Short answers, pulled from the story.
The Colorado River has been carving the Grand Canyon for five million years. This geological process has created a wound in the earth so deep that the air at the bottom is significantly warmer and drier than the plateau above.
The Yarlung Tsangpo Grand Canyon in Tibet, China is regarded by some as the deepest canyon on Earth, plunging 5,500 meters below the surrounding peaks. This massive chasm is slightly longer than the Grand Canyon in the United States.
Evidence of archaic humans has been discovered in Africa's Olduvai Gorge, a site that has yielded some of the most important fossils of early hominids. This location includes the famous Zinjanthropus fossil.
The Valles Marineris on Mars is the largest known canyon in the Solar System, stretching over 4,000 kilometers long and reaching depths of up to 7 kilometers. This massive chasm is located on the equator of Mars and could fit the entire United States within its boundaries.
The word canyon is Spanish in origin, derived from the Spanish cañon meaning tube or pipe. This term was adopted into English to describe deep clefts between escarpments or cliffs, distinguishing them from the wider, more open ravines found in Europe.