Deborah Painter
Let’s see, once I say “Arizona scorching spots”, what may come to thoughts for many individuals are the eating places, nightclubs and sports activities occasions in Phoenix (the US state’s largest metropolis), the Grand Canyon of the Colorado River, attracting guests from world wide, Tombstone (the notorious “city too robust to die”, the place the equally notorious 1881 gunfight on the OK Corral occurred), and any portion of the desert within the daytime throughout August.
However how many individuals consider the various volcanoes in Arizona USA, a part of a volcanic subject that’s doubtless not completed erupting?
Arizona, USA has seven younger (Quaternary Interval) volcanic fields. The three youngest fields are the San Francisco, Uinkaret and Pinacate volcanic fields. The primary two of those younger fields are on the Colorado Plateau of northern Arizona; the Pinacate Discipline is far farther south on the Arizona-Mexico border.
The San Francisco Discipline is the main focus of this text. It’s located close to Flagstaff and Williams in northern Arizona (Fig. 1). It extends roughly 5,0002km from Williams to the Little Colorado River. There are barely over 600 cones. The sphere was energetic as just lately as 932 BP (Earlier than Current), with the eruption that fashioned Sundown Crater at Sundown Crater Volcano Nationwide Monument.
The spectacular San Francisco Peaks inside this subject are initially a single stratovolcano that skilled deep erosion (Fig. 2). Mount Elden close to Flagstaff is a big volcanic dome, however the majority, together with Sundown Crater, is the ‘strombolian’ sort of cinder cone. Most cinder cones one sees wherever world wide common about 304m in peak. Nonetheless, there are some fairly small ones within the San Francisco Volcanic Discipline averaging 180m excessive and 340m broad. One can not miss them as one travels within the space.
These cinder cones have been quiet for lots of of hundreds and, in some instances, hundreds of thousands of years. Their eruptions had been explosive with gasoline and plumes of lava, however of quick period, as much as however not exceeding a yr for every. The smaller ones are fragile, and a few have already eroded away in just some million years. Many are privately owned and are being mined for his or her volcanic rocks utilized in business and as landscaping stone (Fig. 3).
Are the volcanoes right here prone to erupt once more? May new ones type? The Arizona Geological Survey says “sure”. It has named the realm as a present average geologic hazard, and anticipates that new eruptions will doubtless take the type of a small new cinder cone. When this may occur shouldn’t be identified.
Why are there volcanoes right here?
Arizona shouldn’t be alongside a subduction zone or a spreading zone. Arizona’s volcanic fields are all believed to be located near and above a hot spot in the mantle, since there is a definite eastward trend in the eruptive history. A hot spot is a large plume of mantle material that is more common on the ocean floor than within a continent. Better known continental hot spots in North America are the Yellowstone hot spot and the Snake River Plain hot spot. The motion of the plate (in this case the North American Plate) is west-southwest.
The volcanoes within the San Francisco Volcanic Field are older as one travels from east to west, as is also seen in the Yellowstone and the Snake River Plain hot spots.
The San Francisco Peaks are 3,851m at their highest elevation at Humphreys Peak. They command the scenery for many kilometres and are visible along much of north US 89 and Interstate 40 in the vicinity of Flagstaff and Williams. A stratovolcano is a mountain comprised of layers of basaltic rocks formed from relatively small eruptions of weak, pulsating fountains of lava from a single crater. In the case of Humphreys Peak, this occurred repeatedly over a period of approximately one million years. The last eruption occurred approximately 400,000 years ago. Hikers are attracted to Humphreys Peak, the highest point in Arizona and part of the Humphreys Summit Trail in the Coconino National Forest.
I was fortunate to visit the area on a March day in 2002. I think spring is definitely a good time to see the San Francisco Volcanic Field since the temperatures are pleasant and there might even be some snow. A visit to the San Francisco Volcanic Field would not be complete without a stop in the city of Flagstaff, a starting point on the Arizona side of the Grand Canyon for visitors who want to go there as well.
It is also a good central location for visitors to Wupatki National Monument, Sunset Crater Volcano National Monument, Walnut Canyon National Monument, the Painted Desert, and other sites (Figs. 4 and 5). Buffalo Park is a Flagstaff city park at 2400 North Gemini Road. The telephone number to reach the park staff is (928) 213-2300.
One can picnic under the piñon and ponderosa pines, and enjoy a view of Mount Elden. There are also hiking trails. This volcano, like O’Leary Peak near Sunset Crater, never exploded. Instead, the mountain is composed of layers upon layers of magma that cooled into a dome structure. Some faults allowed the high-silica magma to reach the surface, forming lava ‘lobes’. Mount Elden formed between 6,000 and 5,000 years BP.
