The Arizona Geological Survey has made available for free download an new report on alluvial fans near the Phoenix area. The report shows how development on the fans fared.
The full report may be downloaded here. The report contains many photos from pre-development through developed stage.
Here is a summary from AZGS:
Flooding issues and drainage problems associated with historical development on four active alluvial fan study sites in central Arizona were examined to document the effectiveness of engineered flood protection measures and floodplain management policies. The study sites are located in the metropolitan Phoenix area and include (1) Ahwatukee-City of Phoenix, (2) Pima Canyon-City of Phoenix/Guadalupe, (3) Reata Pass-Scottsdale, and (4) Lost Dog-Scottsdale. The four study sites have experienced different types of urbanization, including master-planned communities, single lot residential development, public transportation and utility networks, and major engineered drainage structures such as channels, detention basins, culverts, and dams. The engineered drainage systems at the four historical alluvial fan study sites have performed adequately during the 30-year period of record, at least with respect to controlling the flow path uncertainty and sedimentation normally associated with active alluvial fans. Significantly, no homes have been damaged by alluvial fan flooding at any of the study sites, and no avulsions* have occurred in the developed portions of the alluvial fans. Two floods exceeding the 100-year design storm occurred on two of the fans, but many of the flood control measures on the other fan sites remain untested by large floods. The absence of flood damages is likely due to lack of debris flow potential at any of the sites, low rates of sediment yield at the fan sites, channelization and encroachment that increase sediment transport off the fan surface, and to some degree, the relatively short period of record since development first occurred.
*Avulsions: An abrupt change in the course of a stream that forms the boundary between two parcels of land resulting in the loss of part of the land of one landowner and a consequent increase in the land of another.
Check the Article Index page for more stories of Arizona geology.
Organic nitrogen compounds such as ammonia (NH3) act as plant fertilizers. Robust plant growth consumes more atmospheric carbon dioxide during the process of photosynthesis. However, atmospheric nitrogen (N2) is relatively inert. It is converted to organic nitrogen compounds by bacteria in the top soil layers. (See nitrogen fixation) Climate models have assumed that the atmosphere is the only source of nitrogen and have therefore underestimated its fertilization effect and also underestimated the capability of plants to remove carbon dioxide from the atmosphere. New studies show that much nitrogen comes from rocks, some already in useable organic form. Weathering of rocks releases this organic nitrogen.
“A considerable amount of the nitrogen in igneous and sedimentary rocks exists as ammonium ions held within the lattice structures of silicate minerals. In sedimentary rocks, the ammonium is held by secondary silicate minerals; in igneous rocks, the ammonium is contained largely within potassium-bearing primary minerals. Analyses indicated that most of the nitrogen in igneous rocks, and from one-tenth to two-thirds of that in sedimentary rocks (shales) occurred as fixed ammonium.” (Source)
Nitrate deposits in arid and semi-arid regions provide another source of nitrogen.
“Nitrogen bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification. Nitrogen in rock originates as organically bound nitrogen associated with sediment, or in thermal waters representing a mixture of sedimentary, mantle, and meteoric sources of nitrogen.” (Source)
A new study, reported by Science Daily, concerns research conducted by University of California – Davis published April 6, 2018.
“For centuries, the prevailing science has indicated that all of the nitrogen on Earth available to plants comes from the atmosphere. But a study from the University of California, Davis, indicates that more than a quarter comes from Earth’s bedrock.”
“The discovery could greatly improve climate change projections, which rely on understanding the carbon cycle. This newly identified source of nitrogen could also feed the carbon cycle on land, allowing ecosystems to pull more emissions out of the atmosphere, the authors said.”
“Geology might have a huge control over which systems can take up carbon dioxide and which ones don’t.”
“While there were hints that plants could use rock-derived nitrogen, this discovery shatters the paradigm that the ultimate source of available nitrogen is the atmosphere. Nitrogen is both the most important limiting nutrient on Earth and a dangerous pollutant, so it is important to understand the natural controls on its supply and demand. Humanity currently depends on atmospheric nitrogen to produce enough fertilizer to maintain world food supply. A discovery of this magnitude will open up a new era of research on this essential nutrient.”
Study citation: B. Z. Houlton, S. L. Morford, R. A. Dahlgren. Convergent evidence for widespread rock nitrogen sources in Earth’s surface environment. Science, 2018; 360 (6384): 58 DOI: 10.1126/science.aan4399.
Looks like “climate science” is still not settled. For instance, a 2003 study published in the same Science journal claimed, “there will not be enough nitrogen available to sustain the high carbon uptake scenarios.” Investor’s Business Daily opines: “with more nitrogen available, plant life might be able to absorb more CO2 than climate scientists have been estimating, which means the planet won’t warm as much, despite mankind’s pumping CO2 into the atmosphere.”
The town of Jerome roosts on the slopes of Cleopatra Hill in Yavapai County, Arizona; and is steeped in a rich history of copper, zinc, gold, and silver ore mining from an ancient volcanogenic massive sulfide deposit that formed on a sea floor more than 1.74 billion years ago.
