One of the iconic images of Lake Superior's North Shore is no more. MPR’s Bob Kelleher reports that a rock bridge known as a sea arch on the shoreline in Tettegouche State Park has collapsed, leaving behind a tree-covered stone pillar isolated in the lake.

Sea arches form from caves hollowed out by waves from two different directions opening the cave into an arch. Eventually, the combination of waves, freeze and thaw cycles and erosion bring an arch down. The Tettegouche arch was the only arch along Minnesota's share of the North Shore. It formed in hard basalt rock hundreds, or possibly thousands, of years ago.