Just when you thought it was safe to go back in the water…
Not depicted on the Geography page are the rock formations underlying all those soils and topographic features. Several maps are available, including static and interactive ones from various federal and state agencies (key here); the Physical Resources > Bedrock Geology entries in OLIVER are as beautifully rendered as they are revealing to the informed eye.
Local geology remains an active topic for academic research. Even within the past decade, a new map (excerpt shown here) has been in preparation:
Though research is incomplete, and this map still very much an evolving project, one striking feature may be of special interest to area residents and visitors—the Sedge Meadows Fault, passing right beneath Pincushion Island:
While this and intersecting Bloody Bluff Fault do not appear to pose any immediate danger, it is well to consider the living memory of 1940’s Ossipee earthquake and the more consequential 1755 Cape Ann temblor, widely perceived by victims as an act of divine retribution for Boston’s errant ways.
Our own higher standards in both morality and building codes would likely limit damage were such a catastrophe to strike this semi-rural area, though the downtown financial district might not fare so well. However, it is not always seismic shock and sustained shake that cause the greatest damage to persons and property. In the case of Farrar Pond, the relatively well-hydrated high banks of the southeast shore might loosen and slip, displacing most of the water in the pond. This churning tsunami of malodorous meadow mud could rush the length of the pond, shooting across the Sudbury River to wreak havoc at Nashawtuc Country Club and the southern reaches of Nine Acre Corner, even imperiling the hallowed ovens at Verrill Farm.
Various early-warning and other defensive measures are under consideration by responsible parties.