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Geology of Massachusetts
The geology of Massachusetts is the result of a process that began over a billion years ago. Massachusetts currently lies at an edge of a continent, and in the geological past has been the location of many continental collisions and collisions with other microcontinents and volcanic arcs, with their resulting mountain-building events. As a result, the state rock structure is squeezed together. Recently, multiple Ice Ages have shaped the modern geology of the state and have created notable landmarks such as Cape Cod.
==Early history==
The early history of Massachusetts can be traced to around 1.2 to 1.1 billion years ago in the Mesoproterozoic Era. Ancient areas of continental crust or cratons formed the nuclei of continents. The ancient continent Rodinia was formed as a byproduct of the collisions of earlier cratonic fragments. Mountains were formed during the Grenville orogeny. Some of the rocks of the Berkshire highlands are from this era.〔 - Total pages: 379〕〔
Around 750 million years ago, Rodinia began to break up and the Laurentian craton was formed. Two hundred million years later, Gondwana was formed. Laurentia increased in size because of the addition of Japan-sized islands. It is possible that the Merrimack, Nashoba, Avalon, and Meguma terranes that make up eastern Massachusetts are remnants of these island arcs or microcontinents. It is highly likely that these terranes broke off from Gondwana at some point in their history and collided with Laurentia, between 550 and 370 million years ago. These resulting collisions were part of the Taconic orogeny. The Iapetus Ocean, separating the two continents began to open up when Rodinia broke apart. The size of the ocean eventually prevented migrations between the two landmasses.〔〔
Between 425 and 370 million years ago, the two continents began to collide, forming Pangea. During this time, the Acadian orogeny, which marked the collision of the two continents, occurred. Around 200 million years ago, Pangea began to break apart. This caused rift valleys to form within the interior of the continent. One of these rift valleys, the Connecticut River Valley is a failed rift of the continent. Basalt dikes present in the underlying rocks of the valleys are the result of volcanism.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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