The Wisconsin Glacier Leaves Us Reminders

 

On the road… again!

Afghanistan to Zambia

Chronicles of a Footloose Forester

By Dick Pellek

 

 Living on the Terminal Moraine

 

After a short one-page article about terminal moraine boulders in Netcong, New Jersey was published in the geology section of About.com in April 2011, it now becomes apparent that a short “talk story” should be written. A few ideas are matter-of-fact statements that might not garner much attention because not many people know where Netcong is, and even fewer people care.  Family and friends who are Facebook subscribers, and people who live in Netcong, New Jersey can at least recognize the Main Street entrance to St. Michael’s Church parking lot in the photo that accompanied the article.  So, this Chronicle entry is intended to awaken their interest to a past that is part speculation and part reverie of a child growing up in Netcong.

In earlier versions of the Netcong Chronicle about Living on the Terminal Moraine, the Footloose Forester described some aspects of geological history, as provided by a geologist from the US Geological Survey, as follows: … the site of the excavated hillside behind St. Michael’s Roman Catholic Church exposes mixed, unsorted stones, boulders and other glacial till material carried down by the Wisconsin Glacier more than 25,000 years ago. After 700-1000 years, the glacier started to retreat out of New Jersey and was gone about 21,000 years ago….

 

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Fox Glacier, an example of terminal moraine topography

Today, parishioners who use the parking lot off Main Street, or enter the lot from the Church Street entrance, will notice a dozen or more boulders that weigh several tons. A few are 5-6 feet high.  What is different about these boulders is that most of them were excavated from below ground, thus are fresh in the sense that they lack signs of weathering and exposure such as the presence of moss.  A few of them were partly buried, so will show both the weathered faces and the unweathered portions that were buried.  That is certainly the case with a large pointed boulder that we used to refer to as the Castle.  We children growing up on Church Street had to take two or three steps to mount the Castle to then sit in a rough seat-like cradle that we called the throne.  The Castle was perhaps the largest of the boulders because when you walked around it, you could see that its base was deep into the ground.  On the other hand, the Loaf of Bread was also a monster but it was almost entirely on the surface.  It still required mounting from the front or the back because the sides were too tall and too smooth to get a grip.  The Loaf of Bread was shaped almost exactly like a loaf of bread and it was everybody’s favorite.

Another remarkable fact about those dozens of huge boulders, and more than a hundred smaller ones, is the disparity of their appearance when you now see them standing side by side. A pink granite is standing next to a specimen of gneiss, next to another boulder of reddish sandstone. There are also other species that are easy to tell apart: conglomerate, shale and limestone. They were all excavated from the same trove of moraine materials that were transported on glacial ice and finally dumped there about 25,000 years ago. 

To tell that story convincingly, however, requires a good deal of speculation.  To date there is no detailed description of the process by which a veritable treasure trove of glacial materials was deposited in Netcong, so there is little likelihood that the Footloose Forester will be challenged regarding his views.  And his speculative view is this:  Some estimates put the thickness of the ice sheet of the Wisconsin Glacier at over 1000 feet; and as it moved slowly southward out of Canada it sheared off rock material from some ridges and even the tops of some hills.  Pebbles, stones and even some boulders plucked from rock outcrops were incorporated into the stream of migrating ice. Most transported material was located in parallel bands at the edges of the ice sheet where it came in contact with vulnerable land features. Those parallel bands are known as lateral moraines and examples can be seen in photographs of alpine glaciers.

The Footloose Forester speculates that, as the Wisconsin Glacier neared its terminal point in the vicinity of Netcong, the ice was by then so weakly crusted and so thin that it dropped a large portion of its transported sediments in a few places when topographic irregularities acted as catch basins. If the trove of boulders found between Church Street and Main Street was along and above a lateral moraine, the deposition could include many species of rocks acquired along its path. One final speculation: as the microclimate warmed to the point of melting the glacier as it slowed to a halt, the force of gravity caused an overall settling of the heavier materials into a pocket at the site of the parking lot, while lighter materials were washed out into outwash plains lower in the terrain. The existence of kames in the outwash plains of the region is well established.

Storytelling and speculation aside, any layman can see that the dissimilar rocks ringing the parking lot at St. Michael’s are uncommon in their collective appearance.  Most show rounded surfaces on more than one side, suggesting polishing in transit rather than being part of the basement complex. Now that they have been excavated and inadvertently used as lane barriers; or pushed aside because of their unmanageable size; or marshaled into decorative mounds of shards, the visitor can experience an outdoor geology lesson with many of the specimens directly underfoot.

Before-after satellite photos in both Google Earth and in Bing Maps will allow computer users to see the site before the excavation began in 2006; during an intermediate stage of landscaping for the parking lot; and a post-construction phase. The enduring lesson in glacial geology, however, comes when you sit on one of those boulders and inspect a shard of green granite in one hand and a limestone in the other.

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Comments 1

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Tom Cormier (website) on Wednesday, 04 January 2012 21:50

You need to find something to keep you busy. This is incredible history and I can only hope the congregation appreciates it or have been told this amazing story.

You need to find something to keep you busy. This is incredible history and I can only hope the congregation appreciates it or have been told this amazing story.