Materials for this Earthcache:
History of the Parsippany Rock House:
Known to generations of local school kids as the Rock House, the Parsippany Rock Shelter is a collection of titanic glacial boulders that tumbled to form a rudimentary shelter. Evidence of human habitation extends as far 1250 BC, and as recently as the late 1500s by the Lenne Lenape. Although there's no conclusive evidence for the location as a calendar site, it may have had astronomical significance in prehistory. The landmark contains a rare New Jersey example of Native American petroglyphs, thought to have been etched into the rock between 500 BC and 500 AD. Care has been taken to isolate and protect the glyphs, which depict animals and human figures, for future study and scholarship.
What is a glacial erratic?
A glacial erratic is a glacially-deposited rock differing from the size and type of rock native to the area in which it rests. Erratics take their name from the Latin word errare (to wander), and are carried by glacial ice, often over distances of hundreds of kilometers. Erratics can range in size from pebbles to large boulders. They are indicators that mark the path of prehistoric glacier movement. Their lithographic origin can be traced to the parent bedrock, allowing for confirmation of the ice flow route.
What is a Glacial Striation?
Glacial striations are scratches or gouges cut into bedrock by glacial abrasion. Abrasion occurs when a part of a glacier wears away at rock. Glacial striations are usually multiple, straight, and parallel, representing the movement of the glacier using rock fragments and sand grains, embedded in the base of the glacier, as cutting tools. Large amounts of coarse gravel and boulders carried along underneath the glacier provide the abrasive power to cut trough-like glacial grooves. Finer sediments also in the base of the moving glacier further scour and polish the bedrock surface. Ice itself is not a hard enough material to change the shape of rock but because the ice has rock embedded in the basal surface it can effectively abrade the bedrock. Most glacial striations were exposed by the retreat of glaciers since the Last Glacial Maximum or the more recent Little Ice Age.
What is a chatter mark?
Chatter marks are small, curved fractures found on glaciated rock surfaces. Chatter marks are commonly 1–5 centimeters (1/2–2 inches) but might be submicroscopic or as much as 50 cm in length. They occur mainly on hard, brittle rocks such as granite and are formed under a glacier by the pressure and impact of boulders moved along by irregular rolling or sliding.
Logging Tasks:
1. Examine the rock formation at the GZ. Is this considered to be a glacial erratic? If so, why? Estimate the average height of these boulders.
2a. Look at the glacial striations on these rocks. Do they seem to be facing the same direction?
2b. Now, take a look at the size and width of the striations. Are they about:
3. Are there any visible chatter marks on any of the rocks in this formation?
4. (most importantly) Enjoy your visit and have fun!
5. As of June 2019, earthcaches are now allowed to have a required photo logging task. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
**Don't forget to check out BrianSnat's nearby Rock, Stock, and Barrel geocache!
Confirm your find by answering these questions on this Google Form or by sending your answers to us via message center.
Congrats to chrmdome and NJ-Trekker for the FTF!
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Sources:
https://en.wikipedia.org/wiki/Glacial_erratic#Glacier-borne_erratic
https://www.njskylands.com/tn_parsippany_091
https://en.wikipedia.org/wiki/Abrasion_(geology)
https://www.britannica.com/science/chatter-mark
Check out Our Other NJ Earthcaches!
Asbury Park's Beach Erosion Crisis
Seawalls in Wildwood
Wildwood's Shoals
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