Sedona Geology
Stage 1: 1,800-65 Million Years Ago
The Yavapai Supergroup is the name for the ancient rocks at the bottom of this diagram. The rocks were formed by plate tectonic processes as volcanic mountains collided with western North America. After a billion years of erosion, the mountains were reduced to a flat layer of schist (gray), granite (pink), and volcanic rocks containing rich copper deposits (black). Above these mountain roots Paleozoic sedimentary layers (blue, red, tan) and Mesozoic layers (green) formed. Most of these layers accumulated on top of a slowly subsiding western margin of North America. |
Stage 2: 80-40 Million Years Ago
During this time, as the Rocky Mountains rose to their heights, central Arizona also rose south of Sedona. This formed mountains known as the Central Arizona Highlands. The uplift resulted in total erosion of overlying Mesozoic rocks (green layers in the diagram above—no longer present in this diagram). The Paleozoic layers, including Sedona’s red rocks, bent and tilted toward the northeast as the highlands rose. Eventually the deep-seated schist and granite of the Yavapai Supergroup reached the surface. Pebbles eroded from the schist and granite formed a gravel layer above the Paleozoic strata. |
Stage 3: 28-15 Million Years Ago
North of the Central Arizona Highlands, erosion removed rock strata, stripping everything away down to the Hermit Shale. Inch by inch, removal of the easily-eroded, soft shale undermined the harder cliffs above. This caused the overhanging strata to cave in. As this process progressed, a cliff formed, the ancestral Mogollon Rim, and the cliff slowly retreated toward the north. |
Stage 4: 15 Million Years Ago to Present
This most recent stage started with volcanoes and lava flows. These are still visible today at the tops of cliffs near Sedona (red-orange layer on diagram). A little later the Verde Fault, along the west side of the Verde Valley, caused a large lake to form there. This fault also exposed the copper deposits of Jerome. A smaller fault occurred along the future path of Oak Creek Canyon, promoting erosion and development of the canyon. |
Copyright © 2008. All Rights Reserved.