Quansoo Beach: Recent Geological History

A Brief Analysis by Tim and Alex Cohn
25 August 2000



Cautions:



The Issue:

Over a hundred years ago, Henry Whiting reported that the South Beach of Martha's Vineyard was rolling northward at a rate of approximately 5 feet per year (Whiting 1888).  Although the geology of beach recedence is relatively well understood, this situation is somewhat unusual and of sufficient practical interest -- particularly to  owners of property in Quansoo -- to justify some investigation.  In any case, land that evolves from backwoods through beachfront to submarine property clearly deserves special treatment -- not even considering the legal issues that it raises.  The purpose of this page is to document, in a crude way, what has occurred during the hundred years since Henry Whiting first called attention to this phenomenon.

The Geologic History of Cape Cod and Martha's Vineyard:  Some References

Fortunately, a lot of good material has already been written about the geologic history of the Cape Cod region, of which  Martha's Vineyard and Nantucket are a part.  For starters: Geologic History of Cape Cod, Massachusetts, by Robert N. Oldale of the U.S. Geological Survey, provides an excellent introduction.

After reading about the regional geological history, you should take a few minutes to read the fascinating early account of Martha's Vineyard's beaches contained in Whiting (1888); it explains almost everything!

Finally, an excellent review of  coastal issues affecting the Nation can be found in Coasts in Crisis, by S. Jeffress Williams, Kurt Dodd, and Kathleen Krafft Gohn.

The Cartographic Record of South Beach

The Island of Martha's Vineyard appears, at least in concept, on many early maps of New England.  Some of these are available on the web at http://www.vineyard.net/vineyard/history/maps.htm.  Of particular interest is the J. Reid map of 1796, which shows that at one time all of the ponds on the South shore of Martha's Vineyard were connected.  This is consistent with reports of ice skating along the sound  from Chilmark to Edgartown.  It also explains the origins of the names for some isolated ponds such as Long Cove and Quename Cove.

High-accuracy mapping of Martha's Vineyard began in the 19th century.  The Island has been surveyed and mapped at least three times by the U.S. Geological Survey:

These maps have been periodically "photoinspected" and revised, most recently in 1977.  All of the maps are available from the USGS.

Aerial Photographs of Martha's Vineyard

The National Aerial Photography Program has been operating since the 1940's, and the Island has been photographed periodically ever since.   A set of these photographs have been ordered and will be available on this web page in the near future.  For now, the best available recent aerial photograph is from 1994 (see below).
 

The Rate of Beach Recedence

A quick analysis was conducted comparing the 1887 map (right) with the 1994 aerial photograph.  This reveals that the Quansoo Beach migrated to the north by approximately 500 feet during 107 years, for an average rate of slightly less than 5 feet per year.  This is consistent with Whiting's findings: Whiting (1888) estimated that in the 40 years between 1846 and 1886 the beach had "rolled" between 175 and 200 feet, an annual average of slightly less than 5 feet.

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1994 Aerial Photograph                                                               1887 Map

It is also interesting to note some of the consequences:  In 1887, Chilmark Pond, Quename Cove, Blackpoint Pond, Tisbury Great Pond, and Long Cove were connected by natural channels.

1942 Map

By 1942 (above), the beach had moved northward by about 250 feet and apparently had cut off essentially all of the links.  The two that remained, connecting Black Point Pond to Tisbury Great Pond to Long Cove, appear to have been constructed.
 

Conclusions

Various records indicate that South Beach at Quansoo has been "rolling" northward at a fairly steady rate of approximately 5 feet per year for the past several hundred years.



 

Web Resources



Page created 25 August 2000;  Page last modified  13 September 2000

Please email comments or suggestions to Tim Cohn at: tim@timcohn.com