Author, geologist, and mining historian David Briggs’ new contributed report, ‘History of the Verde Mining District, Jerome, Arizona’, reviews the mining history of Jerome from the Spanish discovery of copper in A.D. 1583 at what is now the United Verde Mine site to recent remediation efforts of Freeport McMoRan c. 2010.
The United Verde Mine was the most prolific producer in the district. Between 1883 and 1975 it produced nearly 3 billion pounds of copper; 52 million pounds of zinc; 1.3 million troy oz. of gold; and 48.3 million troy Oz. of silver.
Snapshot of the geology of the United Verde Mining District. The oldest stratigraphic units exposed in the Verde Mining District are a part of the early Proterozoic Ash Creek Group, which is characterized by at least two mafic to felsic cycles of largely submarine volcanics that are stratigraphically overlain by a thick sequence of volcaniclastic sediments deposited along the steep slopes of an ancient intraoceanic island arc (Anderson, 1989 and Gustin, 1988). Evidence for subaqueous deposition of these units is supported by the presence of pillow basalts and hyaloclastitic (quench) textures, presence of black-smoker-type massive sulfide and exhalative chert, and turbidites and textures suggesting soft sediment deformation (Lindholm, 1991). The Ash Creek Group was deposited in a deep water oceanic environment, which is similar to the Izu-Bonin-Mariana arc, a modern day analog located in the western Pacific Ocean (D. Briggs, 2018).
High-grade ore -10-20% copper – was transported directly to the Jerome smelter, while low-grade ore was first treated on the hillslope by heap roasting with cordwood; a practice that undoubtedly reduced air quality.
By 1922, the economy of mining and falling ore grade caused the United Verde mine to begin open pit mining to complement ongoing underground workings.
Mine fires plagued the United Verde operation, killing miners, caving ground, hampering production and causing the 1,000-foot No.2 shaft to be abandoned. Efforts to extinguish the mine fires using water or carbon dioxide failed because there was no way to prevent oxygen from filtering into the burn area. Uncontrolled burning of underground ore seams would at times fill the open pit with dense smoke.
The roles of James Douglas, Eugene Jerome, James Thomas and William Andrews Clark in establishing the United Mine Verde Mine and the towns of Jerome and Clarksdale are described in detail.
By 1920, the Jerome mining camp was a polyglot village with more than 20 nationalities, including: Americans, Chinese, Irish, Italian, Mexican, and people of Slavic origin. Life in the camp was primitive, austere, and the air, water, environment and sanitary conditions were degraded by smelting ore and deforestation of the surrounding Black Hills. Labor problems during WW1 were managed by forcing the ringleaders into cattle cars and marooning them in the Mojave Desert outside Needles, California.
By the 1950s, ore production was falling, forcing those living in Jerome to slowly transition from mining to a small but burgeoning tourism economy. The Jerome Historical Society, founded in 1953, worked with the local mine companies, business leaders, and the community to strategize a move from mining to tourism bolstered by artisans and craftsman.
In the final section of this exemplary history, the author revisits recent reclamation efforts and explores the future of mining in the Verde mining district.
Climate alarmists have long been predicting that global warming induced sea level rise would make low-lying Pacific islands disappear and cause thousands of “climate refugees” to seek new homes. Here are some examples:
Smithsonian.com, August, 2004: Will Tuvalu Disappear Beneath the Sea? Global warming threatens to swamp a small island nation.
Mother Jones, December, 2009: What Happens When Your Country Drowns?
Washington Post, August, 2014: Has the era of the ‘climate change refugee’ begun?
Bloomberg, November, 2017: A Tiny Island Prepares the World for a Climate Refugee Crisis.
These alarmist claims have not come to pass because of the geologic processes that build these islands.
A new paper published in Nature Communications on Feb. 9, 2018, shows that despite sea level rise, most islands are increasing in land area.
A University of Auckland study (Patterns of island change and persistence offer alternate adaptation pathways for atoll nations, Paul S. Kench, Murray R. Ford & Susan D. Owen) examined changes in the geography of Tuvalu’s nine atolls and 101 reef islands between 1971 and 2014, using aerial photographs and satellite imagery. The paper claims that local sea level has risen at twice the global average (~3.90 + 0.4 mm.yr-1). That translates to about six inches over the 43-year period. However, the study found eight of the atolls and almost three-quarters of the islands grew during the study period, increasing Tuvalu’s total land area by 2.9 percent, even though sea levels in the country rose at twice the global average. (Read Full paper in Nature).
Here is figure 3 from that paper followed by its caption:
Caption for Tuvalu fig 3 (ha = hectares): Examples of island change and dynamics in Tuvalu from 1971 to 2014.
A Nanumaga reef platform island (301 ha) increased in area 4.7 ha (1.6%) and remained stable on its reef platform.
B Fangaia island (22.4 ha), Nukulaelae atoll, increased in area 3.1 ha (13.7%) and remained stable on reef rim.
