[Grant]

The Ossipees are actually the world's most famous example of what geologists call "ring-dike formation."

As for how Rattlesnake avoided being razed by the glacier, if you look at the area from the perspective of the map above, and consider all the tectonic upheaval and the movement of the glacier, you can see that much of it was "gouged" out. Rattlesnake, is geologically, is actually part of the Belknap Mtns. The Lake botton in that area plunges precipitously -- the deepest part of the Lake is not far off the northern end of the island...and much of the lake's underwater topography mirrors that of the surrounding area -- glacial eratics (the random boulders found all over the state), rock walls, outcroppings, hills, etc.