Proceeding along US 89 North out of Flagstaff, my friends Terril Shorb, Yvette Schnoeker-Shorb and David Hawk shared with me a pleasant half hour trip of 19km to the Sunset Crater/Wupatki Loop Road. From there, it was three kilometres to Sunset Crater Volcano National Monument, past forests of pines that grow in jagged black basalt that, due to the relatively young age of the basalt and the aridity of the region, appears fresh. In reality, the eruption took place sometime around 932 BP and Native Americans were definitely present in the region at that time to witness it. Archaeologists have found lava from the Bonito Lava Flow at Sunset Crater that had the impression of maize cobs in it. Native Americans had used the cooling lava to cook ears of maize.
The Bonito Lava Flow extends for 3.2km around the base of the volcano and is 30.5m in thickness. The cinder cone itself is off limits to hikers (Fig. 6). It is 2,450m in elevation, taller than most cones in the area, but fragile, showing footprints easily.
In fact, the National Monument came into being because local activists feared for the integrity of the mountain. In 1928, a film production company wanted to place fire pots and set off dynamite within the crater and along its flanks to simulate a volcanic eruption for a motion picture to be named Avalanche. The local activists, led by Harold Colton, the founder of the Museum of Northern Arizona, implored President Herbert Hoover to set aside the volcano and surrounding areas as a National Monument to stop any future attempts at destroying part of the mountain.
Although hiking is not permitted on the volcano, visitors can walk an easy trail from the Visitors Center at 6082 Sunset Crater Road, Flagstaff to an area near the foot of Sunset Crater. The volcano is comprised of basalt with a summit of reddish coloured scoria (Fig. 7), mixed with gypsum, ferrohexahedrite and magnetite.
The last eruption scattered these minerals as a final flourish, hence the name of the mountain. Near the mountain are trails, such as the trail facing nearby O’Leary Peak, a lava dome (Fig. 8). To reach the National Monument by telephone, dial (928) 526-0502. It is best to call first due to occasional fires that could impact travel there.
Another 21.24km to the north on Loop Road is Wupatki National Monument, at 25137 Loop Road, Flagstaff. The telephone number for the Visitors Center is (928) 679-2365. The Visitors Center provides useful information on the town of Wupatki (Fig. 9). The tallest ‘house’ provided about 50 rooms, making homes for approximately 100 people. The red stone bricks comprising the houses are local sandstones known as Moenkopi Sandstone.
When visiting the site, I was struck by the closeness of the basalt and scoria to the structures and wondered “Did the lava flow halt, just missing homes already built or did the lava flow cool and harden and all eruptions cease prior to Native Americans settling the area?” The rangers explained that it was this latter scenario. The ancestors of the modern Zuni and Hopi people built this town over 800 years ago as a focus for their farming and trading.
The ashfall from Sunset Crater’s final eruption made the land around the volcano outside the Bonito Lava Flow very fertile. The people farmed (Fig. 10), hunted (Fig. 11), and traded with people from as far away as what is now modern day Mexico.
These people, from southern climes, introduced the concept of the ball field and a prominent round brick structure was built in a depression within the complex of houses. This was to provide all the traders diversions, recreation and perhaps even opportunities for making wagers.
Eventually, a prolonged drought brought about the end of Wupatki, since the people could no longer grow squash and other crops successfully here. They moved elsewhere with more water and left the town to the elements.
Near Wupatki was so much of that Moenkopi Sandstone in small and highly accessible ridges that I, a hopelessly addicted rock collector, was sorely tempted. I saved myself from potential trouble by telling myself. “No, Debbie, you cannot take them! This is Federal land!”
We took a look at the windblown nearby Painted Desert to the east of Wupatki National Monument as snow clouds gathered dramatically and the March afternoon was drawing to a close.
About the author
Deborah Painter is an ecologist and general environmental scientist. She lives in the United States.
References
Hanson, Sarah. 2009. Sunset Crater, a Cinder Cone Eruption that Impacted the Ancestral Puebloan Indians. Arizona Geology. Arizona Geological Survey: https://azgeology.azgs.arizona.edu/archived_issues/azgs.az.gov/arizona_geology/april09/article_sunsetcratervolcano.html
Hawaiian Volcano Observatory, January 25, 2007. United States Geological Survey. Volcano Watch: San Francisco Volcanic Field, Arizona’s Hotspot: https://www.usgs.gov/observatories/hvo/news/volcano-watch-san-francisco-volcanic-field-arizonas-hotspot
Houk, Rose. October 2, 2009. “America’s Best Idea: Sunset Crater Nearly Destroyed by Hollywood”. KNAU News Talk – Arizona Public Radio: https://www.knau.org/knau-and-arizona-news/2009-10-02/americas-best-idea-sunset-crater-nearly-destroyed-by-hollwyood
Lynch, D. J. September 1982. Volcanic Processes in Arizona. Field Notes of the Arizona Bureau of Geologic and Mineral Technology Volume 12 Number 3 pp. 1-12.
National Park Service Photo Galleries, Sunset Crater Volcano National Monument and Wupatki National Monument.
Rand McNally. 2018. DeLorme’s Arizona Atlas & Gazetteer. Garmin. 68 pages.
Schnoeker-Shorb, Yvette. Personal communication.
Shorb. Terril. Personal communication.
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