The Grand Canyon shows secrets of how the Earth's geology evolved . Geology is the study of how earth, rocks, volcanoes, plate techtonics and water shape the Earth. In the first video you see the big Colorado River. The big Colorado River is 1,400 miles long. For 277 miles of the 1,400 miles the big Colorado flows through the Grand Canyon. Starting 200 million years ago and continuing every day the Colorado River has cut through and reshaped the Grand Canyon sedimentary rock down to the igneous rock. The igneous rock was formed thru plate techtonics more than 200 million years ago So for 200 million years the river cuts through the rock and the rain, snow, and wind erode the canyon's rock walls, which means the sides of the canyon. The Grand Canyon is an excellent example of the force and effect of erosion.