New York state glacier history and evidence

¶ … glaciers in the development in New York's present geology. Take a drive around just about any part of New York State and you can find evidence of glacial activity in the past. There is evidence even in New York City's Central Park of this glacial activity that molded and shaped the Empire State into its present geological format.

One way to spot hints of glacial activity is to look at the faces of the rocks and the surrounding landscape. The surface of the rocks will be smooth, almost as if they were sanded with a giant piece of sandpaper (which, in effect, they were). There are often scratches or grooves in the surface of the rocks, as well. The landscape surrounding these features will often be marked by rolling hills, valleys, and even elongated and oddly shaped hills. This occurs because the glaciers, as they moved into and then receded from an area, they acted as giant files against the soil and rock. They push rocks along, acting like sandpaper and smoothing the surface of the surrounding area, and they retreat and return gradually, so the changes are far less pronounced than other types of geologic activity.

There is another way to tell an area has been formed or molded by glaciers, and that is to look at the layers of soil in an area. Several geologic experts write to remove the soil, and "[O]bserve a sharp boundary between the soil and the rock, and not a gradational change. This indicates that the soil has not developed from the weathering in situ of the rock, but rather that the soil has been transported to its present location by some transporting agency" (Amos et. al, 1968). The transporting agency in this case is a slow-moving glacier, gradually moving across the landscape and shaping the face of the area for eons to come.

The evidence around the state suggests that glaciers covered the entire area several thousand years ago. Another writer notes, "During the last ice age, which peaked approximately 18,000 years ago, ice in what is now New York City lay as much as a mile thick" ("Explaining Variations in Ice," 9). These glaciers were formed by falling ice and snow. As these waters froze, they trapped soil, rocks, and debris within them, and it is this trapped debris that scours the landscape and creates the very recognizable signs of glacial activity on the geology. Eventually, as the glaciers melted, they deposited this debris throughout the state in areas called "terminal moraines." The authors continue, "Large morainal deposits are found south of the Finger Lakes area, and extend in places to the Pennsylvania line" (Amos et. al, 1968). This indicates the activity and influence of glaciers throughout the area, as morainal deposits can be found throughout the state if you know where to look. Another sign of this glacial activity is deep depressions in the landscape. Today, many of these deep depressions are lakes and streambeds that were formed as the glaciers carved their way throughout the state.