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.
Geological History
Proterozoic (1.2 billion–539 million years ago)
The early history of Massachusetts can be traced to around 1.2 to 1.1 billion years ago in the Mesoproterozoic Era of the Precambrian with some of the oldest rocks in the state situated in the Berkshires. What is now the western edge of the state was at the time the continental margin of the proto-North American continent Laurentia. The Grenville orogeny significantly altered many rocks through metamorphism as Laurentia collided with the Rio de la Plata Craton and Amazonian Craton to form the supercontinent Rodinia. In fact, the Berkshires are dominated by gneiss that metamorphosed during the Grenville orogeny.
The Rodinian continent broke up around 750 million years ago and rocks of proto-Massachusetts may have bordered the current west coast of South America in the west of the short-lived Pannotia supercontinent. Africa, South America, Australia, India and Antarctica formed the new continent Gondwana while Laurentia and Baltica drifted away as separate continents throughout the rest of the Proterozoic. Africa, South America, Australia, India and Antarctica formed the new continent Gondwana while Laurentia and Baltica drifted away as separate continents throughout the rest of the Proterozoic.
In the late Proterozoic, a series of small island arcs began to form offshore of Gondwana while continental crust developed as part of the Gondwanan continent, before splitting off as microcontinents and other small continental terranes. For example, the Nashoba terrane formed as a mid-ocean island arc and is now wedged between the Merrimack and Avalon terranes, bounded by the Clinton-Newbury fault in the west. It extends south to Chester, Connecticut and Long Island Sound.