C Fenualango island (14.1 ha), Nukulaelae atoll rim, increased in area 2.3 ha (16%). Note smaller island on left Teafuafatu (0.29 ha), which reduced in area 0.15 ha (49%) and had significant lagoonward movement.
D Two smaller reef islands on Nukulaelae reef rim. Tapuaelani island, (0.19 ha) top left, increased in area 0.21 ha (113%) and migrated lagoonward. Kalilaia island, (0.52 ha) bottom right, reduced in area 0.45 ha (85%) migrating substantially lagoonward.
E Teafuone island (1.37 ha) Nukufetau atoll, increased in area 0.04 ha (3%). Note lateral migration of island along reef platform. Yellow lines represent the 1971 shoreline, blue lines represent the 1984 shoreline, green lines represent the 2006 shoreline and red lines represent the 2014 shoreline.
The reason that these islands are gaining area is that as the sea rises, coral reefs grow higher and trap coral debris and sand to build up the island. The science of coral reef atolls is not new. This process was first described by Charles Darwin in 1842: The structure and distribution of coral reefs. Being the first part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836. London: Smith Elder and Co. (Link to Darwin’s full description).
This figure from Darwin’s paper shows that coral atolls originate around a volcanic island or seamount. As sea level rises (or land sinks) the corals grow to remain in shallow water and the coral debris and sand cause an atoll island to form. That the corals were able to overcome a recent six-inch rise in sea level may not seem very much, but remember that these islands have been around a long time and dealt with a 400-foot rise in sea level since the depths of the last glacial epoch.
The findings of the new paper cited above support previous studies. For instance:
Kench et al., 2015, Coral islands defy sea-level rise over the past century: Records from a central Pacific atoll, Geological Society of America, in Geology Magazine, March 2015. (Source)
“Funafuti Atoll, in the tropical Pacific Ocean, has experienced some of the highest rates of sea-level rise (~5.1 + 0.7 mm/yr), totaling ~0.30 + 0.04 m over the past 60 yr. We analyzed six time slices of shoreline position over the past 118 yr at 29 islands of Funafuti Atoll to determine their physical response to recent sea-level rise. Despite the magnitude of this rise, no islands have been lost, the majority have enlarged, and there has been a 7.3% increase in net island area over the past century (A.D. 1897–2013). There is no evidence of heightened erosion over the past half-century as sea-level rise accelerated. Reef islands in Funafuti continually adjust their size, shape, and position in response to variations in boundary conditions, including storms, sediment supply, as well as sea level. Results suggest a more optimistic prognosis for the habitability of atoll nations and demonstrate the importance of resolving recent rates and styles of island change to inform adaptation strategies.”
UPDATE: A new paper published 19 September 2018 finds:
Over the past decades, atoll islands exhibited no widespread sign of physical destabilization
in the face of sea-level rise. A reanalysis of available data, which cover
30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost
land area and that 88.6% of islands were either stable or increased in area, while
only 11.4% contracted. Atoll islands affected by rapid sea-level rise did not show a
distinct behavior compared to islands on other atolls. Island behavior correlated
with island size, and no island smaller than 10 ha decreased in size. This threshold
could be used to define the minimum island size required for human occupancy
and to assess atoll countries and territories’ vulnerability to climate change. Beyond
emphasizing the major role of climate drivers in causing substantial changes in the
configuration of islands, this reanalysis of available data indicates that these drivers
explain subregional variations in atoll behavior and within-atoll variations in island
and shoreline (lagoon vs. ocean) behavior, following atoll-specific patterns.
Increasing human disturbances, especially land reclamation and human structure
construction, operated on atoll-to-shoreline spatial scales, explaining marked
within-atoll variations in island and shoreline behavior. Collectively, these findings
highlight the heterogeneity of atoll situations. Further research needs include
addressing geographical gaps (Indian Ocean, Caribbean, north-western Pacific
atolls), using standardized protocols to allow comparative analyses of island and
shoreline behavior across ocean regions, investigating the role of ecological
drivers, and promoting interdisciplinary approaches. Such efforts would assist in
anticipating potential future changes in the contributions and interactions of key
drivers. Read paper: http://sci-hub.tw/10.1002/wcc.557
The U.S. Geological Survey has just released its annual summary of non-fuel mineral production in the U.S. for 2017. The estimated total value of domestically-mined, non-fuel minerals in the United States was $75.2 billion, a 6% increase from 2016.
The estimated value of metals production increased 12% to $26.3 billion. Principal contributors to the total value of metal mine production in 2017 were gold (38%), copper (30%), iron ore (12%), and zinc (8%).
The total value of industrial minerals production was $48.9 billion, a 3% increase from that of 2016. The main industrial minerals were crushed stone (31%), cement (20%), and construction sand and gravel (16%).
These mineral materials were, in turn, consumed by downstream industries to produce an estimated value of $2.94 trillion for the U.S. economy in 2017, a 3.5% increase from 2016. If you add in manufacturing which uses imported mineral products as well, the value of non-fuel minerals to the U.S. gross domestic product was $19.3 trillion in 2017.
