Mile 62 - The Grand Canyon Proper
Major Powell noted a distinction between Marble Canyon and Grand Canyon following his expeditions of 1869 and 1871-72. Also, river runners often notice that below the Little Colorado River, the main canyon quickly becomes much deeper and foreboding as the river leaves Marble Canyon and begins to bend west into Grand Canyon proper. As the Colorado bends and cuts deeper into the Kaibab Plateau, the gradient becomes steeper as the river flows over extremely hard strata, such as granite and schist. In addition to this, it is also important to note that Marble Canyon and Grand Canyon share many similarities such as much of their geologic composition. One way to look at this change is that Grand Canyon proper is basically an expansion of Marble Canyon, or another way to look at it is that Marble Canyon simply composes the upper reaches of greater Grand Canyon.