Large rooms are created by a combination of the processes mentioned above and other factors – type of limestone, bedding-plane and fissure placement, water volume and rate of flow, etc. Oh, yes. And collapse. Didn’t I mention that? Sure, with the walls getting further and further apart in a flat-roofed chamber, with millions of tons of Mama Earth weighing down and no support beneath to relieve the strain, the ceilings are bound to fall in, leaving an enormous pile of rocks that cavers call breakdown.
Collapse continues until the ceiling assumes a stable dome or arch conformation. If the collapse occurs in a chamber close to the surface, however, the absence or near-absence of limestone (or anything) beneath the topsoil causes a “sinkhole” to appear on the surface. Sinkholes very often prove to be cave entrances. But watch that first step.
But come, why have I told you in such pedantic detail about the origins of caves. So I can tell you this. You’re in tough shape for real caves if you live in Massachusetts. Better shape than if you lived in New Hampshire or Maine, but still tough. The reason is this. You could take all the limestone that’s east of the Green Mountains, place it on your desk, and it might hold the telephone bills down if the breeze isn’t too strong. In the formation of the peneplain upon which the topsoil we revere as Massachusetts resides, the long gradual slope from the Berkshires to the sea, the limestone was washed off. After the mountain chains arose and gave a new slant to things, the limestone was scrubbed off just like that, quicker than you could say the nine billion names of the Almighty, right down to the hard insoluble rock that was formerly the ocean floor. (They said it was gneiss, but we took it for granite.) Even west of the mountains, cave prospects aren’t much. The upthrust of the ranges made accordion pleats out of the limestone immediately to the west and caves formed in the folds. Then the glaciers came highballing through and scrunched it all flat, collapsing all but the lowest level of cave. The result is, you find a fair number of limestone caves in western Massachusetts, but they’re not very extensive. The picture brightens as you continue westward into upstate New York — where, not incidentally, the commercial cave zone begins.
For those of you who wouldn’t know a cave from a hole in the ground, let us distinguish at this point between two types of caves in terms of caving experience: commercial and wild. Commercial caves are developed, with admission fees, walkways, handrails, boat rides, spectacular speleothem displays, electric lights, and no mud. Sometimes they have restaurants and ballrooms, even. And inevitably, guides who switch on a row of lights and direct your attention to rock formations that resemble other things. It’s called gilding the lily. By unwritten law, every single rock in a cave has to look like something else. A pile of rocks cannot be interesting or majestic simply because it resides in the Plutonian depths. No, it has to present the perfect silhouette of three Indians and a Brontosaurus playing badminton when lit from behind. Or Abraham Lincoln kissing Martha Washington. In which case it’s called something cretinous, like the Pet Rock. One’s only consolation is in knowing that when the rocks cease to be American historical figures in anachronistic adultery and revert to being semi-eternal rocks, surface water will percolate through that guide’s moldering dust, gathering carbon dioxide, and add something of beauty to an underground chamber.