Geology of National Parks: Panoramic view of Sonoran Desert plant community and landscape of Organ Pipe Cactus National Monument.

Organ Pipe Cactus National Monument

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Organ Pipe Cactus National Monument is a showcase biosphere -wilderness preserve for the flora and fauna of the Sonoran Desert region within Southern Arizona. The namesake species of Organ Pipe Cactus National Monument is the organ pipe cactus (Stenocereus thurberi). With many slender, curving stems that some believe resemble the pipes of an old-fashioned organ. They are the second-largest columnar cactus in the United States and can grow up to 23 feet tall. They are second only to saguaro cactus (that also grow in abundance in the park) that can grow 40 to 60 feet tall.

The landscape is also showcase for the geologic and tectonic features of the Basin & Range Physiographic Province. The park's mountainous areas provide exposures of Cenozoic-age volcanic rocks (lava flows and tephra deposits of rhyolite, andesite, and basalt composition). These rocks rest unconformable on faulted metamorphic and ignous rocks basement rocks of Precambrian age.

This collection of images includes pictures mostly taken along the Ajo Mountain Drive, a mosly unpaved but maintained one-way loop road that traverses the pediments and foothills below the higher peaks of the Ajo Range to the lowlands of the alluvium-filled Sonoyta Valley. Learn more about the park's amazing geology from the NPS report below.

Organ Pipe Cactus National Monument Geologic Resources Inventory Report: U.S. National Park Service Natural Resource Report NPS/NRSS/GRD/NRR—2022/2399, 102 p. (.pdf file).


Fig. 1 - NPS map of Organ Pipe Cactus National Monument.
Organ Pipe Cactus near Twin Peaks Campground
Fig. 2. Organ Pipe Cactus  		View looking east from Ajo Mountain Wayside parking area of the Ajo Range.
Fig. 3. Ajo Range		 View looking east at the Diablo Mountains part of the Ajo Range from along the Ajo Mountain Drive.
Fig. 4. Ajo Mountain Drive		 Zoom view of a field of saguaro and teddy-bear cholla cactus at the base of the Diablo Mountains part of the Ajo Range along Ajo Mountains Drive.
Fig. 5. Saguaro Cactus
A desert pediments with a field of saguaro cactus.
Fig. 6. Saguaro Cactus 		A Gila Woodpecker and a Crissal Thrasher having a heated discussion while feeding on saguaro cactus flowers.
Fig. 7. Birds on Saguaro 		View from near picnic area along Ajo Mountains Drive of volcanic rock layers exposed in the cliffs of the Diablo Mountains.
Fig. 8. Ajo Mountain Drive 		Zoomed-in view from near picnic area along Ajo Mountains Drive of volcanic rock layers exposed in the cliffs of the Diablo Mountains.
Fig. 9. Diablo Mountains
View of the layered volcanic rocks exposed in the Diablo Mountains from along Ajo Mountain Drive.
Fig. 10. Ajo Mountain Drive		 View looking west down the valley from overlook along Ajo Mountain Drive.
Fig. 11. Ajo Mountain Drive		 View looking east from an overlook along Ajo Mountain Drive of the highland valley and cliffs south of Arch Canyon.
Fig. 12. Diablo Mountains		 Zoom view looking north from along Ajo Mountain Drive of the volcanic plug called Montezumas Head.
Fig. 13. Montezumas Head
View looking northeast from the Ajo Mountain Drive overlook showing Tilloson Peak, a cuesta capped with dark basaltic lava layer.
Fig. 14. Tillotson Peak		 View of Arch Canyon from near the trailhead parking for Arch Canyon along the Ajo Mountain Drive.
Fig. 15. Arch Canyon 		A saguaro "goal post" view of the Arch in Arch Canyon along the Ajo Mountain Drive.
Fig. 16. Arch Canyon 		Zoom view of the arch in Arch Canyon from along Ajo Mountain Drive.
Fig. 17. Arch Canyon Arch
View looking south from a picnic area along the Ajo Mountain Drive looking toward the Diaz Peak (Diz Sprire) mountain area.
Fig. 18. Diaz Spire 		Organ Pipe Cactus, saguaro cactus, and Teddy-Bear cholla on the pediment east of the Ajo Mountains along Ajo Mountain Drive.
Fig. 19. Ajo Mountain Drive 		zoom view looking south from Ajo Mountain Drive toward the Sierra De Santa Rosa (Range that extend across the border into Mexico.
Fig. 20. South toward Mexico 		Organ Pipe Cactus among the campsites in the Twin Peaks Campground.
Fig. 21. Twin Peaks Camp

Fig. 22. Twin Peaks 		View of Pinkley Peak north of the Twin Peaks Campground.
Fig. 23. Pinkley Peak		 Pre-sunrise view looking east from the Twin Peaks Campground.
Fig. 24. Morning camp view 		Zoomed view of the pre-dawn landscape east of the Twin Peaks Campground in Organ Pipe Cactus National Monument.
Fig. 25. Morning camp view

Fig. 26. Panoramic view looking east at the Ajo Range from Ajo Mountain Drive.
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Last modified 5/5/2024.