Nevada captured first place in U.S. non-fuel mineral mining in 2017 with a production value of $8.68 billion, mainly from Gold.
Arizona was the second largest producer with a production value of $6.61, mainly from copper. Mike Conway of the Arizona Geological Survey summed up the Arizona 2017 highlights as follows:
1st in copper production with ~ 68% of domestic production.
2nd in gemstone production after Oregon and ahead of Idaho.
5th in producing sand and gravel for construction.
Other industrial minerals produced in Arizona in 2017: gypsum, dimension stone, clay, zeolites, bentonite, perlite, and salt.
6th in production of zeolites, and the only producer of chabazite.
Arizona joins six other states involved in helium production.
Arizona is one of five states with molybdenum production.
Arizona is a leader in Rhenium production with four of the six operations in the U.S.
The U.S. Geological Survey notes:
In 2017, U.S. production of 13 mineral commodities was valued at more than $1 billion each. These were, in decreasing order of value, crushed stone, gold, cement, copper, construction sand and gravel, industrial sand and gravel, iron ore, lime, zinc, phosphate rock, salt, soda ash, and clays (all types).
In 2017, 11 States each produced more than $2 billion worth of nonfuel mineral commodities. These States were, in descending order of production value, Nevada, Arizona, Texas, Alaska, California, Minnesota, Florida, Utah, Missouri, Michigan, and Wyoming.
The US Geological Survey report shows that the U.S. is 100% reliant on imports for 22 minerals.
A note on reserves and resources from the U.S. Geological Survey:
Reserves data are dynamic. They may be reduced as ore is mined and (or) the feasibility of extraction diminishes, or more commonly, they may continue to increase as additional deposits (known or recently discovered) are developed, or currently exploited deposits are more thoroughly explored and (or) new technology or economic variables improve their economic feasibility. Reserves may be considered a working inventory of mining companies’ supplies of an economically extractable mineral commodity. As such, the magnitude of that inventory is necessarily limited by many considerations, including cost of drilling, taxes, price of the mineral commodity being mined, and the demand for it. Reserves will be developed to the point of business needs and geologic limitations of economic ore grade and tonnage. For example, in 1970, identified and undiscovered world copper resources were estimated to contain 1.6 billion metric tons of copper, with reserves of about 280 million tons of copper. Since then, almost 520 million tons of copper have been produced worldwide, but world copper reserves in 2017 were estimated to be 790 million tons of copper, more than double those of 1970, despite the depletion by mining of more than the original estimated reserves.
Future supplies of minerals will come from reserves and other identified resources, currently undiscovered resources in deposits that will be discovered in the future, and material that will be recycled from current in use stocks of minerals or from minerals in waste disposal sites. Undiscovered deposits of minerals constitute an important consideration in assessing future supplies.
You can read the entire 200-page report, MINERAL COMMODITY SUMMARIES 2018, at
The US Department of Energy’s National Energy Technology Laboratory (NETL) has identified high concentrations of rare earth elements (REE) in coal samples collected from several American coal basins and is doing research to see if these minerals are economically recoverable.
were collected from the Illinois, Northern Appalachian, Central Appalachian, Rocky Mountain Coal Basins, and the Pennsylvania Anthracite regions. The samples were found to have high REE concentrations greater than 300 parts per million (ppm).
NETL said: “Concentrations of rare earths at 300ppm are integral to the commercial viability of extracting REE from coal and coal by-products, making NETL’s finding particularly significant in the effort to develop economical domestic supplies of these elements.”
NETL has partnered with West Virginia University (WVU), the University of Kentucky (UK), Tetra Tech, and the XLight for the research project.
The current difficulties and high expenses associated with REE extraction has left the U.S. dependent on foreign REE imports. Currently, China supplies about 90 percent of REE used in industry.
Rare earth elements are vital to modern society. Some of the uses include computer memory, DVDs, rechargeable batteries, cell phones, catalytic converters, magnets, fluorescent lighting, night-vision goggles, precision-guided weapons, communications equipment, GPS equipment, batteries, and other defense electronics.
There are 17 naturally occurring rare earth elements: yttrium, scandium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
Despite the name “rare earths” the more common REE are each similar in crustal abundance to commonplace metals such as chromium, nickel, copper, zinc, molybdenum, tin, tungsten, and lead, but REE rarely occur in economic concentrations, and that’s the problem.
The U.S. used to be self-sufficient in REE due to one deposit, Mountain Pass in the Mojave desert, California, just west of Las Vegas, Nevada. That mine, a carbonatiteintrusion with extraordinary contents of light REE (8 to 12% rare earth oxides) was discovered in 1949 and began production in 1952. Mining ceased in 2002 due to low prices and some environmental regulatory trouble triggered by a tailings spill. However, the mine was reactivated in 2012 but went bankrupt in 2016. Another company (a Chinese consortium) purchased the property in July, 2017, and is working to restart operations.
