The Sourland Mountain has a long and varied history in the west-central region of New Jersey. The area is bordered by multiple homes and is a recreation playground for many local residents. Hikers, bikers, naturalists and many more outdoor enthusiasts come to the Sourland Mountain Preserve to enjoy the many trails, wildlife, and natural wonders this preserve has to offer. The individual or group looking to get a worthwhile view of the preserve only needs to stay on the infamous five mile loop known as the Ridge Trail. The Ridge Trail offers the sightseer all the preserve’s wonders which include Devil’s Half Acre Boulders, the Texas Eastern Pipeline (offers views on NYC on a clear day), many brooks and small waterfalls. Lastly but not the least significant is the geological occurrence of Roaring Rocks.
Roaring Rocks is a spectacular phenomenon that has amazed many travelers who have made the trek to this area. Famous individuals such as President Grover Cleveland and Albert Einstein along with numerous actors and artists have made their way to see the Sourland Mountain and Roaring Rocks. This field of enormous boulders perplexes many and the same question always looms, “How did these massive rocks get here?”
Many have asked the question of how these massive boulders get here. A simple geological answer would be to point to glacial movement. However, this is not the case due to the fact the glaciers of a million and a half years ago did not reach down this far to the mountain. Even though glacial ice was not the culprit, other forms of ice had something to do with the formation of these rocks. Our answer perhaps is found in an investigation conducted by George M. Banino in 1969 for the New Jersey Geological Survey.
Banino did not start his research with the rocks themselves but looked to the water beneath the rocks, Roaring Brook. This deep, perennial stream flows under the tightly packed diabase rocks in a V-shaped trough or valley of bedrock. On a good day of running water after heavy rains or snow-melt, the stream treats the adventurer to a “roar”, which is where the rocks received their namesake. This brook had no banks so the boulders did not fall into the brook. As a matter of fact, no trees, underbrush or grass exist under the rocks because the stream has carried away all of these. Even though the water has moved smaller rocks in and from the brook, it is not strong enough to move the massive rocks into the positions as they sit now. If you look around the expanded area of the brook, you will find many rocks of the same size or larger. The rocks that are situated over the deep V-cleft were left hanging, in a sense, and the soils beneath them washed away leaving the rocks in their original positions where some slippage and downhill creep have no doubt occurred.
Finally, the answer of how these slabs of rock were formed…weathering. Even though diabase is a very strong material it is still susceptible to the elements over a long period of time. What intensified this weathering came from the cold and frost during the harsh climate of the ice ages, most importantly, the last one, circa 80,000 to 18,000 years ago. This period is where its furthest advance stopped just north of New Brunswick. The boulders, as large as some of them are, have been peeled away, as it were.
How to Claim this Cache:
Answer the following three (3) questions and send them via e-mail to the cache owner. Please do not post your answers so as to give each visitor the enjoyment of visiting and discovering the answers on their own.
Please wait for confirmation before logging your find.
1. The posted coordinates will take you to the bottom of the Roaring Rocks at Roaring Brook, more specifically, a rock that has been dubbed “Table Rock.” Take a measurement of the length of this rock and provide the answer in your e-mail.
2. What visually inherent features of the boulders are the reason they have weathered from extreme cold and frost?
3. Further up from “Table Rock”, what is the approximate distance from the boulders to the water beneath?
It is not required but make sure you post awesome pictures!
How the Sourlands Came to Be
The Sourland Mountain spans an area of four miles wide and seventeen miles long. This area stretches from the Delaware River to just beyond Neshanic, NJ. The “mountain” stands above Neshanic at a height of 568 feet. The mountain top is mostly plateau like and has no obvious or pronounced peaks. Though the height is not as impressive as the Rockies it still classifies as a mountain range.
Sourland Mountain was created during the Triassic Age which lasted roughly 35 million years and ended over 195 million years ago and in the early stages of the Jurassic Period that followed. The early Jurassic Age was busy with enormous volcanic activity. The lava erupted in certain places through sedimentary surfaces and cooled to become basalt rock which forms the Watchung Mountains to the northeast. During this same period, more volcanic activity was occurring beneath the earth’s surface. Magma seeped and spread between sedimentary layers of shale and sandstone forming a vast, so called, “fiery underground lake.” This “lake” would bulge up in certain areas in what geologists called sills (Sourland Mountain is an example of this activity). The magma underneath the surface cooled very slowly becoming diabase or trap rock. The sediments that came in contact with the extreme heat of the magma were literally cooked or baked. Over eons of time, the land became uplifted, tilted and fractured. The top layers of sandstone and shale eroded away which exposed the higher intrusions of diabase and argillite. These rock types erode at a much slower rate. In a nutshell, this is how Sourland Mountain was formed.
REFERENCES
Luce, T.J. (2001). New Jersey’s Sourland Mountain. Hamilton, New Jersey: White Eagle Printing Company
Banino, George M. (1969). Origin of Roaring Brook. Trenton, New Jersey: New Jersey Geological Survey
This cache is certified Central Jersey
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