Environmental Consequences of Open Pit Mining

An open pit mine is a type of excavation where surface and subsurface materials (soil and rock) are removed, typically through use of explosives and mechanical mining and hauling equipment, to gain access to commercially valuable ores or other buried natural resources, including coal and gemstones, that are relatively close to the surface. The mined material may be defused throughout the rock, contained in veins, or concentrated in layers. The pit (also known as borrow) is “open” to the atmosphere for as long as the mine continues in operation. Waste overburden may be piled in a dump at the surface, near the edge of the open pit, or deposited in adjacent valleys. Processed rock from which the ore has been removed is known as tailings and is normally pumped as a slurry to a nearby tailings or settling pond, where the water eventually evaporates, leaving behind hazardous materials. 

Author’s Note: A quarry is an open-pit mine that produces building materials and dimension stone, such as granite, quartzite, marble, slate, bluestone, limestone, or sandstone, etc.

Historically, the far greater majority of open pit mines have been constructed as an exercise in economics constrained by geologic and mining engineering principles with little or no consideration given to the environment in which the mining occurs. Even today, many American mining operations pay little more than lip service to environmental protection or restoration or mitigation.

By its very nature, open pit mining (also known as strip mining and opencast mining) is environmentally destructive. Surface mining operations, especially those that are large-scale, always alter and disturb the Earth’s surface, even if what are usually euphemistically known as “effective” mitigation measures are applied and the site is restored to a condition said to “approach” or “resemble” its natural state. That disturbance, in turn, has numerous direct, indirect, short- and long-term potentially adverse effects on the landscape and on nearby human communities, including the following and other factors too numerous to detail in this modest definition. Readers who desire a more detailed examination of the adverse effects of mining in general should consult three previous posts on this blog on the effects of underground mining (see posts on March 5, 6, and 7).

Topographic modifications: including the large-scale removal of soil, vegetation, and overburden to access ore or other mineral deposits and create nearby sites for tailings storage, water storage dams and reservoirs, berms, and waste disposal pits. Those alterations can be caused by the construction of exploration or access roads and mining-smelting infrastructure—such as cranes, hoists, conveyor systems, buildings, electrical substations and distribution lines, power generating equipment and facilities, workshops, showers and decontamination facilities, testing labs, wastewater treatment facilities, offices, parking-vehicle storage areas, material storage, and smelters, etc.—the use of mechanized equipment such as off-road vehicles, drill rigs, or seismic exploration vehicles and construction-operation of mining activities in previously remote, roadless, mountainous regions, high latitudes, or wetlands where human activity had resulted in little alteration of relatively pristine ecosystems. Perhaps the most egregious and horrific example of topographic modifications in strip mining is the mountaintop removal/valley filling coal mining process currently ongoing in parts of Appalachia that leaves behind a brutally scarred, environmentally sterile moonscape that destroys human settlement patterns as well as habitats and ecosystems.


Author’s Note: A common topographic alteration to the landscape in open pit mines is an engineered dam/dyke system known as a tailing pond/pit, which is used to store mining refuse/gangue produced by the separation of economically valuable materials from the uneconomic part of an ore. In a great many instances, the containment structures comprising these ponds are not meant to be permanent and may be constructed of compacted earth, forming what are embankment dams. In areas of seasonally high rainfall, those structures may experience greater volumes of water than was anticipated and fail, often catastrophically, flooding areas downstream with a slurry of mud-like materials and water, resulting in loss of life and property. Here's an example. The Mount Polley open pit copper/gold mine, covering 18,892 hectares or nearly 46,700 acres in south-central British Columbia is operated by Vancouver-based Imperial Metals. The mill processes 20,000 tons of rock per day. In early August, 2014, a tailings pond dam at the mine failed, releasing at least 10 million cubic meters of contaminated water and waste rock into a local creek, expanding its width from four feet to 150 feet before entering nearby Quesnel Lake and its connected waterways, which are important habitats for Chinook and Sockeye Salmon as well as Rainbow Trout and White Sturgeon. The pond contained tailings from the mining process and were contaminated with arsenic, cadmium, copper, lead, and mercury, among other toxins and heavy metals that are hazardous to life. Another very recent example is the Samarco iron ore mine in Minas Gerais, Brazil, a joint venture between the Anglo-Australian mining giant, BHP Billiton, and Brazil’s biggest iron ore miner, Vale SA, which failed in early November 2015, releasing 81 million cubic yards of mining waste, killing perhaps 20 people, destroying nearby villages housing more than 600 people, polluting drinking water over an enormous area, and adversely affecting the Rio Doce, which is one of Brazil's most important rivers, and the adjacent landscape for more than 300 miles downstream. Not to mention the issue that mining companies love to gloss over in their press releases meant to reassure the affected public: residues from the iron mining operations and the consequent flooding are toxic and may be very hazardous to human and animal health. According to Brazil’s environmental agency, IBAMA, 50 million metric tons of toxic sludge from the mine dam failure are, at the end of December 2015, spreading along 30 miles of coastal beaches between the states of Rio de Janeiro and Bahia, turning the pristine blue waters brown and sliming the beaches themselves. When tailings impoundments are abandoned, improperly remediated, and gradually dry up, the resulting dust, which can and often does consist of toxic materials rather than simple mud/dirt particulates, can cover the adjacent environment and nearby settlements, increasing risks to life and health, including respiratory, skin, gastrointestinal (from inadvertent ingestion) and other adverse effects that can include different types of cancer.

