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Ride The Rockies

2012 Ride The Rockies with USGS

Day-by-Day Geology Highlights

Ride The Rockies 2012 logo>

DAY 1 – SUNDAY, JUNE 10 – Gunnison to Hotchkiss – 79 miles

Black Canyon of the Gunnison, Colorado

Gunnison has the distinction of being one of the coldest places in the conterminous U.S. during the winter. In a valley today, Gunnison was once near the crest of an old highland of the Ancestral Rockies (245–320 million years ago).

Along our route, we’ll see Dillon Pinnacles north of Blue Mesa Reservoir. Violent volcanic eruptions and mudflows from stratovolcanoes of the West Elk Mountains about 30 million years ago formed the rocks that comprise the Pinnacles. The larger rock fragments act like a cap to protect the underlying softer, muddy ash material from erosion, resulting in the spires.

Black Canyon of the Gunnison, Colorado_resized for web

We pedal through the north part of Black Canyon of the Gunnison National Park, where the Gunnison River cut a deep gorge (2,425 ft, 740 m) through Precambrian-age gneiss and schist (about 1,800 million years old). Taken together, the depth and narrowness are what give the Black Canyon its name—a reference to the lack of sunlight rather than the color of the rocks, which are a combination of gray, white, black, and pink.

DAY 2 – MONDAY, JUNE 11 – Hotchkiss to Carbondale – 68 miles

Today, we ride along the physiographic province boundary between the plateaus (west) and the mountains (east). We’ll pass evidence of coal mining in Paonia before we ascend McClure Pass.

Crystal, CO - (c) Glenn A. Smith Photo

The Yule Marble Quarry in the town of Marble furnished marble that was used in the Lincoln Memorial and the Tomb of the Unknown Soldier.

Mt. Sopris (c) Rian Houston

Our northerly route gives us a spectacular view of Mt. Sopris as we descend into the Crystal River Valley. Rising 6,250 ft (1,905 m) above the valley floor, such relief makes Mt. Sopris seem higher than its 12,953 ft. Mt. Sopris is made up of granitic rock solidified from magma that intruded about 34 million years ago—coincident with much igneous activity elsewhere in Colorado.

Dark red rocks comprising clays, sands, and gravels of the Maroon Formation (Middle-Late Pennsylvanian through Early Permian; 260 to 310 million years old) make up the hillsides along the Crystal River and Roaring Fork River Valleys.

DAY 3 – TUESDAY, JUNE 12 – Carbondale to Leadville – 83 miles

Maroon Bells (c) Norm Herr

Folded and faulted Paleozoic (251 to 542 million years old) rocks host the mineral-rich deposits of gold, silver, lead, and zinc that were mined in Aspen from 1879 to 1893. Situated on a wide, nearly flat expanse of glacial outwash, the lower limit of glaciation extended 2 to 3 miles below Aspen. Thousands of feet of ice carved the U-shaped valley of the Roaring Fork River Valley during the Ice Ages of the Pleistocene (maximum extent at about 18,000 years ago).

Indepenence Pass - (c) Rian Houston

The highest point on our tour, at 12,095 ft, Independence Pass bisects the Continental Divide through the Sawatch Range. Directly east of the pass is Mt. Elbert.

Twin Lakes - (c) Rian Houston

Tunnels under the Continental Divide transport Western Slope water to Twin Lakes, where it is stored for downstream power generation and eventually, Eastern Slope water. Moraines of Pleistocene glaciers (maximum extent at about 18,000 years ago) form the dams of Twin Lakes.

We’ll turn and ride northward on Highway 24 up the Arkansas River Valley between the Sawatch west) and Mosquito (east) Ranges. The Arkansas Valley is the northern extension of the Rio Grande Rift, which began forming 30 to 26 million years ago. The rift is formed by a series of half grabens (elongate blocks of rock down-dropped along one side; the faults of the Rio Grande Rift flip-flop from the west to the east sides of the rift valley). The headwaters of the Arkansas River lie below Mt. Elbert, Colorado’s tallest peak (at 14,433 ft).

The Leadville Mining District and other nearby districts together produced about 1.9 million tons of zinc, 1.3 million tons of lead, 333 million ounces of silver, and 3.6 million ounces of gold ore from 1860 through 1998.

DAY 4 – WEDNESDAY, JUNE 13 – Leadville to Granby – 94 miles (with 108-mile option)

We pass the remnants of the Climax Mine as we pedal over Fremont Pass. Twenty-two million years ago, three successive intrusions formed the ore bodies from which molybdenum was mined. Molybdenum confers toughness to our steel bicycle frames.

Lake Dillon - (c) Rian Houston

Leaving Frisco, we skirt the shores of Lake Dillon, the largest water-storage facility for the Denver metropolitan area. A tunnel moves water from Lake Dillon under the Continental Divide to Denver.

Eside Hwy9_Williams Fork Mtns_resized for web

Heading north, down the Blue River valley from Frisco, jagged glaciated peaks of the Gore Range border the west and the rounded topography of the Williams Fork Mountains frames the east. The Williams Range thrust fault defines the western edge of the Front Range where Precambrian-age gneiss and granite (1.4 to 1.8 billion years old) override Upper Cretaceous Pierre shale (70 to 82 million years old). More durable Mesozoic rocks are exposed as we ascend from the easily erodible shale of the valley.

An active molybdenum operation in the Williams Fork River Valley, ore is transported along a 15-mile conveyor belt through an old train tunnel from the Henderson Mine, east of the Continental Divide, to the Henderson Mill on the west side. The Henderson Mine is the largest primary producer of molybdenum in the world.

At Parshall, our route joins the Colorado River as we pedal east up the valley into a canyon cut through a variety of rock types sliced by faults. The canyon opens into MiddlePark, the middle of three relatively featureless surfaces in the high mountains of Colorado.

DAY 5 – THURSDAY, JUNE 14–Granby to Estes Park – 63 miles

Colorado River Valley (above Granby, Colorado)_resized for web.jpg

Today’s ride crosses the Continental Divide along Trail Ridge Road, the highest, continuous paved highway in the country. Glaciers carved broad flat valleys, and left behind cirques (semicircular-shaped bowls sculpted by glaciers at the heads of mountain valleys) and moraines (ridges made up of mixtures of rock material of various sizes and shapes) along the valley walls and downvalley where the glaciers ended. As we ascend the valley of the Colorado River, we follow the path of the longest Ice Age glacier (20 miles) of Rocky Mountain National Park. Above timberline on our descent, the view to the south is dominated by the major glacial valley of Forest Canyon in which ice was 1,000-1,500 ft thick and flowed eastward more than 13 miles.

Cyclists on Trail Ridge Road, Colorado_resized for web

DAY 6 – FRIDAY, JUNE 15 – Estes Park to Fort Collins – 55 miles

Our route takes us down Big Thompson Canyon where, on July 31, 1976, a devastating flash flood swept down the steep and narrow canyon claiming the lives of 144 people and causing over $35 million (1977 dollars) in damages. Unusual atmospheric conditions lead to a large stationary thunderstorm releasing 7.5 inches of rainfall in about an hour.

Big Thompson Flood—30 Years Later (6.4 MB PDF)

Big Thompson Flood, looking upstream into the Narrows

Mouth of (Big) Thomson Canyon west of Loveland

Horsetooth Reservoir - (c) Lou Maher

The Dakota Hogback forms a prominent ridge along the eastern edge of Horsetooth Reservoir as we near Fort Collins.


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