Friday, November 10, 2023

Geology of the National Parks in Pictures - Great Smoky Mountains National Park

My next post about the Geology of the National Parks Through Pictures is from even further back to my undergraduate days when we traveled the east coast hitting up National Parks.  

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


Way back in 2003, we visited the Great Smoky Mountains and camped out in the park, as we traversed the eastern states. 

Obligatory entrance sign shot. The history of the Great Smoky Mountains begins long ago.

Prior to the formation of the supercontinent Pangea, there were other supercontinents, one of which was named Rodinia. It was during the continental collisions that formed Rodinia (around 1.3 to 1.0 billion years ago) that much of the bedrock of the Great Smoky Mountains was formed due to the incredible compressional forces. During this time many of the sedimentary rocks that had previously been deposited were turned into the over billion year old metamorphic and igneous rocks that forms the core of the park. These rocks can be found outcropping in the southeastern parts of the park. 

The supercontinent Rodinia. Image courtesy of Public Water

During the formation of Rodinia, the Great Smoky Mountains were located between the North America continent (known as Laurentia) and the Amazonia continent (seen above in the orange stripe). These proto-Great Smokys were formed during the mountain building event known as the Grenville Orogeny. Rodinia then started to break up around 750 million years ago.  

Following the break up of Rodina, a wide sea opened up between what will become North America and Africa. This was known as the Ocoee Basin and was formed near present-day western Carolinas, eastern Tennessee, and northern Georgia, where the Great Smokies sit today. Within this ocean basin sedimentary rocks started to be formed. These sandstones, shales, limestones, and other sedimentary rocks formed a huge group of rocks known as the Ocoee Supergroup. More sedimentary rocks were then deposited on top, including large amounts of limestones filled with fossils of crustaceans and worm burrow trace fossils.

Following the deposition of the sedimentary rocks, the continents took an about face and started to head back towards each other once again about 470 million years ago to create another super continental "bounce". This time the eastern edge of North America once again crashed into Africa, forming Pangea 310 to 245 million years ago. It was during this collision that the Great Smoky Mountains, or at least the massive mountains they originated as, were formed, along with most of the Appalachian mountains along the eastern coast of North America. These mountains were said to be even bigger than the present day Rocky Mountains. 

Around 240 million years ago, Pangea began to break apart, continuing the continental bounce, eventually forming the Atlantic Ocean. During this time, the erosion of the Great Smoky Mountains continued, depositing sediment from the mountains off the coasts towards the Gulf of Mexico and the Atlantic Ocean basins. Over time, erosion greatly reduced the mountains from the once giants that had filled the area, producing the mountains as we see them today. 


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