Some other U.S. rare earth resources are shown on the map below.
See a power-point essay on REE that explains geology, deposit types, and many more details.
One of the authors of that power-point says:
“For example, a typical coal contains 62 parts per million (ppm) of total rare earth elements on a whole sample basis. With more than 275 billion tons of coal reserves in the United States, approximately 17 million tons of rare earth elements are present within the coal—that’s a 1,000-year supply at the current rate of consumption.” —Dr. Evan Granite, NETL
The report also says that abandoned tailings piles from coal and iron mines may be important resources of REE.
Dr. Granite says that the United States consumes around 16- to17 thousand tons of REE each year, and this demand could be completely satisfied by extracting rare earths from domestic coal and coal by-products.
The US Geological Survey has just published Field-trip guides to selected volcanoes and volcanic landscapes of the western United States Scientific Investigations Report 2017-5022. Links to separate chapters are found at https://pubs.er.usgs.gov/publication/sir20175022
The North American Cordillera is home to a greater diversity of volcanic provinces than any comparably sized region in the world. The interplay between changing plate-margin interactions, tectonic complexity, intra-crustal magma differentiation, and mantle melting have resulted in a wealth of volcanic landscapes. Field trips in this guide book collection (published as USGS Scientific Investigations Report 2017–5022) visit many of these landscapes, including (1) active subduction-related arc volcanoes in the Cascade Range; (2) flood basalts of the Columbia Plateau; (3) bimodal volcanism of the Snake River Plain-Yellowstone volcanic system; (4) some of the world’s largest known ignimbrites from southern Utah, central Colorado, and northern Nevada; (5) extension-related volcanism in the Rio Grande Rift and Basin and Range Province; and (6) the eastern Sierra Nevada featuring Long Valley Caldera and the iconic Bishop Tuff. Some of the field trips focus on volcanic eruptive and emplacement processes, calling attention to the fact that the western United States provides opportunities to examine a wide range of volcanological phenomena at many scales.
The 2017 Scientific Assembly of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) in Portland, Oregon, was the impetus to update field guides for many of the volcanoes in the Cascades Arc, as well as publish new guides for numerous volcanic provinces and features of the North American Cordillera. This collection of guidebooks summarizes decades of advances in understanding of magmatic and tectonic processes of volcanic western North America.
These field guides are intended for future generations of scientists and the general public as introductions to these fascinating areas; the hope is that the general public will be enticed toward further exploration and that scientists will pursue further field-based research.
The U.S. Geological Survey has just published a new assessment of mineral resources vital to our modern economy: Critical mineral resources of the United States—Economic and environmental geology and prospects for future supply, Professional Paper 1802
Edited by:Klaus J. Schulz , John H. DeYoung Jr. , Robert R. Seal II , and Dwight C. Bradley
You can download the entire book (148 Mb) and/or individual chapters here:
The book consists of two introductory chapters and 20 chapters which each discuss the geology, mineralogy, and occurrence of specific mineral commodities. Note that the U.S. is entirely dependent on imports for 20 critical minerals (see page 6 of this publication for a chart:https://minerals.usgs.gov/minerals/pubs/mcs/2017/mcs2017.pdf )
The following map from PP1802 shows where the U.S. gets minerals for which we are at least 50 percent dependent on imports.
The first chapter in PP1802 justifies the need for this report as follows:
The global demand for mineral commodities is at an all time high and is expected to continue to increase, and the development of new technologies and products has led to the use of a greater number of mineral commodities in increasing quantities to the point that, today, essentially all naturally occurring elements have several significant industrial uses. Although most mineral commodities are present in sufficient amounts in the earth to provide adequate supplies for many years to come, their availability can be affected by such factors as social constraints, politics, laws, environmental regulations, land-use restrictions, economics, and infrastructure.
This volume presents updated reviews of 23 mineral commodities and commodity groups viewed as critical to a broad range of existing and emerging technologies, renewable energy, and national security. The commodities or commodity groups included are antimony, barite, beryllium, cobalt, fluorine, gallium, germanium, graphite, hafnium, indium, lithium, manganese, niobium, platinum-group elements, rare-earth elements, rhenium, selenium, tantalum, tellurium, tin, titanium, vanadium, and zirconium. All these commodities have been listed as critical and (or) strategic in one or more of the recent studies based on assessed likelihood of supply interruption and the possible cost of such a disruption to the assessor. For some of the minerals, current production is limited to only one or a few countries. For many, the United States currently has no mine production or any significant identified resources and is largely dependent on imports to meet its needs. As a result, the emphasis in this volume is on the global distribution and availability of each mineral commodity. The environmental issues related to production of each mineral commodity, including current mitigation and remediation approaches to deal with these challenges, are also addressed.
