In FY 2019, there were 380 active, full-time mines or development projects in the state of Arizona. Arizona typically ranks 2nd to Nevada in non-fuel mineral production annually in the U.S. mining industry. Mined mineral resources in Arizona (Fig. 1) range from metals, chiefly copper with minor production of gold, silver, iron ore, lead and zinc (Fig. 2), to a broad suite of industrial minerals dominated by aggregate (sand, gravel, and building stones) complemented by cement and lime, flagstone, gemstone, cinders, and gypsum, among other mineral resources.
The report contains a state map showing mine locations and plates of Arizona counties which show the distribution of active mines with respect to legislative districts and major road systems.
Congressman Raul Grijalva is at it again with his proposed H.R. 2579 Hardrock Leasing and Reclamation Act of 2019 which would probably make future mining in America uneconomic. Among other things, the law would impose a 12.5% royalty on productions and eliminate valid mining claims after 20 years (read full text). The royalty is extremely punitive to an industry that already pays over 45 percent of its earnings to federal, state and local governments, in the form of taxes, fees, royalties and other assessments. Currently, the U.S. is 100% import-reliant for 18 minerals – 14 of which have been deemed “critical” by the departments of defense or interior.
The American Exploration & Mining Association (AEMA) notes that:
The sweeping changes in Rep. Grijalva’s legislation are unnecessary and a disaster in the making for the domestic mining industry and for America.
The fact is, hardrock mining is fundamentally different than oil, gas, and coal because it is much more difficult to find and develop hardrock mineral resources. This bill ignores these differences and seeks to force-fit royalty and leasing programs for coal, oil, and gas on hardrock mining. Without question, the Grijalva bill, if enacted, would substantially chill private-sector investment in exploring for and developing minerals on federal land and dramatically increase our already extensive reliance on foreign sources of minerals.
This bill poses a significant threat to our Nation’s economic security and to our defense, technology, manufacturing, infrastructure, and renewable energy sectors, all of which rely on minerals from mining. The country will suffer as high paying family-wage jobs are exported, and our rural communities will experience disproportionately severe economic hardships.
Geologist Ned Mamula (adjunct scholar in Geosciences at the Center for the Study of Science, Cato Institute) opines that:
Mining is a long-term investment process and, although two decades is a long time, some hardrock mines now take 10 years or more just to get approved. What company would be willing to invest hundreds of millions of dollars in a new mine only to see its mining claims suddenly revoked?
Remarkably, the timing of this “reform” is just as bad as the substance. U.S. demand for minerals is climbing steadily: for hundreds of defense, aerospace, electronic, energy, medical, computing, transportation and other applications. Yet, our dependence on China for minerals is at an all-time high and growing, despite increasingly tense diplomatic relations.(Read full article)
Matthew Kandrach, President of Consumer Action for a Strong Economy notes:
The taboo against hard-rock mining in the United States is nonsensical and should be abandoned. Instead, America should embrace a far wiser policy of ensuring greater access to minerals on our public lands, since it’s in our national and economic interest. This would help reduce our heavy dependence on foreign nations for minerals that are needed in the production of advanced weapons systems and a multitude of consumer technologies.
The current problem stems from America adhering to a highly duplicative and inefficient system of regulatory permits and oversight that governs domestic mining. Over all, the mining industry is struggling with a regulatory system that forces them to wait seven to 10 years to obtain a mining permit, in contrast to Canada and Australia where the process takes two to three years.
The permit system was set up during a very different era when the U.S. dominated the production and use of minerals. But those days are long past. China is now the world’s leading producer and exporter of minerals and metals, supplying many that are critical to U.S. manufacturing, our technology and energy sectors, and national defense. Our ongoing dependence is not only a potential vulnerability during a time of increased global tensions, but greatly limits our nation’s ability to capitalize on our mineral wealth. (Read more)
In March, 2019, President Trump signed legislation creating the 3,600 square mile Santa Cruz Valley National Heritage Area in parts of Pima and Santa Cruz Counties, Arizona. This has long been a pet project of Congressman Raul Grijalva. The proposed boundaries of the heritage area encompass major copper mines, sources of construction aggregate, and many ranches.
