Find Sitka's Bedrock

The place you travel through today is very different from the place you might have traveled through millions of years ago. The bedrock under you is a sedimentary rock called Sitka Graywacke. It formed on the floor of the Pacific Ocean back when dinosaurs ruled the earth. Graywacke is... gray in color. It is made of small, squished-together pieces of mud and sand eroded from other rocks. After forming at the bottom of the ocean, this graywacke was gradually pushed upward into its present position by motion between the Pacific tectonic plate and the North American tectonic plate. This bedrock was shaped by other forces more recently: glaciers during the last ice age and, more recently, the Pacific Ocean and Kaasda Héen (Indian River). Over ten thousand years ago glaciers carved Sitka Graywacke near Merrill Rock into the smooth, curvy shapes you find now. Ocean tides and waves broke the bedrock down further into cobble- and sand-covered beaches. Water in Kaasda Héen also moved broken bedrock down to this beach, smoothing it into cobbles along the way.