“Manhattan prong,” this series of metamorphic rocks extends from southwestern PAGE 15 Village of Croton-On-Hudson, NY Figure 3.1. Local Context Village Boundary 0 12500 25000 ft Source: New York State Atlas and Gazetteer, DeLorme Mapping Company BFJ Buckhurst Fish & Jacquemart, Inc. 16 CROTON COMPREHENSIVE PLAN Connecticut, northern Westchester County, south to the southern tip of Manhattan Island. The valleys are principally marble and more easily eroded than the schists and gneisses of this unit's higher elevations. The hills are primarily erosion-resistant and tightly folded metamorphic rocks, mostly gneisses and schists with some local deposits of quartzite, overlain with till and coastal plain deposits; they represent the vestiges of ancient, worn-down mountain ranges. Croton-on-Hudson’s high points, and most of the exposed rock, are made of Manhattan Schist, a rock type that is the product of dynamic metamporphism dating back over 360 million years ago. Other outcrops in the Village include Fordham Gneiss, with Inwood Marble in the lower, flatter areas. In addition to these features, glacial erratics, or boulders left in place after the glacier melted, can be found all over the Village. Remains of glacial kettles, or kettle ponds, are present in the Croton-on-Hudson area as well. The present configuration of Croton-on-Hudson’s land and the present course of the Hudson River were formed over the last 1.5 million years. There were four periods of glaciation in the Hudson River Valley during this era, with each period involving numerous advances and retreats of the continental ice sheets. These glaciers were the source of many streams in the area, and also deposited glacial sediments (moraines) as they retreated. Croton Point was formed during the Pleistocene era as a glacial-alluvial delta, created by the runoff from the glacial streams following the glacial retreat, at a time when the water level of the Hudson River (then a swollen “Lake Hudson”) was approximately 100 feet higher than the current water level. In general, depth to bedrock tends to increase as one goes downslope, leading to alluvial deposits that form the banks of the Croton and Hudson Rivers. In addition, due to the collapse of the th original Croton dam during construction during the mid-19 century, damned water broke free, rushing massive quantities of soil, sediment, trees, and even houses, downstream. During this mini-flood many thousand tons of sediment were moved from the Croton River channel to the mouth of the Croton River. b. Topography and Drainage Areas Croton-on-Hudson’s topography includes low lying areas along the Hudson River, Route 9, and the railroad tracks, a fairly deep ravine along the Croton River, and a plateau along its northern boundary that in some areas reaches elevations up to 500 to 600 feet within a mile of the Hudson River. This steep terrain has formed a series of ravines and the following watershed drainage areas within the Village: PAGE 17 CROTON COMPREHENSIVE PLAN • • • Hudson River Basin: draining to the Hudson River to the west Croton Gorge Basin: draining to the Croton River and Bay to the south and east. Furnace Brook Basin: draining to the north where the drainage terrain is less steep and flows to lakes and streams, including the Furnace Brook and Lake in Cortlandt. Croton-on-Hudson’s topographical features also create dramatic views that orient most of the Village toward its two riverfronts: the steeper elevations in the northern section of the Village slope down to more level ground to the west along the Hudson and to the southern portion along the Croton River. c. Soils Soils within the Village of Croton-on-Hudson are typical of those in Northern Westchester, due to similar bedrock structure and glacial activity. In general, the Village is composed of upland soils associations, with glacial outwash, and organic materials along the Hudson River shoreline. Most of Croton-on-Hudson’s soils are glacial in nature, consisting primarily of till (soils containing rocks and pebbles of irregular size), finely sorted soils (pebbles and stones of regular size), and fine outwash sands. The shoreline of the Hudson River is a mixture of glacial soils, alluvial deposits, and organic materials. As noted above, Croton Point was formed as a remnant of a glacial delta. Given the irregular bedrock in the Village, trees and ground covering plants are crucial for slope stabilization. The unstable slopes in the Village can result in “slumping,” which produces cracks and gaps in sidewalks, retaining walls, and railroad ties; many Village roads show the results of frost heaving in the late winter and early spring. d. Water Resources The water resources of the Village define much of its natural character: Hudson River and Croton Rivers and associated freshwater wetlands, the ponds at the north end of the Village, and several smaller streams that run from the higher elevations to the lower rivers, and their wetlands. The Croton Water Control Commission reviews