The Grand Canyon is 446 km long, up to 29 km wide, and 1.6 km deep. The walls of the Grand Canyon are composed of nearly 40 different rock layers that represent about 1 billion years of Earth’s history. The rocks at the bottom of the canyon are metamorphic rocks formed 1.75 billion years ago. New sediments were deposited on top of those rocks, and mountain-building events around 755 million years ago tilted and lifted the new rocks. The total sandstone, shale, and limestone layers were deposited between 1,000 and 250 million years ago to form a rock sequence up to 1,525 m thick. WRITE YOUR ANSWER ON THE LINEIDENTIFY two geologic processes occurring in the Grand Canyon today that also contributed to the formation of the rocks that make up the Grand Canyon’s walls.