This article notes: The value of all non-fuel minerals produced from U.S. mines was $74.6 billion, a slight increase over production in 2015. “ Domestic raw materials and domestically recycled materials were used to process mineral materials worth $675 billion. These mineral materials were, in turn, consumed by downstream industries with an estimated value of $2.78 trillion in 2016.” Nevada was ranked first with a total mineral production value of $7.65 billion, mainly from gold. Arizona came in second in total production with a value of $5.56 billion and first in U.S. copper production.
Phil Anderson (Ph.D., University of Arizona) had a genius for mapping and interpreting the Proterozoic geology, tectonics, and mineral deposits of the Southwest. Unfortunately, his mapping was never made public, until now.
From the mid-1970s to the early 1990s, Phil traversed Arizona’s Transition Zone visiting and studying nearly every exposure of Proterozoic rocks. He described this work in his 1986 dissertation, ‘The Proterozoic tectonic evolution of Arizona’, and two subsequent papers from the Arizona Geological Society’s Digest 17, but he did not disclose his geologic maps. He issued, instead, small-scale, state-wide overviews of the distribution of Proterozoic rocks.
Phil passed away in Payson, Arizona, in Feb. 2012. In Sept. 2017, Donna Smart, Phil’s widow, donated Phil’s geologic map products and files – his life’s work – to the Arizona Geological Survey. Steve Reynolds (ASU Earth and Space Science Exploration) then organized and led a team of geoscientists in salvaging, reviewing, and selecting Anderson’s geologic maps to release as ‘The Philip Anderson Arizona Proterozoic Archive.‘
Reynolds & others (2017) contextualizing Anderson’s contribution to the Proterozoic of Arizona;
11 geologic topographic quadrangles (1:24,000) from central Arizona’s Bradshaw Mountains, with key and legend;
A suite of geologic, structural, and tectonic illustrations;
9 sub-regional geochemical plots;
2 papers (totaling 150 p.) authored by Phil Anderson and published in the Arizona Geological Society’s Digest 17.
This is the first of a suite of Anderson geologic map products that we plan to release. The remaining Anderson collection comprises dozens of other topographic maps with original geologic observations and notes regarding structures and mineralogy. It will take several hundred hours to review, process, and prepare these materials for release.
In the meantime, researchers working in the Proterozoic of Arizona’s Transition Zone are advised to reach out to the AZGS with specific requests for information.
Acknowledgments. We thank Donna Smart for preserving and donating Phil Anderson’s geologic research. We thank, too, David Briggs (President) and the Arizona Geological Society Executive Committee for their generous permission to include Phil’s two papers from AGS Digest 17.
Anderson, Phillip, 1986, The Proterozoic tectonic evolution of Arizona; Tucson, University of Arizona, unpublished PhD dissertation, 416 pages.
Anderson, Phillip, 1989a, Proterozoic plate tectonic evolution of Arizona, in Jenney, J.P., and Reynolds, S.J., 1989, Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17, p. 17 – 55.
Anderson, Phillip, 1989b, Stratigraphic framework, volcanic plutonic evolution, and vertical deformation of the Proterozoic volcanic belts of central Arizona, in Jenney, J.P., and Reynolds, S.J., 1989, Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17, p. 57 -147.
Reynolds, S.J, Conway, F.M., Johnson, J.K., Doe, M.F., Niemuth, N.J., 2017, The Phillip Anderson Arizona Proterozoic Archive. Arizona Geological Survey Contributed Report CR-17-D, 2 p.
Geoscientists agree, there is no such thing as an earthquake season. The tectonic forces producing earthquakes are inured from changes in meteorological or astronomical conditions; the latter involves fluctuation in gravitational forces due to the position of Earth’s Moon.
Arizona does, however, have an earth fissure season. A season when earth fissures are more likely to first appear or undergo renewed activity. Central and southeastern Arizona’s earth fissure season accompanies the onset of torrential rainfall of the summer monsoon, from mid-June to late September, with most precipitation occurring from mid-July to mid-August.
In southern and western Arizona, Cochise, La Paz, Maricopa, Pima and Pinal Counties all host earth fissures. In these five counties, we‘ve identified nearly 30 discrete earth fissure study areas, each with its own history, and comprising a collective 170 miles of mapped fissures and an additional 180 miles of reported but unconfirmed fissures. (Why unconfirmed? Three principal reasons: 1) ground disturbance has effectively masked the fissure; 2) built infrastructure now covers the fissure; 3) the feature was incorrectly identified as a fissure initially.)
Release of 4 revised earth fissure maps
Each monsoon season finds the AZGS’ mapping team in the field addressing new leads and revisiting fissures with a history of activity. Mapping results are compiled on existing earth fissure study area maps, which are then revised, re-versioned, and released online at the interactive Natural Hazards in Arizona site. At the same time, we release an updated ESRI spatial data file (.shp) and Google Earth KMZ file, ‘Locations of Mapped Earth Fissure Traces in Arizona’, versioned to the date of release, in this case 06 Nov. 2017.
This year we are releasing revised maps for four earth fissure study areas (Figure 1):
Two of these, Apache Junction and Chandler Heights, have largely shifted from agricultural lands to residential or industrial use lands, markedly increasing the hazard and risk that accompanies fissuring.
