The border roads remain closed (the dirt roads directly along the border and all crossover roads leading from South Puerto Blanco Drive to the border) to all public vehicle and pedestrian traffic for public safety. South Puerto Blanco Drive remains open.
Gachado Line Camp open. Southeast border road and access roads closed
El Camino De Dos Republicas remains open from SR85 to Gachado Line Camp. Dos Lomitas is not accessible. The southeast border road from Lukeville Port of Entry eastward to the Santa Rosa Mountains is closed to public vehicle and pedestrian traffic.
Mountains like this one are fairly young in the grand scheme of things. The mountains in this monument formed from volcanoes. Those volcanoes rose from the ground as the earth churned uneasily underneath.
NPS photo
The study of the materials that make up the Earth is called geology. North America has fascinating geological formations that have been forming and changing for millions of years. Though this may sound like a long time, on the geological scale, it is a blink of an eye!
Imagine all of Earth’s geologic time placed evenly over a clock, with noon (12pm) marking the formation of Earth, and midnight (12am) marking the present. The North American continent only formed within the last 3-5 minutes (200-30 million years ago). Humans have only been around for the last fraction of a second before midnight (in reality, modern humans appeared around 350,000 years ago).
Learn more about the geologic history of Organ Pipe Cactus as you explore this page. If you want to explore more about the geologic history of the Sonoran Desert or learn more about geology across the United States, visit the geologic history of Organ Pipe Cactus and Geoscience Concepts page.
A general schematic of Basin and Range formation. The Farallon Plate moving to the right, being subducted under the North American Plate, moving to the left. Bubbling and thinning of the crust facilitated volcanic formations. To the right, signature crumpling of the surface occurs.
NPS Image
Basin and Range
Organ Pipe Cactus National Monument occupies a small part of the massive area called the Basin and Range Province. This region stretches from its eastern boundary in West Texas to its western boundary at the foothills of the Sierra Nevada range in California. It spans from deep western Mexico in the south to southern Oregon and Idaho in the north. The Basin and Range Province crosses almost every ecosystem imaginable, from wetland to desert, from forest to tundra, and from beaches to mountains, but it is unified by its unique geology.
A Time of Unrest
Between 80 and 30 million years ago, the continents that we know today were drifting into their modern places, but things looked very different. What would become Nevada and Arizona sat closer to the Pacific coast. Pieces of Earth’s crust called tectonic plates were busy dragging themselves into and out of the layer of Earth beneath them (the mantle). The Farallon Plate was an ancient piece of crust that lived under the Pacific Ocean. The east bound Farallon Plate collided with the edge of the west bound North American Plate and began slipping into the Earth through a process called subduction.
The Farallon Plate first made a deep dive under the North American Plate, then leveled out like a spatula under pizza. The plates kept moving east and west, creating pressure that squished and crumpled the western part of the North American Plate. As the North American Plate scraped over the Farallon Plate, crust swelled under it to create a massive area of highlands along the continent’s western edge. During this squishing and swelling, weak spots or “faults” formed where brittle rock split, exposing deeper, harder rock. As the Farallon Plate melted in the Earth, magma rose to the surface, creating volcanoes.
A Time of Ease
Eventually, the Farallon Plate was all but swallowed by the Earth (with a couple remnants) and the North American plate could relax. The crust began to spread and thin out, and the western highlands caved in, creating the repeating pattern of mountains and valleys that span western North America. Imagine playing an accordion, compressing it, then slowly pulling it apart. The ridges of the accordion are like the mountains and the spaces between are valleys.
After the Farallon Plate (dark green) was subducted, the hot mantle (light green) facilitated spreading of the North American Plate (orange), creating distinct valleys and mountains that are visible today, alongside remnants of volcanoes.
Modified from “Beauty from the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest,” by Robert J. Lillie, Wells Creek Publishers, 92 pp., 2015, www.amazon.com/dp/1512211893.
From Then to Now
The valleys, of course, became the “basins,” and the mountains became the “ranges,” giving this area of North America its name. The climate and environment at the top of these mountains are often very different from those in the valleys. These high elevation environments, or “sky islands” stretch across the Basin and Range Province, isolated from each other by the basins between.
