The result was the creation of the beautiful
Appalachian mountains; and because they aren't so very old yet,
they still are there, and inspire us with their beauty. Iapetus
was "closed" (in science speak), or crunched together
(in the vernacular) between about 475 to 275 Ma, in other words
it took a while, 200 Ma. How come?
It was a big job and took a series of separate orogenies (or mountain
building episodes) until what had come in between the former borderlands
of the ocean had been swept up, and the converging continents eventually
came to rest against each other.
For the record, these events were the Mid-Ordovician Taconian Orogeny
(around ~475 Ma), the Silurian Salinic Orogeny (~420 Ma), the Devonian
Acadian Orogeny (~380 Ma), and, finally, the Permo-Carboniferous
Alleghenian Orogeny (~280 Ma). Let's place these geological age
names into their proper slots on our geological time scale.
All of the times mentioned above, the Cambrian, Ordovician, Silurian,
Devonian, Carboniferous, and Permian (from oldest to youngest) belong
to the Paleozoic. The Paleozoic, in turn, is the oldest chapter
of the Phanerozoic, which followed the Precambrian (all of what
had gone before it). The Precambrian had seen the completion of
the Canadian Shield with the addition of the Grenville Orogen. We
now are firmly in the Phanerozoic, and soon will turn to the youngest
orogeny, added on to the west in Mesozoic times. And, as we have
known from the beginning of all this, this adding on to the west
coast still is continuing today, when we are in the Quaternary,
part of the Cenozoic. Have one more look at the geological time
scale, before we switch one slide BACK again, to
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