One of Earth's few landforms visible from space, the Grand Canyon of the Colorado River
slices through 277 miles of Northwestern Arizona. While there are certainly deeper canyons,
no where else on Earth has width, depth and length combined in such a way as to produce
anything quite like this breathtaking chasm. Over the course of 6 million years, the canyon
has been carved by the Colorado River. A mile deep, 277 miles long, and up to 18 miles wide,
this canyon is like none other.
Grand Canyon begins at Lees Ferry, which is where river runners today start their rafting
adventure down the Colorado River. Here, the first of Grand Canyon's many rock layers
is exposed. At 270 million years in age, the whitish-gray Kaibab Limestone is the youngest
in a series of layered sedimentary rocks, each emerging as the river carves its way
deeper into the Colorado Plateau.
Entering on the left we see the Little Colorado River. At this point the main Colorado River
turns west, carving through the Kaibab Uplift, exposing both the reddish pink Supergroup
rocks and the dark rocks of the inner gorge.
The river divides the uplift into two plateaus, which form the North Rim and South Rim of
the canyon. Flying over the South Rim and Grand Canyon Village, we enjoy a view of the
canyon well-documented by almost four and a half million visitors each year. From the
village, visitors gain access to the Bright Angel Trail, a popular pathway for canyon
hikers, established here because the Bright Angel Fault has fractured the otherwise impenetrable
cliffs.
Following the Bright Angel Fault across the canyon to the north, we arrive at the North
Rim, which reaches elevations over 9,000 ft. As we pass, note the Kaibab Monocline, which
forms the eastern edge of the Kaibab Uplift.
We return to the river down Crystal Creek. In 1966 a large storm caused a debris flow
to surge down Crystal Creek, enter the Colorado River and create overnight one of the toughest
rapids on the river.
Ahead is Powell Plateau, an erosional remnant of the North Rim named for John Wesley Powell,
who, in 1869, was the first explorer to survey and map the canyon from one end to the other.
At Powell Plateau the character of the canyon changes. Here the Esplanade Sandstone, one
of the Paleozoic rock layers, forms a wide, red rock bench within the canyon. Fossils
in the Paleozoic rocks provide evidence of the region's dynamic geologic history. Shellfish,
coral, reptile tracks and fern fossils reveal the ancient oceans, deserts and swamps that
once existed here.
On the left, is Havasu Creek. This creek is famous for its blue-green water, stunning
waterfalls and travertine pools. This is the traditional home of the Havasupai, or "people
of the blue-green waters," who still occupy the canyon today.
Further downriver, we approach Vulcan's Throne, the remnant of an ancient volcano.
Beginning 630,000 years ago, lava poured forth over the canyon rim from volcanoes such as
this, damming the river at least 13 times. Each time the river was blocked, water collected
behind the dams. Eventually the weight and pressure of the water caused them to catastrophically
fail. Remains of these dams can still be seen perched on the cliff walls. Volcanic eruptions
came to an end about 10,000 years ago.
Upon passing the lava flows, we cross the Hurricane Fault, one of a series of north
to south trending faults that cut across the canyon. The Hurricane Fault was originally
active during the Precambrian Era, but has been reactivated numerous times since. Like
fossils, faults provide insight into Grand Canyon's complex geologic history.
Many fault-oriented tributaries are visible in this section of the canyon, including Separation
Canyon, named such because it was here that three of John Wesley Powell's men left the
group in 1869, never to be seen again.
Long before Powell visited the canyon, prehistoric peoples were living along the river. Rock
art, cliff dwellings and pot sherds serve as evidence of their presence here. Additionally,
caves throughout the canyon contain the remains of large ice age mammals, such as giant ground
sloth, camels, mastodon, and horses. The discovery of clovis style spear points indicates that
ice age hunters also dwelled within the canyons walls 12,000 years ago.
Our 277 mile journey through Grand Canyon ends abruptly at the Grandwash Cliffs. As
we pull away, the full, spectacular length of this grandest of all canyons comes into
view once again. The geologic story of this impressive feature is complicated, but with
each day we learn something new. As time passes, the aged rocks will continue to be eroded.
Although we can only imagine how this feature will appear in the next million years, its
value as a geologic and visual masterpiece is apparent and we will continue to protect
it for generations to come.