As you walk along the boardwalk in Cook's Meadow, you'll notice that the ground surface here is relatively flat, as it is just about everywhere in Yosemite Valley. Glaciers gouged out the valley even deeper than it seems, as the actual bedrock floor of the Valley is nearly 2,000 feet, or 600 meters, below where you are standing. As glaciers retreated back this bedrock hole was filled with sediments, leaving a flat valley floor.

Since glaciers retreated from Yosemite Valley about 16,000 years ago, the Merced River has been moving back and forth in a S-shaped pattern across the valley floor. These S-shaped curves are called meander bends. Over time, these bends will get closer together as the river moves and eventually the bends become cut off from the main river channel. The channel-like feature below the boardwalk here is one of these meander bends. Features like this are a reminder that rivers continually change the landscape through time. The wet environment of this abandoned meander is important habitat for plants and animals. Plants adapted to growing in wet conditions thrive in these wetland areas. During certain times of year, large pools of water may occupy these old meanders. These pools and the surrounding areas are critical habitat for aquatic animals, like frogs. Please stay on established trails to protect them.