This series of slides illustrates the plate tectonic assembly of Connecticut.

Click on the image for a larger view

RalphsSlide10.jpg (54285 bytes) To understand how the various rocks of Connecticut came to be assembled, we need to take a global view.
RalphsSlide11.jpg (41082 bytes) The outer, rigid shell of the earth is broken into large, irregular plates, which move around only slightly faster than your fingernails grow.  This where they are today -- note that Connecticut is in the eastern North American plate and west of the Eurasian and African plates. In various places, the plates move apart, together, or side-by-side.
RalphsSlide12.jpg (40235 bytes) 500 million years ago, the plates were arranged something like this.  Instead of the modern Atlantic Ocean, we had the Iapetus Ocean to the east of what is now Connecticut.  In Greek mythology, Iapetus was the father of Atlantis, thus the name. The bar connects similar points in this and the following slides.
RalphsSlide13.jpg (39873 bytes) The plates slowly collided one by one, finally forming a super-continent called Pangaea (meaning "all one Earth") not long before the beginning of Mesozoic time.  The collision between proto-North America and Proto-Africa (possibly with a couple of smaller plates as well) wrinkled the earth to form the Appalachian Mountains.  Most of New England is within this mountain chain.
RalphsSlide14.jpg (40902 bytes) Again, here is the arrangement of the continents today.  Connecticut was involved in the events that rifted Pangaea apart to open the Atlantic Ocean and create this modern pattern, starting 200 million years ago.
RalphsSlide17.jpg (59473 bytes) New England today shows regions that had different geological origins, which are pieces of the ancient plates that collided and fused together.  Several un-labeled pieces, called terranes, actually constitute the Iapetus group, much of which was in the ancient ocean. Avalonia was left behind when Africa separated from eastern North America, which opened the present Atlantic Ocean.  The "Newark" terrane was also created by that event; it and others like it are named for a similar piece in New Jersey.
Next page: the rift zone
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