116. Iona's Beach

Iona's Beach SNA

Famous pink shingle beach composed of smooth rhyolite pebbles that produce a chiming sound under wave action.

Iona's Beach Scientific and Natural Area Click to open side panel for more information , located along Lake Superior near Two Harbors, Minnesota, is renowned for its rare salmon-pink shingle beach and acoustic "singing" rocks. Its geology is rooted in Proterozoic volcanic activity from the Midcontinent Rift System roughly 1.1 billion years ago, shaped continuously by coastal weathering and wave dynamics.

Key Geological Features

• Dual Igneous Bedrock Framing: The crescent-shaped shoreline is bookended by two distinct igneous rock formations. To the north sits a roughly 30-foot cliff of silica-rich felsite and pink rhyolite bedrock, while the southern end is bounded by a headland of dark grey basalt.

• Rhyolite Shingle Formation: Storm waves and freeze-thaw frost wedging break off fragments of pink rhyolite from the northern cliff. As wave action carries these shards downshore, the water grinds and polishes them into flattened, smooth, palm-sized stones called "shingles."

• Basalt Trapping Mechanism: The dark basalt headland at the southern end acts as a natural groin, preventing the drifting rhyolite pebbles from washing further down the coastline and confining them to a 300-yard arc.

• Acoustic Wave Effect: Because the rhyolite stones are flat and uniform, receding waves lift and tumble them over one another, producing a characteristic tinkling or ringing sound often referred to as the beach "singing."