Diamond Peak, Oregon

Diamond Peak (8,750 feet, 2,667 meters), the dominant landform in the Willamette Pass area, is a basaltic andesite shield approximately 3.6 cubic miles (15 cubic kilometers) in volume. Like other shields in the area, it has a central pyroclastic cone that is surrounded and surmounted by lava flows. Diamond Peak began erupting from a vent near its northern summit. A second vent later opened near the southern summit, piggy-backing its lava and tephra over the previously erupted volcanic rocks. This vent migration likely involved only a small interval of time. Diamond Peak is probably less than 100,000 years old, but is certainly older than the last glaciation, which ended approximately 11,000 years ago.