Friday, October 17, 2008
The islands in Boston Harbor are glacial knobs and drumlins, formed of outwash and shaped by the ice. At one time, this must have been paradise for eccentrics who sought out eroding bluffs and gravel beaches and the more exotic classes of barrier landforms. It probably still is if your eccentric has a boat, a good map, and a stomach for granite revetments. The revetments are both elegant and extensive, transforming miles and miles of outwash bluffs and mixed sand and gravel beaches to monotonous cliffs of paleozoic gneiss. Don't get me wrong - if you're going to bury a beach under big rock, it is far better to use use nice rock and stack it carefully than to dump poor quality stuff in pile of rubble! Looks better, lasts longer, is easier to walk across.
Deer Island is another island wannabee - partly connected by tombolo to the mainland (or at least to Winthrop) although at some point historically there was a cut (or gut, locally) between them (in this case, Shirley Gut, which later became Yizzell Beach). Deer Island is the site of a major sewage treatment facility - apparently a centerpiece of the effort to clean up Boston Harbor - and is surrounded by a park and trails. And oh, did I mention, lots of rock.
But there are gravel beaches, too. In several places, the configuration of the shoreline allows for pocket beaches. Some of the pockets are deeper than others, but they go to show that beaches are perfectly possible, even where wave energy is high. Here they collected mussel shell and provided a nice place to get down to the water.