Ever heard of the Mysterious Ringing Rocks of Pennsylvania? Apparently, it is not uncommon for visitors to this park to show up with hammers to bang on rocks.
I stumbled upon this interesting phenomena in a book I just bought… The Book of Useless Information No, I’m not kidding, see for yourself! And while you are there, if you want to buy it, at the time of publication it is on sale and has a $5 off coupon making it less than $5!
Where to find them.
I have never heard of these rocks … but I am planning a trip to Southeastern Pennsylvania to check these out for myself and make a homeschool road trip out of it! When we visit, we will find a boulder field in the 123-acre Ringing Rocks Park. This park is surrounded by a lush forest and has a beautiful waterfall too! So it will be a fun and beautiful road trip! But they are not limited to just this park! Southeastern Pennsylvania has many sites where rocks ring when struck by a hammer: Stony Garden in Haycock, Bucks County. Devil’s Race Course is in Franklin County. But the one that is most well known and studied is at Upper Black Eddy in Bucks County. It is a mile west of the Delaware River near the New Jersey state line. If you go visit Ringing Rock Park, be sure to spend a few extra hours and visit Falling Water, the most famous house designed by Frank Lloyd Wright!
Why do they ring?
These rocks look no different than any other rocks. The boulder field is barren of vegetation except lichen and is ten feet deep and seven acres around and some are stacked as high as ten feet. These ringing rocks (also known as sonorous rocks) are composed of igneous diabase (also known as dolerite and diorite – that will sound familiar with Minecraft fans) and they don’t usually ring. There are a number of theories out there about why they ring (or don’t). In 1965 geologist Richard Faas of Lafayette College, Easton, Pennsylvania, conducted laboratory experiments on them. He learned that when he struck a ringing rock, a series of sub-audible frequencies were produced, and these added up to a tone that could be heard by the human ear. However, he could not determine a specific physical cause. And what is even more weird, not all of the Ringing Rocks ring. Apparently only about 30 percent of them.
In June 1890 Dr. J. J. Ott played a few selections on the rocks for an appreciative Buckwarnpurn Historical Society gathering. He even had a brass band accompany him. Ott assembled the rocks of different pitches to create an octave scale… moving them confirmed that the rocks don’t have to be in their natural location to ring. They do not even have to be intact. We don’t have a video of that performance, but this one is pretty good!
The rocks sound different based on temperatures, it changes their pitch! So they will sound different if you visit them in the winter versus the summer!
Have you ever visited or heard ringing rocks? Leave us a comment and tell us where!