According to the Arizona Geological Survey, the mines in the area have produced 65 percent of the nation’s copper. (Maps in this article are from AZGS.) It remains to be seen whether establishment of an NHA will impact mining and mineral exploration.
The heritage area will be managed through the National Park Service which will contract management to a “local coordinating entity” which in this case is the Santa Cruz Valley Heritage Alliance. The Alliance will receive $1 million per year up to a maximum of $15 million for its services.
According to the House version of the legislation (link 3 below):
The purposes of this Act include:
(1) to establish the Santa Cruz Valley National Heritage Area in the State of Arizona;
(2) to implement the recommendations of the Alternative Concepts for Commemorating Spanish Colonization study completed by the National Park Service in 1991, and the Feasibility Study for the Santa Cruz Valley National Heritage Area prepared by the Center for Desert Archaeology in July 2005;
(3) to provide a management framework to foster a close working relationship with all levels of government, the private sector, and the local communities in the region and to conserve the region’s heritage while continuing to pursue compatible economic opportunities;
(4) to assist communities, organizations, and citizens in the State of Arizona in identifying, preserving, interpreting, and developing the historical, cultural, scenic, and natural resources of the region for the educational and inspirational benefit of current and future generations; and
(5) to provide appropriate linkages between units of the National Park System and communities, governments, and organizations within the National Heritage Area.
The Act also gives these reassurances:
Nothing in this Act:
(1) abridges the rights of any property owner (whether public or private), including the right to refrain from participating in any plan, project, program, or activity conducted within the National Heritage Area;
(2) requires any property owner to permit public access (including access by Federal, State, Tribal, or local agencies) to the property of the property owner, or to modify public access or use of property of the property owner under any other Federal, State, Tribal, or local law;
(3) alters any duly adopted land use regulation, approved land use plan, or other regulatory authority of any Federal, State, Tribal, or local agency, or conveys any land use or other regulatory authority to any local coordinating entity, including but not necessarily limited to development and management of energy, water, or water-related infrastructure;
(4) authorizes or implies the reservation or appropriation of water or water rights;
(5) diminishes the authority of the State to manage fish and wildlife, including the regulation of fishing and hunting within the National Heritage Area; or
(6) creates any liability, or affects any liability under any other law, of any private property owner with respect to any person injured on the private property.
That sounds good in theory, but experience with other National Heritage Areas is not so good.
The Heritage Foundation (link 5 below) opines:
There are three key reasons why Congress should not create any new NHAs and why existing NHAs should become financially independent of the federal government, as their enabling legislation requires.
1) NHAs divert NPS resources from core responsibilities. NPS advocates and staff have long complained about the limited resources that Congress provides in comparison to its extensive responsibilities. Both the Government Accountability Office (GAO) and the Congressional Research Service estimate that the cost of NPS’s maintenance back-log exceeds several billion dollars and is rising despite increased annual appropriations.
2) Federal costs for NHAs are increasing at a rapid rate.
3) NHAs threaten private property rights. On the surface, most of the legislation designating an NHA, and the subsequent management plans that guide them, include explicit provisions prohibiting the NPS or the management entity from using eminent domain to acquire property. They also prohibit the use of federal funds to acquire private property by way of a voluntary transaction with a willing seller.
Nonetheless, NHAs pose a threat to private property rights through the exercise of restrictive zoning that may severely limit the extent to which property owners can develop or use their property. Termed “regulatory takings,” such zoning abuses are the most common form of property rights abuse today. They are also the most pernicious because they do not require any compensation to owners whose property values are reduced by the new zoning. (Read full article for details.)
The American Policy Center (link 4 below) opines:
Specifically, what is a National Heritage Area? To put it bluntly, it is a pork barrel earmark that harms property rights and local governance. Let me explain why that is. Heritage Areas have boundaries. These are very definite boundaries, and they have very definite consequences for folks who reside within them. National historic significance, obviously, is a very arbitrary term; so anyone’s property can end up falling under those guidelines.
The managing entity sets up non-elected boards, councils and regional governments to oversee policy inside the Heritage Area.
