Massachusetts ROCKS!


APES‑ F


Geology


120,000 years ago ice began to form at a rapid pace in northern Canada(Grette, www.biomass.umass.edu). This sheet quickly (on a geologic scale) swept down the eastern seaboard and engulfed the northeast down to present day Long Island, New York in a sheet of solid ice. This ice‑sheet later in history became known as the Laurentide ice‑sheet, named after the region in Canada in which it made its descent(Oldale, http://pubs.usgs.gov). Little did anything know back then that it would have had such a profound impact on a region as it did on the northeast.


Particularly in Massachusetts’ case we owe the ice‑sheet for giving it the distinctive "flexed armed" appearance we see with Cape Cod jutting out into the Atlantic Ocean. This formation was created by the active Laurentide sheet approximately 14,000 years ago(Pinet, 1992). The advancing ice‑sheet brought and pushed sediment that has created the Cape Cod peninsula. This glaciation of the area brought huge boulders and rocks down from Canada on its descent, and ground up native rocks and gravel to sand and sediment. After reaching its furthest extent about 10,000 years ago, and has long began its retreat. It had left behind all the rocks, sediment, and debris locked in its frozen vaults. After it had completely left the area, behind it was the recessional moraine, Glacial Cape Cod Lake. As the glacier fully receded water levels rose, filling in an area of about 3 miles of shore once a part of Massachusetts, and consequently filling in the glacial lake.


Resulting from the receding Laurentide Ice‑sheet, many new minerals and rocks were deposited on the area that have never been seen here before. The bedrock was formed in the late Precambrian and Paleozoic eras, and is made up of crystalline igneous and metamorphic rocks. So, these have been here all along. Glaciers in the Pleistocene and Holocene eras, deposited many sedimentary(eastern Mass.), igneous(middle/eastern Mass.), and metamorphic rocks(eastern/middle Mass.) throughout the state.


These deposits (most prevalent sedimentary) are found along the coast of eastern Massachusetts and makes up the entire arm of Cape Cod. This may not seem like such a big deal, however the Till made of Pleistocene and Holocene sediments is a very loose and grainy type. Though this sediment helps make the Cape a wonderful beach area, it may lead to its demise as well. In some areas of the Cape may erode bluffs 10‑15 feet in a 2‑7 period of time(www.whoi.edu). Many of these problems have been magnified my human occupation and alteration of the shoreline.


Today, the innovative species we are, have taken this material brought to us on a proverbial flying carpet and made a business out of it. Many of the rocks mined throughout Massachusetts are used as building materials, gravel, and sand. Though this may seem petty, it is a very lucrative business and the state makes a lot of many though exporting natural minerals and rocks.


In the state of Massachusetts mineral, stone, and steel exports make the state over a one hundred‑million dollars annually and employ thousands of workers in mines, processing plants, and excavation. On the states list of the top 97 exports six of them involve the geology of the state directly while others also are connected, yet indirectly. On that list ranks base metals(23), aluminum(26), stone for art purposes(38), copper(39), salt and sulfur(61), and mineral fuel(67).


Ancient Massachusetts was a very different place than it is today. Once covered by a huge glacier only 13,000 years ago, now has one of the most recognizable coastlines on the eastern seaboard. Massachusetts has truly been molded by the glaciation of the past. What remains of that giant sheet now helps our economy run(somewhat) smoothly, our citizens to enjoy the beaches, and a distinctive land formation, that is Cape Cod.