Mount Baker

Snow and ice-covered Mount Baker, in Whatcom County, is the highest peak in the North Cascades — 3,286 m or 10,781 ft — and the northernmost volcano in the conterminous United States. USGS places it at 48.777° N, 121.813° W. It is an andesite stratovolcano. The National Volcano Early Warning System rates its threat potential as Very High.

It is the only U.S. volcano in the Cascade Range affected by both alpine and continental glaciation. The cone is composed mainly of andesite lava flows and breccias and was largely formed before Fraser Glaciation, about 25,000 to 10,000 years ago. The most recent major eruption, about 6,700 years ago, began with flank collapses that sent lahars down the Middle Fork and Nooksack Rivers and down the east flank, damming Baker River and creating Baker Lake, and ended with a widespread tephra fall.

In 1975–76, magma intruded Sherman Crater, immediately south of the summit, without erupting. Steam emission there has been higher since 1975. USGS calls Mount Baker the youngest volcano of a larger field that has been recurrently active for the past 1.3 million years, about 50 km (31 mi) east of Bellingham Bay and 25 km (16 mi) south of the Canadian border.