In the mix of special interest groups you’re going to find all of the usual suspects: Environmental groups; planning groups; historic preservation groups; all with their own private agendas – all working behind the scenes, creating policy, hovering over the members of the non-elected boards (perhaps even assuring their own people make up the boards), and all collecting the Park Service funds to pressure local governments to install their agenda. In many cases, these groups actually form a compact with the Interior Department to determine the guidelines that make up the land use management plan and the boundaries of the Heritage Area itself.
Now, after the boundaries are drawn and after the management plan has been approved by the Park Service, the management entity and its special interest groups, are given the federal funds, typically a million dollars a year, or more, and told to spend that money getting the management plan enacted at the local level.
Here’s how they operate with those funds. They go to local boards and local legislators and they say, Congress just passed this Heritage Area. “You are within the boundaries. We have identified these properties as those we deem significant. We have identified these businesses that we deem insignificant and a harm to these properties and a harm to the Heritage Area. We don’t have the power to make laws but you do. And here is some federal money. Now use whatever tools, whatever laws, whatever regulatory procedures you already have to make this management plan come into fruition.”
This sweeping mandate ensures that virtually every square inch of land within the boundaries is subject to the scrutiny of Park Service bureaucrats and their managing partners. That is the way it works. It’s done behind the scenes – out of the way of public input.
True private property ownership lies in one’s ability to do with his property as he wishes. Zoning and land-use policies are local decisions that have traditionally been the purview of locally elected officials who are directly accountable to the citizens that they represent.
But National Heritage Areas corrupt this inherently local process by adding federal dollars, federal mandates, and federal oversight to the mix. Along with an army of special interest carpet baggers who call themselves Stake Holders. (See the article for much more.)
1) P.A. Pearthree and F.M. Conway, 2019, Preliminary evaluation of mineral resources
of the Santa Cruz Valley National Heritage Area, Arizona, Arizona Geological Survey, Open-file Report OFR-19-03 (link)
2) Southwestern Minerals Exploration Association (SMEA), 2001, Mineral Potential of Eastern Pima County, Arizona, Arizona Geological Survey Contributed Report 01-B (link) (Note: I am one of the co-authors of this report.)
3) Text of House version of establishing legislation: H.R. 6522 (115th): Santa Cruz Valley National Heritage Area Act (link)
4) Tom DeWeese, American Policy Center, 2012, National Heritage Areas: the Land Grabs Continue (link)
5) Cheryl Chumley and Ronald Utt, 2007, National Heritage Areas: Costly Economic Development Schemes that Threaten Property Rights, The Heritage Foundation (link)
The Arizona Geological Survey has just published a geological evaluation on the new Santa Cruz Valley Natural Heritage area in southern Arizona. Here is the introduction from AZGS:
The newly designated Santa Cruz Valley National Heritage Area includes ~ 3,600 square miles (9,378 square kilometers; 2,304,000 acres) and hundreds of mines distributed in 20 mining districts in Pima and Santa Cruz Counties. AZGS just released a preliminary evaluation of metallic and industrial minerals of America’s newest National Heritage Area.
The report is accompanied by six figures, two tables and citations for more than 50 published geologic reports and maps from the AZGS and the US Geological Survey. All of which are available as free PDF downloads.
Citation: Pearthree, P.A. and Conway, F.M., 2019, Preliminary evaluation of mineral resources of the proposed Santa Cruz Valley National Heritage Area, Arizona. Arizona Geological Survey Open-File Report OFR-18-03<http://repository.azgs.az.gov/uri_gin/azgs/dlio/1911>;, 7 p.
My comment: It is yet to be determined if designation of a heritage area will have any detrimental effects on mining and mineral exploration. Mining has long been a part of the heritage of this area.
The US Geological Survey (USGS) has updated its assessment of volcanic hazard threats in the United States. Most volcanoes occur along the Pacific coast of the U.S., within the Aleutian Islands of Alaska, and on certain other Pacific islands such as Hawaii. The USGS lists 161 volcanos as dangerous, of which, 18 are considered to have a “very high” threat for damage.
Kilauea volcano in Hawaii, which erupted last year, ranks number 1 as the most hazardous volcano. Mount St. Helens in Washington comes in at number 2. It last erupted in 1980.
Yellowstone caldera in Wyoming comes in at 21, a “high” threat. The San Francisco Volcanic Field near Flagstaff, AZ comes in at 80, a “moderate” threat.
