Rocks, stones and erratics: the 'bedrock' of life

Mon, 04/11/2011 - 3:51pm
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Rocks, stones and erratics: the “bedrock” of life

Garnet, quartz, mica, pyrite – stones, rocks, erratic boulders: the substrate upon which all Block Island life exists. Block Island’s geology offers several allegories. As a terminal moraine (a debris field of materials relocated here by moving and melted glaciers) the physical island has no native stock. Everything has landed here from away. And, the mix of materials is highly diverse. Some rocks and boulders were ripped from bedrock as far away as Iceland and Great Britain, other stones are from the shales and slates of northern New England. Some materials have their origin in the process of erosion, while others are the result of heat and pressure-driven metamorphosis.

The geology of Block Island is full of large-scale complex physical processes described with terminology and vocabulary worthy of being classified as a distinct dialect or lexicon, separate from everyday speech — if not actually a foreign language. Just as it is not necessary to understand the physics of how a hammer works (acceleration, impact, arc, leverage) to appreciate the wonder of a hammer’s work, one does not need to have a working knowledge of geology to appreciate the variety, the beauty and the importance of rocks, stones and erratics in supporting live on Block Island.

Although there are any number of starting points to consider, there are two obvious locations where the presence of rocks meets the inquisitive and creative minds of Block Island walkers. Inland rough-hewn stonewalls, and the surf-tumbled-smooth mounds and benches of cobbles showing at the island’s edge like a frilly petticoat. Though completely different in look, these two assemblages of stones and rocks share commonalities. Again, all stones (buried in the earth, balanced in rows, perched in bluffs or in jumbled piles at the shoreline) were deposited here from other locations. Stone walls and cobble beaches function as boundaries, first lines of defense from ravaging surf or marauding livestock; and in each case, a single rock or boulder will not a stonewall or beach strand make. Rock walls and cobble shoreline benches depend on the wedging together of many, with enough space to allow the power of wind and wave to dissipate and to absorb their energy — a shoulder to shoulder bracing for the common good.

Each community of stones — basically comprised of the same assortment of minerals — provides for a multifaceted island whole. Lift a lichen-covered capstone from a stonewall and one may find spider threads, cottony cocoons and scurrying insects. Roll an earthbound stone fallen from a wall and one may find beetles, worms and pale fungi. Tip over a barnacle-covered cobble and crabs, snails and seaweed will be found clinging or scattering.

Think of it, non-living rocks and minerals of all sorts, deposited here from afar, have provided not only a physical armature for our island community, but they are also the materials, which through chemical and physical processes, are transmogrified into life as diverse as non-photosynthetic fungi, symbiotic lichens, filter-feeding barnacles and net-building spiders.

There is much to admire about the island’s rocks, stones, boulders, cobbles, conglomerates of Pots-and-Kettles, etc. But one need not master the lingo or know the difference between the rock-forming minerals quartz, mica, granite or garnet to appreciate their beauty or to recognize their importance.

The following April events and Ocean View Foundation's programs are sure to provide opportunities to observe the relationship between the island’s rocks and stones and its living organisms.

April: note the graying and greening of stonewalls as their lichen patches thrive in spring’s moisture.

Likewise, salt-sprayed boulders at the shoreline will green up with the season’s new life of algae.

April 5 and 19, at 8 a.m.: Crazy-as-a-Coot Bird Walk, call 595-7055 for location.

April 9 at 7 p.m.: A showing of the films "Fresh" and "BI Wind" at the Island Free Library.

April 21: Earth Day Scavenger Hunt, time and place to be announced.

April 22 (Earth Day), at 8 p.m.: Twilight Walk & Night Sky Viewing, Hodge Preserve.

April 29: National Arbor Day