The rock formations of the Escalante area have been designated the Escalante Member of
Entrada Sandstone of the
San Rafael Group by geologists, and were formed in the
Middle Jurassic epoch (166 to 174 million years ago). The
Straight Cliffs Formation of the
Kaiparowits Plateau to the west of the Devils Garden were formed during the more recent
Cretaceous period.
Paleontologists are interested in the area because the rock formations were deposited when the dinosaurs roamed the Earth. Many dinosaur fossils and tracks have been discovered by scientists working within the boundaries of the GSENM. The natural arches and other formations were created, and continue to be shaped, by the natural processes of
weathering and
erosion. Some of the rock layers are composed of a harder
caprock material which resists the effects of weathering and erosion. Those caprock layers will remain intact much longer than other less resistant layers which weather and erode away below and around them leaving behind the current arches and hoodoos. Cycles of heat and cold, precipitation, ice, wind and gravity all play a part in the creation of the formations. Daily extreme temperature variations create
fractures by repeated expansion and contraction of the rock in a process called
thermal stress weathering. The thermal stresses can cause deep cracks that split the rock into separate pieces in an erosional process called thermal
exfoliation. Precipitation causes
dissolution of the fine crystalline grains that bind the larger particles together, which is known as
chemical weathering. Freezing water expands in fractures making them wider and deeper in a process called
frost weathering. Gravity exerts a constant downward force that creates new fractures and separates the formations along existing fractures in a process called
stress relief exfoliation. High speed winds remove any loose grains from the formations and wind-borne particulates
sandblast the surfaces making them smoother. == Wilderness ==