|Era||Period||Million Years before present||Events|
Most recent period of Ice Ages begins 80,000 years ago. Last Ice sheets retreat around 14,000 years ago.
Medford Gabbro forms - 190 million years ago
Pangaea begins to break apart. Atlantic Ocean begins to open.
|Triassic||245||Map of the Earth ~237 million years ago (Early Triassic)|
Pangaea assembled. Mass Extinction where well over 90% of all life became extinct!
Weathering and erosion of mountains form Pondville Conglomerate
Nashoba and Avalon collide with Laurentia - "Acadian Mountain building event". Bloody Bluff Fault Zone is created between Nashoba and Avalon
Rifts in Avalon continue, continuing formation of granites.
Eruption of Blue Hills Volcano - 440 million years ago
Avalon terrane pushes into Nashoba terrane, forming a subduction zone. Additional mylonites form between the two terranes - 443 to 417 million years ago
Nahant Gabbro forms
Formation of Quincy, Franklin, Cape Ann and Peabody granites as rifts open in Avalon.
|Cambrian||545||Map of the Earth ~514 million years ago (Late Cambrian)|
Avalon separates from Gondwana - 550 million years ago
Roxbury Conglomerate, Cambridge Sandstones and Slates form in Avalon. Mountain-top glaciers erode mountains to form Squantum Tillite - between 570 and 550 million years ago
Lynn and Brighton volcanics form in Avalon - between 570 and 550 million years ago
Boston Rift Basin forms in Avalon - 570 million years ago
Burlington Mylonite Zone forms ~600 million years ago
Avalon microcontinent forms