Bright Angel Trail
From the Trail View Point (2093m altitude) I took this view looking down at the Bright Angel Trail, twisting and zigzagging as it disappears down from the South Rim of the Grand Canyon. The trail descends all the way down to the Colorado River in the inner canyon (not visible above), across the river and then up onto the North Rim (seen in the far distance). The trail seen in the mid-left of shot is a different path from Havasupai Gardens which goes to Plateau Point (1050m) at the edge of the Tonto Platform.
The rocks forming the Tonto Platform were laid down between 525 and 500 million years ago in the Palaeozoic era. The Redwall cliffs, which range from 120-240m high in the Canyon form much of the path of the Bright Angel Trail's upper reaches. They began being laid down some 65 million years after the Tonto Platform's rocks. This gap in time is called and unconformity; geologists are still puzzling out exactly what happened in this interval.
The weathering of the Grand Canyon exposes nearly 40 major sedimentary rock layers which range in age from about 200 million to nearly two billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores in western North America. Both marine and terrestrial sediments are represented, including fossilised sand dunes from an extinct desert. There are at least 14 known unconformities in the geologic record found in the Grand Canyon area.
Uplift of the region started about 75 million years ago during the Laramide orogeny, a mountain-building event that is largely responsible for creating the Rocky Mountains to the east. In total, the Colorado Plateau was uplifted an estimated 3,200m.
Wetter climates brought upon by ice ages starting two million years ago greatly increased excavation of the Grand Canyon, which had nearly reached its currently depth 1.2 million years ago. Volcanic activity deposited lava over the area 1.8 million to 500,000 years ago. At least 13 lava dams blocked the Colorado River, some forming lakes which were more than 600m deep.
The end of the last Ice Age and subsequent human activity has greatly reduced the ability of the Colorado River to excavate the canyon. Dams in particular have upset patterns of sediment transport and deposition. Controlled floods from Glen Canyon Dam upstream have been conducted to see if they have a restorative effect. Earthquakes and mass wasting erosive events still affect the region.
Earlier shots in my Arizona album show the upper reaches of the Bright Angel Trail (in snow). Scanned from a negative.
Bright Angel Trail
From the Trail View Point (2093m altitude) I took this view looking down at the Bright Angel Trail, twisting and zigzagging as it disappears down from the South Rim of the Grand Canyon. The trail descends all the way down to the Colorado River in the inner canyon (not visible above), across the river and then up onto the North Rim (seen in the far distance). The trail seen in the mid-left of shot is a different path from Havasupai Gardens which goes to Plateau Point (1050m) at the edge of the Tonto Platform.
The rocks forming the Tonto Platform were laid down between 525 and 500 million years ago in the Palaeozoic era. The Redwall cliffs, which range from 120-240m high in the Canyon form much of the path of the Bright Angel Trail's upper reaches. They began being laid down some 65 million years after the Tonto Platform's rocks. This gap in time is called and unconformity; geologists are still puzzling out exactly what happened in this interval.
The weathering of the Grand Canyon exposes nearly 40 major sedimentary rock layers which range in age from about 200 million to nearly two billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores in western North America. Both marine and terrestrial sediments are represented, including fossilised sand dunes from an extinct desert. There are at least 14 known unconformities in the geologic record found in the Grand Canyon area.
Uplift of the region started about 75 million years ago during the Laramide orogeny, a mountain-building event that is largely responsible for creating the Rocky Mountains to the east. In total, the Colorado Plateau was uplifted an estimated 3,200m.
Wetter climates brought upon by ice ages starting two million years ago greatly increased excavation of the Grand Canyon, which had nearly reached its currently depth 1.2 million years ago. Volcanic activity deposited lava over the area 1.8 million to 500,000 years ago. At least 13 lava dams blocked the Colorado River, some forming lakes which were more than 600m deep.
The end of the last Ice Age and subsequent human activity has greatly reduced the ability of the Colorado River to excavate the canyon. Dams in particular have upset patterns of sediment transport and deposition. Controlled floods from Glen Canyon Dam upstream have been conducted to see if they have a restorative effect. Earthquakes and mass wasting erosive events still affect the region.
Earlier shots in my Arizona album show the upper reaches of the Bright Angel Trail (in snow). Scanned from a negative.