Published in Trumansburg Free Press April 13, 2005
|Land & People
Disrupting the Grid
by Bill Chaisson
Last week I drove south down Halseyville Road from Rt. 96 and got out of the car at Perry City Road. I held my compass parallel with the shoulder of Halseyville Road; it pointed almost directly north-south. It is actually oriented a couple degrees west of due north, which may be caused by changes in the relative position of the geographic and magnetic poles in the two centuries since the Military Tracts were surveyed.
The late 18th century was the height of the Enlightenment and the governments of the United States and New York were determined to impose order on the ostensible chaos of the natural landscape of the Finger Lakes. A look at a map will show you that they, in part, succeeded. The rural roads are laid out on a rather strict grid over much of the territory between Cayuga and Seneca Lakes.
Halseyville Road flies like an arrow almost due south across the town of Ulysses, crosses Rt. 79, turns into Rt. 327 and just before it reaches the village of Enfield it begins to veer to the west. From there to its end at Rt. 13 the road follows the landscape, not the Enlightenment.
Immediately after passing the Enfield School you cross over Five Mile Creek. The stream under the road and adds to the flow of Enfield Creek. Between the village of Enfield and the turn-off to Trumbull Hill Road, the drainage of Enfield Creek becomes ‘deranged’. The creek just can not seem to get where it is going and it sprawls across the land as a wetland that is a mixture of swamp (wooded) and marsh (herbaceous vegetation).
So, why does the military tract grid fall apart below Rt. 79 and why does the Enfield Creek drainage become deranged? Because of the Valley Heads Moraine. Approximately 14,000 years ago, four thousand years after it began its retreat from its ‘terminal’ position in Pennsylvania, the latest continental icesheet (the Wisconsinan) stalled,
|neither advancing nor retreating. It was melting at exactly the same rate as it was
being pushed forward from its origin in northern Canada, so it just sat
there and extruded a disorderly combination of boulders, sand, silt and
mud for several hundred years. When it resumed its northward retreat, it
left behind a linear pile of unsorted sediment that winds for hundreds
of miles across New York, blocking the south ends of all the valleys of
the Finger Lakes and deranging drainages all along the way.
The Valley Heads Moraine does not make up all of the hills. It is, rather, a very thick icing over a cake of Portage and Chemung Group sandstones and siltstones. The glacial sediment is deployed like a desperate baker using frosting to conceal the imperfections of cake that has been dropped more than once. There is evidence that during the withdrawal from the Valley Heads Moraine, a melting lobe of glacial ice sat in the valley crossed by Enfield Center and Bostwick Roads. The retreating ice, confined between the high ridges on either side, shed meltwater into streams that ran between its flanks and the valley walls. The mud and silt were carried away by the currents and only sand, pebbles and cobbles are deposited in rough layers. When the last of the ice melted away, these deposits, called ‘kame terrraces’ were left pasted to the valley walls.
South of the village of Enfield several gravel pits have operated and are operating to take advantage of the presence of this relatively well sorted sediments. The most easily seen is on Hubbell Road. A number of conical hills also dot the area. These are likely ‘kames’ proper. These are sediments that collected in depressions within the melting ice and were then left on the landscape when it retreated.
This pattern can be repeated all across the state. Drive south on a dead straight road through the surveyed military tract. When you reach the moraine and the road starts to wind around obstacles. The obstacles are valleys carved by the glacial ice and clogged by the sediment it left behind. Sediment extruded directly from the ice (moraine), unsorted and unlayered, and sediment deposited by the glacial meltwater, sorted, layered, and, in its own way, orderly.
Hibernian Weather Channel Productions
Last revised: May 11, 2005