Fissure activity ranges widely within and between study areas. Not all fissures are created equal; and not all fissures display activity each monsoon season. Most study areas retain some active fissures that either display slow incremental expansion, or dramatic episodic growth powered by eroding sheet flow accompanying torrential rains; sheet flow fans across the valley surface as a thin sheet of water spilling into open fissures eroding sidewalls and causing gullying.
Existing fissures frequently capture numerous drainages leading to incision (headcutting) on the up-channel side. Fissures often form orthogonal to the natural drainage direction, so channels and washes intersected by the fissure deliver water during and after rains.
With reduced groundwater harvesting and waning subsidence, fissures may transition from active to inactive status. When this occurs, they become sediment traps for wind- and water-borne sediments – clays, silts and sands – that subsume the fissure, masking its diagnostic morphology – a wide open throat, steep to inclined sidewalls and a hummocky, irregular base. Reactivation of dormant, partially filled earth fissures, may occur if heavy runoff, coupled with even modest land subsidence that produces tensional forces sufficient to reopen the fissure, counters the ‘healing’ process, leading to a wider and more deeply incised fissure.
Apache Junction: Case Study of a Reactivated Fissure
The Apache Junction earth fissure study area map was first released in April 2008. Over the past several years AZGS Earth Fissure manager Joe Cook has revisited the Apache Junction virtually, via Google Earth, and physically to examine new or reactivated earth fissures. According to Cook, ‘there’s about 0.8 miles of new fissures in Apache Junction since April 2008. Many of the new fissures formed parallel to existing fissures or connected gaps in formerly discontinuous fissures.’
On the morning of July 24, 2017, following heavy rains on the late evening and early morning hours of 23-24 July, nearly 320 feet of fresh fissure opened near West Houston Ave., Apache Junction (Figure 2). This new feature is part of a larger fissure zone that stretches for more than 2 miles from near the junction of Baseline and Meridian Roads to south of West Guadalupe Road (Figure 2a). The fissure complex tunnels below streets, state trust land, private property, and large power lines.
According to Joe Cook’s report; ‘The fissure cracked West Houston Ave and an open void was visible beneath the road through a collapsed pothole. The road was closed to vehicle traffic immediately, but additional road collapse occurred over the days and weeks that followed. Large open depressions approximately 5-15 feet across and up to 8 feet deep, partially filled with collapsed material, were visible on private property to the south of Houston Ave. These open depressions were connected by parallel cracks beginning at Houston Ave to the north. Hairline cracks continued south of the southern-most depression for approximately 80 feet. Locally, a void space was visible below the hairline cracks indicating a strong potential for additional collapse.’
‘North of Houston Ave, the new fissure paralleled numerous, active and inactive, older fissures across the undeveloped desert floor. Additional reactivation and collapse along previously mapped fissures was observed beneath the powerlines in the southern part of the Apache Junction Study area.’
‘The cause for collapse of the fissure beneath Houston Ave is probably related to years of subsurface erosion along a buried earth fissure trace which intercepts rainwater from numerous drainages captured by the open portion of the fissure north of Houston Ave. During heavy rain events a substantial volume of floodwater is delivered to the fissure in a drainage ditch adjacent to the north side of W Houston Ave. Waning flow in this drainage ditch was observed to be pouring into the open fissure on the morning of July 25, 2017. No flow in the drainage ditch was observed downstream of the intersection with the earth fissure. The water draining into the fissure was not visible along the fissure anywhere else; water poured into the fissure in a free fall of about 8 feet before disappearing to unknown depths. Void space for further collapse must be substantial, which suggests that continued collapse following heavy rains is possible.’
By August 15, 2017 the collapsed portion of the fissure within the private property south of Houston Ave had been filled, presumably by the owner. But additional damage was evident, and the collapsed section of Houston Ave. remained closed.
Tator Hills: Case Study of a Fresh Fissure
Over the past several years, Tator Hills in southern Pinal County displayed the greatest fresh fissure activity of the four study areas (Figure 3). Imagery served by Google Earth shows that between Mar. 2014 and Dec. 2014, a mile-long, north-south trending earth fissure unzipped about 13 miles south of Arizona City. Sometime after March 2016, the fissure extended an additional ¾ mile to the south. The appearance of this fresh, 2-mile long fissure in an area of modest land subsidence ~ 1 inch (3 cm) annually over the past decade, and otherwise lacking active fissure formation since the early 1990s, was surprising (Cook, 2017).
Applying drone technology to fissures. In Jan. 2017, AZGS geoscientists captured a real-time synoptic view of the newest Tator Hills fissure using a DJI-PhantomTM Drone. AZGS research scientist Brian Gootee piloted the drone and captured videos at 2.7K horizontal resolution, as well as 100s of high resolution, 12 Mb static JPEG images. The latter were stitched together using AgiSoft PhotoScanTM software and analyzed using both AgiSoft PhotoScanTM and ESRI’s ArcGISTM.
