ABSTRACTS
How Blind Are We? Reading a Picture
Figure 1 shows an outcrop at Grand Canyon, about a half mile along the trail to Clear Creek from Phantom Ranch and Bright Angel Creek. The Vishnu Schist occupies the bottom two-thirds of the photo, and the Tapeats Sandstone the upper third, separated by the Great Unconformity (Figure 2). There is a bleached zone and an obvious cavity near the center of the picture. While outliers of Precambrian sediment occur less than a mile away, at this location they are completely eroded
How Blind Are We? Reading a Picture