Thayer Glacier lies on the east slopes of North Sister in Oregon’s Cascade Range at more than 8,000 feet, on the flank of an extinct shield volcano in one of central Oregon’s highest volcanic landscapes. In August 2020, the Oregon Glaciers Institute reported that it no longer had active, moving ice. It remains a named glacier, but with little or no true glacial movement, illustrating the wider retreat of small mountain glaciers in the Cascades.