North-Central Arizona Feature

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Red-Rock Geology

It's hard to imagine that the landlocked desert surrounding Sedona was, for much of prehistoric time, an area of dunes and swamps on the shore of an ancient sea. The ebb and flow of this sea shaped the land. When the sea rose, it planed the dunes before dropping more sediment on top. The process continued for a few hundred million years. Eventually the sediment hardened into gray layers of limestone on top of the red sandstone. When North America collided with another continental plate, the land buckled and lifted, forming the Rocky Mountains and raising northern Arizona thousands of feet. Volcanoes erupted in the area, capping some of the rock with erosion-resistant basalt.

Oak Creek started flowing at this time, eroding through the layers of sandstone and limestone. Along with other forces of erosion, the creek carved out the canyons and shaped the buttes. Sedona's buttes stayed intact because a resilient layer of lava had hardened on top and slowed the erosion process considerably. As iron minerals in the sandstone were gradually exposed to the elements, they turned red in a process similar to rusting. The iron minerals, in turn, stained the surrounding colorless quartz and grains of sand—it only takes 2% red-iron material to give the sandstone its red color.

Like the rings of a tree, the striations in the rock document the passage of time and the events: limestone marking the rise of the sea, sandstone indicating when the region was coastline.

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