Multipitch Madness: Geology and Climbing in Redfish Canyon of the Sawtooth Range, central Idaho

Summary

Geology professor Shawn Willsey climbs the seven-pitch Super Slabs route in Redfish Canyon, in Idaho’s Sawtooth Range, using the exposed rock and surrounding landscape to explain the area’s geology and glacial history.

Sawtooth Granite

The climbing buttress is part of the Sawtooth pluton. Its pinkish granitic rocks formed when magma cooled and solidified deep underground. The granite dates to the Eocene, approximately 45–50 million years ago.

Evidence of Glaciation

Much of the rock surface is smoothly polished and marked with striations. These features formed as glaciers moved through the canyon, scraping the bedrock with grit and rocks embedded in the ice. The striations indicate the direction of ice movement. The polished rock is also very slippery for climbers.

Inferring Glacier Extent

Glacial polish and striations can help estimate how high the ice reached. If the marks disappear higher on a slope, that may indicate the glacier’s upper limit. If they continue to the top, they show that the glacier reached at least that high.

Marks visible across the climb suggest that ice in Redfish Canyon reached roughly 1,000 feet above the valley floor, at minimum.

Glacial Landforms

The canyon has a broad, U-shaped profile. Smaller tributary glaciers carved hanging valleys that enter the main valley. Willsey describes the Redfish Canyon glacier as the longest and largest in the Sawtooth Range.

Miarolitic Cavities

Some granite contains small cavities thought to have formed from gas pockets in the magma. These cavities can contain quartz crystals; examples shown during the climb include gray quartz.

Researchers or Sources Featured

• Shawn Willsey — Geology professor and presenter. No other researchers or external sources are named.