When I stand on the edge of the Grand Canyon, I sense the flow of time. As a photographer, I have spent many hours studying the depths of the canyon, watching the changing light bring color and form to the rocks and buttes. Invariably my thoughts turn to how time is represented by the Grand Canyon.
As I stand on the edge of the Grand Canyon, I sense the flow of time in many dimensions. The most obvious is measured by the watch on my wrist ticking off seconds, minutes, and hours. The sun rises, moves across the sky, illuminating the canyon walls, then sets. Stars become visible; perhaps the moon and the milky way mark night’s passing. Then, the sun returns, and the cycle repeats, never quite the same each time.
A new day begins in the Grand Canyon.
A longer time frame is the passing of the seasons at the Grand Canyon. Warm summer months with monsoon rains begin to cool, and daylight hours shorten in fall. Winter brings cold and snow, highlighting the canyon with white among the red rocks. Spring is marked by warming temperatures, melting snow, and longer days. The seasonal cycle repeats year after year as it has for millennia but never quite the same.
A summer storm gathers in the eastern Grand Canyon.
by human presence
Human presence goes back at least 12,000 years. Archaeologists have uncovered rock shelters, caves, and open campsites with artifacts, tools, and other structures on the rims and in parts of the canyon and several rock art sites, where ancient people created pictographs and petroglyphs on canyon walls. In addition, in the last millennium, ancestral Puebloan groups constructed small villages with multi-room dwellings and kivas, or ceremonial structures. Tusayan Ruin on the south rim is an example of a pueblo occupied between 900 and 1300 A.D.
With the arrival of Europeans in the 1500s, particularly Spanish explorers and later American settlers, the Grand Canyon region witnessed interactions between Native American tribes, traders, trappers, and missionaries. Tribes such as the Havasupai, Hopi, Navajo, and Paiute have historical ties to the Grand Canyon and continue to have cultural connections to the region.
The Watchtower at Desert View is modeled after Ancestral Puebloen buildings and is the location of the Inter-tribal Cultural Heritage Site.
The widening of the Grand Canyon has happened over five to six million years, caused by erosion. Four processes of erosion are unique to the canyon. The arid climate reduces vegetation that would slow water flow and decrease erosion. Ice wedging is caused by water freezing in cracks prying the rock layers apart. Two seasons of precipitation—summer monsoon rain and winter snow—cause brief, heavy flows down the canyon walls. Finally, the north rim is 1,000 higher, so water flows away from the south rim and toward the river from the north. As a result, the distance from the north rim to the river is much greater than from the south rim to the river
The effects of erosion in widening the Grand Canyon can be seen in this view from Hopi Point,
by uplift and downcutting
A large area of the Earth began to be uplifted 70 million years ago by plate tectonics. This 130,000 square-mile region we call the Colorado Plateau now stands more than 7,000 feet above sea level and is surrounded by lowlands to the west and south. During the uplift, the layers of rock remained horizontal. Gradually a river formed, flowing west and cutting down through the rocks, craving the Grand Canyon into the plateau’s edge and finding its way to the sea.
Looking west from Lipan Point, the dramatic result of downcutting by the Colorado River is clearly visible.
by rock deposition
Water and wind have deposited the various layers of the rock revealed in the canyon walls beginning 525 million years ago. Imagine a sea that covers the land. In deeper waters, the shells of crustaceans fall to the bottom. That is the source of the limestone cliffs such as the Redwall. In shallower water, sand accumulates and is later compressed into sandstone, such as the Tapeats, just above the Inner Gorge. Above the sandy beach, silt and organic matter gather in wetlands to become softer shale layers easily eroded into slopes of mixed rock layers typical of the Hermit Formation. A vast area of sand dunes was compressed into the Coconino Sandstone, just below the rim. These layers of rock were formed over a period of 255 million years.
At the bottom of this stack of rocks lies a rock formation that is 1.8 billion years old. It is composed of granite and metamorphic rocks once buried deep beneath the Earth’s surface called the Vishnu Schist. Over a billion years of geological history have been eroded away between this layer and the overlying sedimentary rocks. Traces of these missing rocks are visible in the eastern area of the canyon along the river.
The layers of sediment laid down in ancient seas and hardened into rock formations are colored by dawn light.
by plate tectonics
What drives all these changes on the face of the Earth? The Earth’s surface is made up of large puzzle-like pieces called tectonic plates. The Grand Canyon is on the North American plate. It is moving slowly, driven by currents of molten rock deep within the Earth. The plates have shifted and changed position over billions of years, causing the land to rise and fall, forming mountains, valleys, plateaus, and ultimately the Grand Canyon. It is a continuous process causing the Earth to slowly evolve over time.
A beam of sunlight marks the passage of another day at the Grand Canyon.