The formation of the Grand Canyon, caused by tectonics and erosion
National parks
978-3-14-100890-6 | Page 189 | Ill. 4
Overview
The Grand Canyon is a unique natural wonder and the best possible "textbook" on the geological history of the Earth. It was formed by the immense, erosive power of the Colorado River, which over millions of years, has carved its 2335 km way from the Rocky Mountains to the Gulf of California, deep into the Colorado Plateau.
Formation by tectonic erosion
About 50 million years ago, the collision of two tectonic plates caused the land to be elevated several thousand metres. The rock layers of the Colorado Plateau, which are sedimentary rock deposits covering a much older basement rock, remained almost unscathed and in a horizontal position.
Because the rock layers have varying degrees of hardness, resistance to the erosive power of the water also varies. The soft layers of rock erode quicker than the hard layers. One result is the distinct step-like profile that is a feature of the Grand Canyon walls today. Extreme temperature changes, from hot to cold, root pressure or strong wind can also loosen and disintegrate rock on the valley sides. However, due to the dry climate these weathering processes transpire relatively slowly.
Formation by tectonic erosion
About 50 million years ago, the collision of two tectonic plates caused the land to be elevated several thousand metres. The rock layers of the Colorado Plateau, which are sedimentary rock deposits covering a much older basement rock, remained almost unscathed and in a horizontal position.
Because the rock layers have varying degrees of hardness, resistance to the erosive power of the water also varies. The soft layers of rock erode quicker than the hard layers. One result is the distinct step-like profile that is a feature of the Grand Canyon walls today. Extreme temperature changes, from hot to cold, root pressure or strong wind can also loosen and disintegrate rock on the valley sides. However, due to the dry climate these weathering processes transpire relatively slowly.
