“Glacial Erratics and Fieldstones” Boulders and other rocks broken off and carried by ice sheets covering this region were left in place when the glaciers melted. Geologists call these “erratics.”. Early settlers called them “fieldstones” and used them to build their house walls.
During the last Ice Age as ice sheets moved southward over our region, glaciers broke off and carried pieces of the underlying bedrocks. When the ice melted, the fragments were left scattered over the surface. Geologists call such transported rocks “glacial erratics,” because they are different from the native bedrock. Most of these were pebble- and boulder-sized, mixed into sands and clay. A few are more than 10 feet high, such as Haring Rock in the Tenafly Nature Center (Fig 1A) and Tripod Rock in Sussex County (Fig. 1b). Fig. 2 shows images of erratics of various sized in a state park.
As the ice sheets moved, rocks underneath often scratched parallel grooves in the bedrocks. These are called “glacial striations” (Fig. 3).
Until Englewood Township was formally organized in 1859, most of what is now our City consisted of small farms which stretched from Overpeck Creek uphill to the Hudson River. Like other early European settlers, the farmers needed to move the boulders and other glacial erratics to create plowable fields. Rocks were gathered to build stone walls typical of New England and other glaciated parts of the Northeast. (Fig. 4).
Many of the stones collected from the fields (“fieldstones”) were trimmed to make the walls of homes and other buildings. Many of the remaining buildings from the Dutch/English colonial period and the early 19th Century here in Englewood and vicinity incorporated “fieldstones” in their walls. Two examples include the Lydecker House (Fig. 5) and the English Neighborhood Union School (Fig. 6). The original section of the Lydecker House was built in 1803. Until late in the 20th Century, it was occupied by the same family. Now it houses the Southeast Senior Center for Independent Living. The school building was originally constructed about 1808 near the Liberty Pole (Monument Circle). Later in that century, it was dismantled stone by stone and rebuilt on Tenafly Road near Ivy Lane as a private residence.
Fieldstones were also used to construct many of the impressive mansions built in the 19th and 20th Centuries. Before construction of the Palisades Interstate Park and Parkway, there were huge edifices built along the top of the cliffs using the locally available rocks, along with quarried stones. Most of these were demolished when the park and roadway were built. But within Englewood, many of the stately homes from that period still exist, examples of the glory when Englewood was known as “The Bedroom of Wall Street.”
Fig. 1. Haring Rock in Tenafly Nature Center
Fig. 1B. Tripod Rocks on Pyramid Mountain, Sussex Co. http://www.njskylands.com/odhiketripod
Figs. 2A and 2B. Glacial erratics near Monksville Reservoir
Fig. 3. Glacial striations (faint parallel scratches cutting across cracks, with pen for scale and orientation) on the diabase bedrock near the Flat Rock Book Nature Center Interpretive Building. The striations show the glaciers moved toward the southeast in this region.
Fig. 4. Typical stone walls
https://newengland.com/today/living/new-england-stone-walls/
Stone walls next to the original 1st Presbyterian Church on Palisade Ave. The walls are still in place.
http://www.cityofenglewood.org/content/9262/11544/default.aspx
Fig. 5. Lydecker House images
Fig. 6. English Neighborhood Union School Originally constructed in 1808 near Liberty Pole Tavern (Monument area) and moved to its present location on Tenafly Rd. near Ivy Lane in 1850. Used as a school until 1897; now a private residence.
More information
Wikipedia “Glacial Erratic”
NJ Geological Survey “Glacial Sediments and the Ice Age in NJ”
NJ Meadowlands Commission “History of the District”
Palisades Interstate Park Commission NJ “Ice, on the Rocks”