It is formed by the structure known as the Purbeck Monocline. It is the largest exposed monocline in North America. The flat-lying Chuska Sandstone rests unconformably on Mesozoic rocks deformed in the Defiance monocline. The summit is in elevation and is part of the Waterpocket Fold, a nearly monocline. Landslides and narrow gullies have formed along the northern edge of the monocline. The whole crust in the area was bent into a monocline. The strata are part of a gentle (2-6 degrees) westward dipping monocline. Furthermore, Paleozoic field locations roughly align with the northeast-trending Hogback monocline. The Purbeck Monocline defines the field's southern limit. The Purbeck Monocline is a geological fold in southern England. At a time in the past, monocline formed to the west of Sydney. The southwestern and southern flank of the uplift is marked by the Terlingua Monocline. The monocline continues under the English Channel as the Wight-Bray Monocline. During subduction the western end of the forearc region flexured downward forming a giant monocline. The west section of the Butte Fault is the East Kaibab Monocline.