Geology of Massachusetts

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The geology of Massachusetts includes numerous units of volcanic, intrusive igneous, metamorphic and sedimentary rocks formed within the last 1.2 billion years. The oldest formations are gneiss rocks in the Berkshires, which were metamorphosed from older rocks during the Proterozoic Grenville orogeny as the proto-North American continent Laurentia collided against proto-South America. Throughout the Paleozoic, overlapping the rapid diversification of multi-cellular life, a series of six island arcs collided with the Laurentian continental margin. Also termed continental terranes, these sections of continental rock typically formed offshore or onshore of the proto-African continent Gondwana and in many cases had experienced volcanic events and faulting before joining the Laurentian continent. These sequential collisions metamorphosed new rocks from sediments, created uplands and faults and resulted in widespread volcanic activity. Simultaneously, the collisions raised the Appalachian Mountains to the height of the current day Himalayas.

Warped and faulted basins formed in eastern Massachusetts and preserve coal from massive Paleozoic swamps as well as fossil plants and insects. The final phases of mountain building occurred as Laurentia completed its collision with Gondwana and Europe to form the supercontinent Pangea. Beginning around 200 million years ago, rifting broke apart Pangea. Erupting basalt lavas formed the new oceanic crust of the Atlantic Ocean, wedging apart Africa, Europe and North America along the approximate lines where the continents collided. The Connecticut River Valley and the Middleton Basin formed as failed rifts, filling with sediment that preserve dinosaur footprints. After the Jurassic, Massachusetts experienced long-running and continuous erosion with no more volcanic activity and only low-level seismic activity. The Appalachians shed sediments eastward, accumulating as the Atlantic coastal plain of southeastern Massachusetts.

A rapid cooling of the planet in the last 2.5 million years of the Quaternary resulted in one-mile thick ice sheets advancing southward and accelerating erosion. The Pleistocene glaciations rechanneled rivers and created large sediments deposits, including the terminal moraines of Cape Cod, Martha's Vineyard and Nantucket, as well as hundreds of smaller drumlins, eskers and kame deposits.

Today, universities in Massachusetts are hubs for worldwide geologic research while local professional and amateur geologists study landforms and geologic history, applying knowledge of regional geology to construction, environmental remediation, water resource management and quarrying.