Ecosystems are further isolated from each other by rivers and streams. As the valleys formed in long lines, rivers that formed in them would rarely connect, and often had no outlet. Over time, rivers carried sediment, salt, and other loose objects and animals downstream, where the river would eventually end in salt flats or sand dunes. The Quitobaquito pupfish and Sonoyta mud turtle were stranded by this form of isolation and left to adapt to their local surroundings at Quitobaquito Springs.
Geologic History and Current Events of Basin and Range Providence
Locations:Big Bend National Park, Death Valley National Park, Dinosaur National Monument, Glacier National Park, Glen Canyon National Recreation Area, Grand Canyon National Park, Great Basin National Park, Lake Mead National Recreation Area, Santa Monica Mountains National Recreation Area, Tule Springs Fossil Beds National Monumentmore »
All across the park system, scientists, rangers, and interpreters are engaged in the important work of studying, protecting, and sharing our rich fossil heritage. Park Paleontology news provides a close up look at the important work of caring for these irreplaceable resources.
Contribute to Park Paleontology News by contacting the newsletter editor
Locations:Big Bend National Park, Dinosaur National Monument, Grand Canyon National Park
Offices:Geologic Resources Division
During the 1930s, public works programs helped uncover paleontological resources at numerous parks. Projects at Big Bend National Park, Dinosaur National Monument, the former Fossil Cycad National Monument, and Grand Canyon National Park are highlighted here from the many stories.
Currently, there is no standardization for paleontological resource information between park units. To address this, the Intermountain Regional Office, the NPS Paleontology Program, and Glen Canyon National Recreation Area have been working to develop a database to manage geospatial information.
Big Bend National Park preserves an important fossil record spanning the Cretaceous / Paleogene boundary. Both marine and terrestrial strata preserve a diversity of vertebrates, invertebrates, plants and trace fossils. A recent inventory of NPS fossil plants from across the national parks includes the important fossil record of flora from Big Bend National Park.
Locations:Death Valley National Park, Great Basin National Park, Lake Mead National Recreation Area, Santa Monica Mountains National Recreation Area, Tule Springs Fossil Beds National Monument
Offices:Geologic Resources Division
This year, for the first time, the NPS hired a shared paleontologist to support multiple parks in the same region. Dr. Aubrey Bonde was selected as the Southern Network Paleontologist to support five parks throughout Southern Nevada and California.
Locations:Aniakchak National Monument & Preserve, Arches National Park, Big Bend National Park, Bighorn Canyon National Recreation Area, Bryce Canyon National Park, Canyonlands National Park, Capitol Reef National Park, Chaco Culture National Historical Park, Colorado National Monument, Curecanti National Recreation Area, Denali National Park & Preserve, Dinosaur National Monument, Gettysburg National Military Park, Glen Canyon National Recreation Area, Katmai National Park & Preserve, Lewis and Clark National Historical Park, Mesa Verde National Park, Navajo National Monument, Petrified Forest National Park, Pipe Spring National Monument, Rainbow Bridge National Monument, Springfield Armory National Historic Site, Valley Forge National Historical Park, Wrangell - St Elias National Park & Preserve, Yellowstone National Park, Yukon - Charley Rivers National Preserve, Zion National Parkmore »
Offices:Geologic Resources Division
Dinosaur fossils have been discovered at or are associated with at least 27 NPS units. Geographically, their finds are concentrated in the parks of the Colorado Plateau, but they have been found from central Alaska to Big Bend National Park in Texas to Springfield Armory National Historic Site in Massachusetts. The most famous site is the Dinosaur Quarry of Dinosaur National Monument, but a rush of new finds since the 1970s has greatly expanded our knowledge.
Each park-specific page in the NPS Geodiversity Atlas provides basic information on the significant geologic features and processes occurring in the park. Links to products from Baseline Geologic and Soil Resources Inventories provide access to maps and reports.
Each park-specific page in the NPS Geodiversity Atlas provides basic information on the significant geologic features and processes occurring in the park.
Each park-specific page in the NPS Geodiversity Atlas provides basic information on the significant geologic features and processes occurring in the park. Links to products from Baseline Geologic and Soil Resources Inventories provide access to maps and reports.
Each park-specific page in the NPS Geodiversity Atlas provides basic information on the significant geologic features and processes occurring in the park.
