Greenville Mountain Formation
The formation of the Boston area started with the Greenville Mountains. Over 1 billion years ago proto-North America, collided with another continent. The Greenville belt (sediments deposited on the eastern side of proto-North America) was caught in between the colliding continents and was thrust upon the side of proto-North America. The continental-continental convergence that resulted formed the Greenville Mountains. They stretched from Canada to Mexico and ran through what is now western Massachusetts ("Mountain Building Part I: The Grenville Mountains"). The Greenville Mountains were then pushed into Baltica (another early continent), forcing the crust to fold into mountains. As soon as they formed, they began to wear down due to weathering and erosion,
Formation of Avalon Island Chain
Around 570 million years ago, there was a subduction zone along the edge of the ancient continent of Gondwana in the far Southern hemisphere. There was a lot of volcanic activity, due to the subduction zones. This led to the formation of the volcanic Avalon mountain chain. Rifting occurred along the edge of Gondwana. Within the Avalon area major faults and rift valleys formed. This includes what we know now as the Boston Rift Basin. Around 550 million years ago, Avalon and other micro-continents separated from Gondwana and drifted North-West. At that point, Avalon was an island arc (Boston Geology) and most of the world's land masses were south of the equator. At about 540 million years ago both Laurentia (proto-North America) and Baltica (proto-Western Europe) drifted away from Gondwana (Boston Geology).
Pangaea
Avalon then collided with early North America about 380 million years ago during the Early Devonian period.
Eventually, all the continents came together and formed the supercontinent of Pangaea about 250 million years ago (Boston Geology). Avalon was then smooshed between Baltica and Africa on one side, and North America on the other side forming the Appalachian Mountains.
Breakup of Pangaea
Pangaea then broke apart 200 million years ago (Boston Geology). As it was breaking, many rift valleys formed. Rifting stopped quickly. The only rift still continuing on was the mid-Atlantic Rift Zone. Rifting caused valleys to form. Also, some lava flow was able to seep through the cracks to the surface. That is why one can see igneous rocks in Eastern Massachusetts.
After the initial breakup of Pangaea, the eastern North American plate boundary ended up well offshore of North America, at the mid-Atlantic Ridge out in the middle of the ocean (Boston Geology). Slowly, volcanic activity began to cease and the continents began their movement towards their present locations.
From then on, Boston’s geologic history became one of weathering, erosion, deposition (glacial activity). Rivers ran from the volcanic rock formations surrounding the Boston Basin, leaving deep channels in the softer sedimentary rocks, especially the Cambridge Argillite (Boston Geology).
After the initial breakup of Pangaea, the eastern North American plate boundary ended up well offshore of North America, at the mid-Atlantic Ridge out in the middle of the ocean (Boston Geology). Slowly, volcanic activity began to cease and the continents began their movement towards their present locations.
From then on, Boston’s geologic history became one of weathering, erosion, deposition (glacial activity). Rivers ran from the volcanic rock formations surrounding the Boston Basin, leaving deep channels in the softer sedimentary rocks, especially the Cambridge Argillite (Boston Geology).
In the geological past, Massachusetts has been the location of many continental collisions and collisions with other micro-continents and volcanic arcs, with their resulting mountain-building events. As a result, the state rock structure is squeezed together.
Here is a video about Earth's Geological Activity: