Lemon Slice Nebula

Lemon Slice Nebula
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Wednesday, July 30, 2014

Past Lives of the Grand Canyon

A brief preface: I was never really inspired to understand what the Grand Canyon was. I was honestly a bit afraid and overwhelmed by the potential learning I could gain from it. So when I had the opportunity a couple of weeks ago to venture out into the canyon myself, I just had to continue searching until I could grasp a greater understanding. 

The history of the last 2 billion years contained and displayed in a single, incredible location was more than ample inspiration to develop a "need" to know. This experience is one that will always stick with me for my blip of existence on a vast timeline in an infinite (maybe?) universe.

The landscape of the Grand Canyon has changed drastically and often, at least relative to we might assume. Throughout the layers of rock found there geologists postulate that the rock formations there have been submerged in an ocean 8 different times over the last billion years. And before that? The oldest rocks in the grand canyon, nearly 2 billions years old and commonly referred to as black rocks, were once at the base of a mountain range 5 miles high. The immense pressure from mountains actually formed garnet in these molten-looking rocks. The last time the rock layers of the grand canyon were under the sea was around 80 million years ago.

Each of these instances of being submerged in the sea brought with it not only different forms of life along the evolutionary tree but also various types of sediment. For example the layers of sand pressed down over millions of years formed into sandstone. Others contained mud that compressed into dark shale. Then when higher ocean life forms, like crustaceans, were crushed in with sediment, limestone was formed.

However, found throughout every layer is contained massive amounts of iron, which has oxidized and is now credited with coloring most of the canyon with the most prominent color of red.

Before most of what we see now at the Grand Canyon and even before North America had split adrift to its current location, our continent endured a major and violent clash. About 1700 million years ago, during the Precambrian Time, a string of island volcanoes, very similar to what we find today in places like Hawaii, was developing and on the move.

 As North America began to break away, it was headed on a collision course with these volcanic goliaths. As the two crashed into one another, the volcanic formations suddenly began to metamorphize with the rocky surface of the North American continental crust. This massive collision of land mass was then forced to a much higher altitude. Now, all of the rock layers that had been deep in the now Pacific ocean were pushed up about a mile above sea level to their current altitude.

Now, fast forward to only 5.5 million years ago. the Colorado River begins to form and flow. According to a theory formulated by geologist John Douglass, the river flowed and then pooled into an area, which is now referred to a Lake Bidahochi. This lake was larger than Lake Michigan in size and spanned over 20,000 square miles. This lake butted right up against the raised plateau of rock raised from the collision. 

The force of the water still pouring into the lake pushed until it began to pour up onto the plateau. It was this incredible outpouring of an expansive lake, and not just a river that carved what we see today.

Even with the massive power of the overflow over the plateau the incredible rate at which the canyon was carved was about 1 inch every century. Now amplify that in your mind and imagine the sediment, rocks, and boulders being carried by the outpouring of water inch by inch, leading into 1,000 feet per million years. Picture a prolific waterfall with immense force slowly moving back little by little until it has cut down the expanse of the large plateau.

 Even today the Colorado River carries 5 tons of rock and debris through the canyon every second. This effect is compounded by erosion on the canyon through rain, falling rocks, and layers of different density being exposed to the elements. For example muddy layers of shale are quite low in altitude in the canyon but are most easily affected by weather. So as rocks erode and fall into the river it is carried through the canyon allowing in to continue to widen just as rapidly.

National Park Service
Grand Canyon: How It Was Made (Youtube)

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