According to the USGS:
The United States is one of Earth’s most volcanically active countries, having within its territory more than 10 percent of the known active and potentially active volcanoes. The geographic footprint of U.S. volcanoes is large, extending from arctic Alaska in the north to tropical American Samoa south of the Equator, and from Colorado in the east to the Commonwealth of the Northern Mariana Islands in the western Pacific. Since 1980, there have been 120 eruptions and 52 episodes of notable volcanic unrest (increased seismicity, observed ground deformation, and (or) gas emission) at 44 U.S. volcanoes.
Volcanoes produce many kinds of destructive phenomena. In the United States over the past 38 years, communities have been overrun by lava flows in Hawaii and in Washington State, a powerful explosion has devastated huge tracts of forest and killed people tens of miles from the volcanic source, and debris avalanches and mudflows have choked major river ways, destroyed bridges, and swept people to their deaths. In California, noxious gas emissions have resulted in fatalities, and in Hawaii, given rise to widespread respiratory ailments. Airborne ash clouds have caused hundreds of millions of dollars of damage to aircraft and nearly brought down passenger jets in flight in U.S. and international airspace, and ash falls have caused agricultural losses and disrupted the lives and businesses of hundreds of thousands of people in Washington State and Alaska. The growing risk of such severe threats to communities, property, and infrastructure downstream and downwind of volcanoes drives the need to decipher past eruptive behavior, monitor the current activity, and mitigate damaging effects of these forces of nature.
When one thinks of earthquakes in the U.S., we often think of the west coast. But, on a U.S. earthquake hazards map, there is a big bull’s eye in the Midwest along the Mississippi River, centered on the town of New Madrid, Missouri. According to the U.S. Geological Survey (USGS) this area, the New Madrid seismic zone has “ repeatedly produced sequences of major earthquakes, including several of magnitude 7 to 8, over the past 4,500 years.”
The most famous New Madrid earthquakes occurred from December 16, 1811, through February 7, 1812. The three main earthquakes measured 7.3-7.5 on the Richter scale. Aftershocks persisted through 1813.
According to the USGS:
1811, December 16, 08:15 UTC Northeast Arkansas – the first main shock
2:15 am local time
This powerful earthquake was felt widely over the entire eastern United States. People were awakened by the shaking in New York City, Washington, D.C., and Charleston, South Carolina. Perceptible ground shaking was in the range of one to three minutes depending upon the observers location. The ground motions were described as most alarming and frightening in places like Nashville, Tennessee, and Louisville, Kentucky. Reports also describe houses and other structures being severely shaken with many chimneys knocked down. In the epicentral area the ground surface was described as in great convulsion with sand and water ejected tens of feet into the air liquefaction).
During the February 7 earthquake, “Large waves (seiches) were generated on the Mississippi River by seismically-induced ground motions deforming the riverbed. Local uplifts of the ground and water waves moving upstream gave the illusion that the river was flowing upstream. Ponds of water also were agitated noticeably.”
The New Madrid seismic zone is underlain by the Reelfoot Rift, a large fault zone with mainly horizontal movement. It is speculated that this rift was formed about 750 million years ago during the breakup of the supercontinent Rodinia. The Reelfoot Rift failed to split the continent, but remains a weak area in Earth’s crust. From time to time, pressure from the movement of tectonic plates causes movement on this weak area resulting in earthquakes.
The USGS “concludes that the New Madrid Seismic zone is at significant risk for damaging earthquakes that must be accounted for in urban planning and development. A fundamental problem is the lack of knowledge concerning the physical processes that govern earthquake recurrence in the Central US, and whether large earthquakes will continue to occur at the same intervals as the previous three clusters of events. ”
To read more, including eyewitness accounts, and a summary of 1811-1812 New Madrid earthquakes sequence, go to:
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
UPDATE 2: New Study, July 5, 2019:
From: University of Auckland
Pacific atolls can adapt to rising seas and extreme storms – new study
Low-lying Pacific islands in atoll archipelagos such as Tuvalu, Tokelau and Kiribati are likely to adapt to the effects of climate change rather than simply sink beneath the waves, a new study shows. Read more