But these east-and-west cliffs and the plateaus which they form are divided by north-and-south lines in another manner. The country has been faulted along north-and-south lines or planes. These faults are breaks in the strata varying from 1,000 or 2,000 to 4,000 or 5,000 feet in verticality. On the very eastern margin the rocks are dropped down several thousand feet, or, which means the same thing, the rocks are upheaved on the west side; that is, the beds that were originally horizontal have been differentially displaced, so that on the west side of the fracture the strata are several thousand feet higher than they are on the east side of the fracture. The line of displacement is known as the Echo Cliff Fault. West of this about twenty-five miles, there is another fault with its throw to the east, the upheaved rocks being on the west. This fault varies from 1,500 to 2,500 feet in throw, and extends far to the northward. It is known as the East Kaibab Fault. Still going westward, another fault is found, known as the West Kaibab Fault. Here the throw is on the west side,--that is, the rocks are dropped down to the westward from 1,000 to 2,000 feet. This fault gradually becomes less to the northward and is flexed toward the east until it joins with the East Kaibab Fault. The block between the two faults is the Kaibab Plateau. Going westward from 60 to 70 miles, still another fault is found, known as the Hurricane Ledge Fault. The throw is again on the west side of the fracture and the rocks fall down some thousands of feet. This fault extends far northward into central Utah. To the west 25 or 30 miles is found a fault with the throw still on the west. It has a drop of several thousand feet and extends across the Rio Colorado far to 94 CANYONS OF THE COLORADO. the southwest, probably beyond the Arizona-New Mexico line. It also extends far to the north, until it is buried and lost under the Pine Valley Mountains, which are of volcanic origin.