Soils: changes in characteristics through accelerated wind and water erosion, sharply increased acidity and salt content, development of nutrient deficiencies or imbalances, compaction, surface crustiness, or desiccation. Soils can be removed partially or entirely, altered, indurated, contaminated with toxins, or otherwise adversely affected by road building or mining construction to certain depths below the surface such that short-term and even mid-term recovery following reclamation is problematic. The fairly intense disturbance of soil surfaces by mining activities may make soils susceptible to water and wind erosion, thus contributing to sediment loading in local or regional stream systems that reduce water quality and aquatic habitat. Chemical particulates and metals from smelter emissions and airborne tailings can settle on soil surfaces near or some distance from mineral processing facilities, although typically contamination of soils decreases with distance from the contaminant source. In many cases, toxic substances have been deposited along roads leading from the mine and have adversely affected not only soils in residential areas but also the health of people and animals living in proximity to the roads.

Surface water: changes in quality (especially in terms of drinking water and such uses as agriculture and other water-intensive industrial/commercial operations), discharge quantities such as stream flow regime fluctuations with sharper flow peaks and reduced dry season flows, stream channel alterations from erosion and slumping, and runoff including wash-off or hazardous chemical leachates (such as sulfates, sulfides, and salts) from unrehabilitated and poorly revegetated mine dumps and discard areas and the interrelated problems involving the release of heavy metals (including lead, copper, mercury, aluminium, selenium, zinc, uranium, nickel, chromium, and others) and acids from tailing piles, especially sulfuric, into nearby water bodies where excess acid generation overwhelms the natural buffering capabilities present in adjacent land and water resources. In the 1990s, the U.S. Forest Service estimated that between 20,000 to 50,000 mines on federal lands were generating toxic acid discharges that adversely effected between 5,000 to 10,000 miles of streams. 

Author’s Note: Another point to consider in the above materials about the nature of leachates is the following example: fresh water that is poured over ground coffee beans leaches far more essence of coffee than if the same water percolated over whole coffee beans since more surface area is exposed to the chemical effect. So it is with mine tailings versus intact igneous rock structures. That specific environmental problem is extremely important and complex since different metal species have different bio-availabilities and some of those species are much more toxic and hazardous than others. Speciation (the term of interest used above is metal species) is the proportion of the metal in different forms, such as ions, ion pairs and combinations, complex molecules, colloids, and precipitates. Incidentally, if you do not believe that acid mine drainage is an extraordinarily serious real world problem with working and abandoned mines, you should wake up and read about the horrific Animas River spill in Colorado (USA) in early August 2015 that released three million gallons of lead, arsenic, cadmium, and other highly toxic chemicals into the stream from the abandoned Gold King mine, closed one hundred years ago, that had never been properly remediated. As of mid-2016, the Gold King Mine continues to discharge acid mine drainage at a rate of about 600 gallons per minute. The really depressing news is that abandoned mine is just one of hundreds of thousands like it in the American West, at least 20,000 in Colorado alone, most of which are environmental disasters waiting to happen. All because the General Mining Law of 1872, which is still the governing legislation, did not and does not require mining companies to clean up their messes and instead allows them to turn their backs on the problem and simply walk away with their profits intact. For more information on that law and its effects on American mining, especially on gold mining, see my blog post of 4-2-12.

Groundwater: adverse effects on quality and quantity especially with regard to dewatering activities, drawdown, and techniques used to control dust and other particulates as well as acid mine drainage that infiltrates the groundwater system and adversely affects the natural pH levels, causing cascading effects on flora and fauna when the groundwater and surface water systems interact. This topic is far more complex and critical than can be described in a few short paragraphs. Serious students of the topic must investigate the various sub-topics independently.

