Arizona and the Grand Canyon

The Grand Canyon

Sunday we spent the entire day at the Grand Canyon. Of course, one day is not nearly enough time to experience the Canyon, but it is better than postcards and words, which cannot convey the incredible experience of standing on the Canyon rim and peering into millions of years of geologic history. Unfortunately, our pictures are also inadequate to do the Canyon justice.

December is a perfect time to go! It was chilly, and we had to bundle up against the wind, but few other tourists accompanied us, leaving us to absorb the beauty at our own pace in peace and quiet. And we were able to drive to places that during other times of the year tourists have to board buses to see. We can't imagine having to push one's way through wall-to-wall crowds just to glimpse the scenery—and in 90° heat!

Our first stop along the South Rim was Mather Point [left], which is the observation point closest to the Visitor Information Center. From there we drove west, along Hermit Road, stopping at each lookout (Yavapai, Maricopa [below], Powell, Hopi, Pima) for the changing viewpoint. Our west-bound drive ended at the Hermit's Rest, where we entered the small lodge to find a giant fireplace roaring with welcome heat, and generously offered hot apple cider.

We then doubled back and followed Desert View Drive east, again stopping at lookouts along the way (Yaki, Grandview, Moran, Lipan). Time was running out so we didn't stop at the Tusayan ruins and museum, and we ended our visit at the Desert View Watchtower.

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Geology

Newest research suggests that the Colorado River has carved the Grand Canyon in quick, violent spurts from massive flooding beginning probably a mere 5-1/2 million years ago. Because its headwaters in Colorado are almost 2 miles above sea level, the river picks up tremendous velocity as it plunges toward the Gulf of California. This creates remarkable carrying power: the Colorado River can transport hundreds of thousands of tons of sand and silt, scooped from its channels and tributaries upstream, in a single day.* The section of the river that runs through the Canyon is 277 miles long; a nonmotorized board takes 14 to 16 days to "run" the full canyon.

While the river deepens the canyon, other erosional forces widen it. Erosion nibbles Grand Canyon into towering cliffs alternating with gentle slopes. This cliffs-and-slopes profile is typical of erosion in a relatively dry climate. During the long winter, moisture seeps into the cracks in the rocks, prying them apart as it freezes overnight. In spring and summer, streams of snow-melt and rain carry loosened gravel and boulders down the Canyon's steep walls to the river, gouging out tributary canyons and isolating ridges [above]. The tributary canyons funnel debris into the river in heaps. Turbulent rapids occur where the river meets these obstacles, creating white, frothing waves that can be heard from the Canyon rim [Pima viewpoint, below] .

Rain becomes acidic as it combines with carbon dioxide in the air. It can dissolve limestone, including the cement holding grains of sandstone together. As this water percolates through the soil, acids secreted by lichens and plant roots make it even more acidic. Trickling along cracks in the rock, the water hollows out hidden caverns deep within the walls of the Canyon.

Gravity plays a part in erosion, too, triggering landslides of poorly cemented formations and prompting unsupported rocks to fall. As the soft Hermit Shale crumbles into a gentle incline, it undermines the hard, Coconino Sandstone. Slabs of unsupported Coconino detach from the Canyon walls, forming sheer cliffs. Most of the slabs slide gradually downslope, but some break free to fall, shattering with the impact of their own weight.

Besides erosion, the other two important geologic processes are deposition—when water and wind deposit mud, sand, and dirt—and plate tectonics. These processes work on the landscape in a continuous cycle.

At Grand Canyon, there have been three, distinct erosional cycles.

The earliest cycle began 2 billion years ago, when sediments began building on the floor of a sea. Deposition of these sediments continued for 300 million years. Heat and pressure mixed and recrystallized the original sediments into dark masses of rocks called schists. Tectonic activity formed the schists into great mountains. Erosion attacked these mountains for another 300 million years, eventually wearing them down to a level plain.

Little evidence is left of the second cycle. One scrap of this lightly-tilted group of rock layers may be seen from Desert View or Cape Royal; another is visible from viewpoints around Grand Canyon Village. The rocks began to accumulate as a sea encroaching across the eroded base of the early mountains. Calcium carbonate then sifted down in a limey ooze, entombing the first signs of life to be fossilized at the Canyon. After almost 600 million years of deposition, the rock—limestones, shales and sandstones—was 2 miles thick. Then another range of mountains was born through tectonic activity. Erosion subsequently stripped away all but a few islands of these new mountains. This period of erosion lasted a quarter of a billion years.

[At right are the Canyon and Colorado River from Lipan Point.]

The third cycle created the upper, horizontal layers of Grand Canyon, including the rocks now exposed on the rim. It began more than 500 million years ago, as seas advanced, retreated, and advanced again more than a dozen times. Layer after layer of sediments formed on ocean floors, shorelines, and in swamps. The layers that were deposited over the Kaibab Limestone that now forms the Canyon rim have already eroded away. During their formation, dinosaurs evolved, flourished, and became extinct. About 65 million years ago, the entire region began to rise tectonically. Erosion began attacking the bulge, and is still at work today. In fact, scientists now think that some parts of the Canyon may be only 750,000 years old, and in some places, it may still be growing.

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History

There is archeological evidence of humans living in the Canyon as long ago as the 10th century. Europeans first arrived in 1540 with Coronado's conquistadors. By the 1820s, French and Anglo-American beaver trappers were working western rivers. Mexico ceded the Southwest, including the Grand Canyon, to the United States in 1848.

The first expedition up the Colorado River took place in 1858, ordered by the War Department to determine whether the river could be used to support military expeditions against the independent government of Utah.

In 1871 there was a brief gold rush to the Canyon, but the gold was too fine to be recovered. However, prospectors continued to probe for decades for other minerals, including silver, copper, and later uranium. In 1882, the Atlantic and Pacific Railroad completed a line that opened up Grand Canyon to the outside world. A crude tourist hotel was built at Diamond Creek in 1884 but closed after five years. In 1901, the Santa Fe completed a railroad line on the plateau from Williams to Grand Canyon Village.

President Theodore Roosevelt proclaimed Grand Canyon a Game Preserve in 1906, then used the national Antiquities Act to the justify National Monument status in 1908. In 1919, President Woodrow Wilson signed legislation that redesignated the monument as Grand Canyon National Park. Mining and stock raising were phased out, and tourist facilities were to be limited to preserve the Canyon's beauty. The Grand Canyon National Park Enlargement Act of 1975 extended protection to the western Canyon and the lower Granite Gorge, as well as Marble Canyon.

The Watchtower [right] was designed by Mary Colter, who also designed the Canyon's Hermit's Rest (1914), Lookout Studio (1914), and Bright Angel Lodge (1935). She chose regional themes for all of her buildings at the Canyon and intended her designs to blend with both the landscape and culturally. To maintain authenticity, she employed Hopi and Navajo masons, muralists, and artisans to construct and decorate her buildings, and she chose fixtures and furnishings with Native American elders and artists. The Watchtower (1933) is patterned after the ancient Pueblo towers of Mesa Verde and Hovenweep.

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Cameron, AZ

From the South Rim, we drove south toward Flagstaff but were determined to stop along the way at the town on the map called "Cameron." We arrived there in the dark and searched for the "town" but had trouble finding it. It turned out that Cameron is actually a gigantic souvenir shop, with restaurant! No wonder we drove right past it!

*Source of Grand Canyon geological and historical facts: Grand Canyon, the Vault of Heaven, by Susan Lamb, Grand Canyon Association, 1995.

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