The Hoh River flows from the western side of Olympic National Park. Much of its water comes from melting glaciers on the peaks of the Olympic Mountains. This glacial water contains fine powdered rock formed by the grinding action of the glacial ice against rocks. When the glacier melts the rocks in the glacier wash downstream piling up in gravel bars in the river channel. The fine powdered rock gives the water its milky appearance. All glacial streams have this milky appearance.