How Was The Grand Canyon Formed?

Could you tell me if this essay is good enough:
The canyon was created by the action of the Colorado River over about 6 million years of erosion. The Colorado River basin has developed in the past 40 million years and the Grand Canyon itself is probably less than 6 million years old. The formation of the Grand Canyon was accomplished by the constant erosion of the rock by the Colorado River over some 17 million years. Over time the river was able to carve a very deep channel into the Colorado Plateau. The rock layers in the Grand Canyon range from 250 million to about 2 billion years old.
The exact reasons for creation of this astounding canyon are not known. Of course, there are many assumptions and theories. The erosive activity of the Colorado River is thought to be the prime cause for formation of the Grand Canyon. Certain other forces, like change in the Colorado River course, volcanism, continental drift, and the Earth’s orbit.
The formation of the Grand Canyon, the area was believed to be occupied by a chain of mountain ranges. These mountains, after a span of millions of years, had become plain due to erosion activities of water, ice, and wind. Meanwhile, due to the sudden climatic changes, the oceans moved over these areas and deposited rock layers. This process was repeated, resulting in the deposition of several rock layers. At times, the interval between two consecutive depositions was so fast that the upper layer usually got eroded completely by natural forces before the second layer was deposited.
At this point of time, the ancestral Colorado River came into existence about 70 million years ago. In those times, the course of the river was subject to changes, mainly due to alteration in the surrounding terrain. The tributaries of the Colorado River also contributed to the erosion process. Then, about 16 -17 million years ago, the Colorado Plateau was uplifted due to pressure from underneath the Earth’s crust and movement of the tectonic plates.
The rise in the elevation from the sea level prevented the submersion of these areas by the seas. On the other hand, the Colorado River continued to erode the canyon sides. Apart from the erosive activity of the Colorado River, the debris flow played a major role in the widening and deepening of the Grand Canyon.
All these factors contributed to the formation of the Grand Canyon, which remains an intriguing feature for every one of us and especially for the geologists. The rock layers, as we have seen, are actually formed due to depositions by the oceans and seas. This is evident from the fact that rocks found on the sides of the canyon are mostly of sedimentary type. Scientific said that erosion is how the Grand Canyon was form.
Please correct me if I’m wrong and change some of the words to a 7th grader word.