![]() ![]() These future eruptions may provide spectacular volcanic displays but should pose little hazard because of their small size and the relative remoteness of the area.Ī volcano is an opening where magma erupts onto the surface as lava after rising from deep within the Earth. Geological Survey (USGS) scientists believe that the most probable sites of future eruptions are in the eastern part of the field and that the eruptions are likely to be small. With an average interval of several thousand years between past periods of volcanic activity, it is impossible to forecast when the next eruption will occur. Today, this belt of volcanoes extends about 50 miles from west to east.Īlthough there has been no eruption for nearly 1,000 years, it is likely that eruptions will occur again in the San Francisco Volcanic Field. Subsequently, a several-mile-wide belt of successively younger eruptions migrated eastward, to the area of modern Flagstaff, and even a bit beyond, toward the valley of the Little Colorado River. The first volcanoes in the San Francisco Volcanic Field began to erupt about 6 million years ago, in an area where the town of Williams is now. As the North American Plate moves slowly westward over this stationary source of molten rock (magma), eruptions produce volcanoes that are strung out progressively eastward. Some geologists suggest that there is a site of localized melting, or hot spot, fixed deep within the Earths mantle beneath northern Arizona. Why does Northern Arizona have so many geologically young volcanoes? Most volcanoes are located near boundaries of the Earths tectonic plates, but Arizona is well within the interior of the North American Plate. Instead, the area includes both Arizonas highest mountainSan Francisco Mountain, with peaks rising to 12,633 feetand the States youngest volcanoSunset Crater, which erupted less than 1,000 years ago and has been a National Monument since 1930. Without the volcanoes, this region would be a flat, arid plateau. Flagstaff lies at the south-central edge of the volcanic field nestled between the base of Elden Mountain and the Observatory Mesa flow emitted from A-1 Mountain.Īlmost all hills and mountains between Flagstaff and the Grand Canyon are geologically young but extinct volcanoes of the San Francisco Volcanic Field. Larger tectonic structures such as the northeast-trending Mesa Butte Fault and Doney Fault are also seen. Some lava flows (flat lobate features) are easily recognized by their proximity to vents. This digital elevation model (DEM) of the San Francisco Volcanic Field shows many of the more than 600 vents which have erupted in the area during the past 6 million years. (Copyrighted photo courtesy of Michael Collier.) San Francisco Mountain and Sunset Crater are only two of the hundreds of volcanoes in the San Francisco Volcanic Field, which covers about 1,800 square miles of northern Arizona. The ancient inhabitants of this area must have witnessed the eruption of nearby Sunset Crater, the States youngest volcano, which erupted in about A.D. The peaks of San Francisco Mountain, an eroded stratovolcanowhich includes Arizonas highest point, Humphreys Peak at 12,633 feettower over the ruins of an ancient Native American pueblo in Wupatki National Monument. The varied forests and geologic features of the San Francisco Volcanic Field offer diverse recreational opportunities, including camping, hiking, mountain biking, wildlife viewing, and winter sports. Forest life zones in the region range from Piñon-Juniper at lower elevations through Ponderosa Pine to Fir and Bristlecone Pine at the highest elevations. Much of the field lies within Coconino and Kaibab National Forests. The San Francisco Volcanic Field, which covers about 1,800 square miles, is part of northern Arizonas spectacular landscape. The most prominent landmark is San Francisco Mountain, a stratovolcano that rises to 12,633 feet and serves as a scenic backdrop to the city of Flagstaff. Their activity has created a topographically varied landscape with forests that extend from the Piñon-Juniper up to the Bristlecone Pine life zones. During its 6-million-year history, this field has produced more than 600 volcanoes. Stauffer Northern Arizonas San Francisco Volcanic Field, much of which lies within Coconino and Kaibab National Forests, is an area of young volcanoes along the southern margin of the Colorado Plateau. The San Francisco Volcanic Field, Arizona The San Francisco Volcanic Field, Arizona | USGS Fact Sheet 017-01
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