On the north side of Mount Brandon, glaciers -- now long gone -- have cut a great deep gash in the mountain's flank.
Along the old pilgrim path up through the valley are revealed splendid examples of cross-bedding in the 400 million year-old sandstone.
Here fine red sand was swept by wind into dunelike layers, truncating other layers at odd angles, giving us a glimpse across the eons of a dry inland basin on a long-vanished continent where sediments collected from surrounding uplands.
Geologists, too, have walked this pilgrim's path, teasing out the story of the Earth's transformations. They understand what the Irish saint Columbanus taught 1400 years ago: The creation is the primary revelation.