At our AZGS Youtube channel, the Tator Hills fissure videos have been viewed an astounding 780,000 times! See Drone technology examining an earth fissure or Drone video of a fresh earth fissure, Tator Hills, Arizona.
The drone’s bird’s-eye view yielded a suite of derivative products – oblique orthoimagery, relief/slope map, digital elevation model (DEM), and topographic maps with contour interval of 1- to 2-feet (Figure 4) – that afford a fresh view of fissure geometry, structure, and topography that may yield new insights into the formative and evolutionary processes of fissures.
Chandler Heights and Three Sisters Buttes. Since release of earlier mapping, we documented subtle changes in some fissures at Chandler Heights (2016), Maricopa County, and Three Sisters Buttes (2012), Cochise County. Chandler Heights infamous ‘Y-Fissure’, so called because of its Y-shaped geometry, remains active but the dramatic reopening and lateral extension observed in previous years has not recurred over the past several years. Nonetheless, the ‘Y-Fissure’ remains of great interest, in part because it winds through neighborhoods in east Queen Creek.
Agriculture is the economic engine that drives Cochise County. The Three Sisters Buttes study area lies several miles southeast of Willcox Playa. Groundwater withdrawal and concurrent basin subsidence continues there unabated and from May 2010 to April 2017, maximum subsidence in the basin reached 9.8 – 15.7 in; 5 to 15 times greater than subsidence observed in the Tator Hills. In rural Cochise County, fissures chiefly threaten roads and pipelines and road signs warning of fissures is a common sight (Figure 5).
Some Observations & Final Thoughts
For the foreseeable future, earth fissures remain a geologic hazard in central and southeastern Arizona. With urban and suburban areas aggressively expanding into former agricultural areas, county and municipal planners may anticipate new and renewed incidents of costly and potentially hazardous impacts, as evinced by the recent damage to the W. Houston Rd. and nearby industrial plant in Apache Junction.
The state of earth fissures in Arizona. Nonetheless, there is hope on the horizon for a diminished threat from earth fissures. According to a recent blog post by hydrologist Brian Conway (Arizona Dept. of Water Resources), ‘Land subsidence rates within the Phoenix and Tucson Active Management Areas (AMAs) have decreased between 25% and 90% compared to the 1990s. This is a result of decreased groundwater pumping, increased groundwater recharge, and recovering groundwater levels in the two AMAs.’
Controlling groundwater pumping reduces basin subsidence, which should in turn re-establish hydrostatic equilibrium across impacted basins, thereby reducing the extensional stresses that lead to fissure formation.
Since 2007, systematic mapping of fissure study areas in Maricopa, Pima and Pinal Counties has uncovered few new earth fissures. Moreover, many fissures mapped between 2007 and 2009 showed physical evidence of having formed years or decades before. It could well be that the rate of earth fissure formation in most study areas reached its apex in the latter quarter of the 20th century. If so, land managers in these impacted areas should anticipate seeing fewer new fissures forming and, perhaps, waning reactivation of existing fissures.
In Cochise County, where groundwater pumping and basin subsidence continues unabated, we anticipate new fissures forming annually and existing fissures reopening.
Note of caution. There could be a substantial time-lag between reduced pumping, waning subsidence rates, and the end of new or renewed fissuring. By way of example, subsidence in the Tator Hills area has slowed substantially since the latter quarter of the 20th century. From 2004 to 2017, total subsidence proximal to the 2-mile long fissure was between 1.6 to 3.2 inches; a magnitude of subsidence that seems inconsistent with the formation of a 2-mile long fissure. This fissure may have formed years before, only to break the ground surface in 2014. This could be true of concealed fissures in other study areas, too. We strongly recommend that civil authorities, farmers, contractors, and the public remain on the alert for the sudden emergence of rogue, outlier fissures.
Final Thoughts. The AZGS fissure mapping team continues to monitor earth fissure study areas, both virtually, via Google Earth and fresh National Agriculture Imagery Program (NAIP) imagery, and physically by returning to study areas. We confer regularly with county and municipal authorities regarding reports of reactivated or new fissures. Last, we remain aware of the potential of fissures forming in areas where the imbalance between groundwater harvesting and recharge leads to measurable basin subsidence, such as in agricultural lands of Cochise County and the McMullen Valley of Maricopa and La Paz Counties.
Arizona Land Subsidence Group, 2007, Land Subsidence and Earth Fissures in Arizona: Research and Informational Needs for Effective Management: Arizona Geological Survey Contributed Report CR-07-C, 29 p.
Schumann, H.H., and Cripe, L.S. (1986). Land subsidence and earth fissures caused by groundwater depletion in Southern Arizona, U.S.A. In A.I. Johnson, L. Carbognin & L. Ubertini (Eds.], Proceedings of the 3rd International Symposium on Land Subsidence, Venice, Italy, 19-25 March 1984 (pp. 841-851). International Association of Hydrological Sciences, Publication 151.