6. "The Great Dismal Swamp a year after the fire," Chicago Tribune, August 4, 2012,
http://www.chicagotribune.com/news/dp-nws-great-dismal-swamp-20120804,0,6818233,full.story; "Great Dismal Swamp wildfire still burning after more than 2 months," The Washington Post, October 6, 2011, http://www.washingtonpost.com/national/health-science/2011/10/05/gIQALlJYRL_story.html (last checked September 9, 2012)
7. Robert E. Carvera, George A. Brook, "Late pleistocene paleowind directions, Atlantic Coastal Plain, U.S.A," Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 74, Issues 3–4 (30 November 1989), http://dx.doi.org/10.1016/0031-0182(89)90061-8 (last checked September 9, 2012)
8. James H. Wittke, James C. Weaver, Ted E. Bunch, James P. Kennett, Douglas J. Kennett, Andrew M. T. Moore, Gordon C. Hillman, Kenneth B. Tankersley, Albert C. Goodyear, Christopher R. Moore, I. Randolph Daniel, Jr., Jack H. Ray, Neal H. Lopinot, David Ferraro, Isabel Israde-Alcántara, James L. Bischoff, Paul S. DeCarli, Robert E. Hermes, Johan B. Kloosterman, Zsolt Revay, George A. Howard, David R. Kimbel, Gunther Kletetschka, Ladislav Nabelek, Carl P. Lipo, Sachiko Sakai, Allen West, and Richard B. Firestone, "Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago," Proceedings of the National Academy of Sciences (PNAS), published ahead of print May 20, 2013, http://dx.doi.org/10.1073/pnas.1301760110; J. Ronald Eyton, Judith I. Parkhurst, "A Re-Evaluation Of The Extraterrestrial Origin Of The Carolina Bays," April 1975, http://abob.libs.uga.edu/bobk/cbayint.html; Michael Davias, "Correlating the Orientation of Carolina bays to a Cosmic Impact," http://cintos.org/SaginawManifold/introduction/index.html (last checked May 26, 2013)
9. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," p.4
10. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," pp.38-39
11. "Great Dismal Swamp National Wildlife Refuge and Nansemond National Wildlife Refuge Final Comprehensive Conservation Plan," pp.21-22, p.59
Lakes, Dams, and Reservoirs
Draining the Swamps of Virginia
Rivers and Watersheds
Virginia Places