Air quality through discharge from nearby refinery smelter stacks: pollutants include a variety of particulates (especially dust derived from many stages in the mining operation), gases that contribute to acid rain, metal vapors, noxious odors, etc., including lead and copper toxicity affecting livestock, wildlife, and human populations from air-borne particulates. Air quality issues generated by mining-milling-smelting operations not only include emissions of particulates but also fugitive dust, odors, and sulfuric acid that can produce extensive regional air pollution through sulfuric deposition and acidification of streams and lakes that in turn can cause adverse changes in aquatic biotic composition and chemical processes. Those adverse atmospheric effects can be felt many hundreds of miles from the mining source in rural areas, cities, and even other countries.

Other Air Quality Issues: Extracting metals and other ores, whether in open-pit or underground mines, using modern industrial processing typically results in large surface mounds of commercially worthless or waste rock, variously known as tailings, gangue (pronounced "gang"), or chat. At many mine sites, millions of tons of waste rock remain, the fines/dust of many of those mines are subject to airborne dispersal onto adjacent properties and steams as well as into geographically removed areas. Those airborne materials can contain heavy metals and other toxic/hazardous chemicals that can be inhaled and ingested by the residents/visitors, causing various health-related problems including lung and other diseases. Those hazardous materials can be especially deleterious to small children under six years of age who are at high risk owing to stage of physiological development.

Chemical residues: especially those from acids, hazardous and toxic chemicals, explosives, and radionuclides. Tailings ponds may frequently be toxic due to the presence of unextracted sulfide minerals and acids in the tailings or gangue (commercially valueless material in which ore is found). Those hazardous residues may wind up contaminating surface streams or groundwater or both.

Noise and vibration associated with mining activities: including the use of explosives, operation of enormous trucks and other heavy mechanical-electrical equipment, and various milling-smelting operations adversely affect nearby settlements as well as areas under human use such as parks, churches, schools, streams used for fishing and recreation, and lands used for hunting. Since most people have never experienced large-scale industrial noise and vibration it is difficult to adequately portray the critical disruptive effects they have on all human activities, including speech, sleep, thought itself, concentration, and mental health.

Flora and fauna: indigenous species are adversely affected by alterations to and loss of native habitats, vegetation cover, invasion by alien plant/animal species, altered plant community species composition, contamination and destruction of entire food webs. Disturbances of natural, quasi-natural, or cultural landscapes inevitably result in changes in composition and structure of plant species, disrupt soil strata, and stimulate invasion by disturbed-site plant species that in turn can alter composition of local invertebrate and other associated species and habitat. Those disturbances may be associated with development of roads or use of off-road vehicles during exploration and development activities. Emissions from various onsite mineral processing facilities may also act to fumigate plant communities adjacent to  through releases of toxic materials, such as sulfur dioxide (SO2), which is often lethal to foliage and consequently to the plant itself. Increasing distance from the pollution source generally results in the plant community composition gradually returning to pre-disturbance characteristics. However, long-term particulate and smelter emissions have historically adversely affected surrounding ecosystems, habitats, plant/animal biodiversity, and soils.In many cases, surface disturbance is so significant and persistent, the consequent loss of predator and other animal species can alter the local and regional ecology for many decades, even centuries.

Author's Note: The Berkeley Pit in Butte, Montana, is an inactive open pit copper mine owned and managed by Atlantic Richfield and Montana Resources. The Pit is one mile long by half a mile wide with an approximate depth of 1,780 feet holding about 45 billion gallons of water that is highly acidic (sulfuric acid) and is contaminated by high concentrations of dissolved toxic heavy metals. The Berkeley Pit was designated as a federal Superfund site in 1983. This mine popped into the news in late November 2016 when several thousand migrating snow geese died when they landed in the Berkeley Pit’s toxic water. For more information on the Berkeley Pit, see: http://www.pitwatch.org/berkeley-pit-history/

Land Subsidence after strip mine rehabilitation. Subsidence can occur after an open pit mine has been reclaimed due to changes in underground water supply, differential settling, and subsurface mechanical erosion that forms cavities or pipes that may collapse, causing the land surface to subside.

Cultural factors, including:

Aesthetic, noise, and visual effects. Although many supporters of open pit mining play down this type of adverse effect, imagine the stress caused by living with nearly constant noise and vibration from mining activities. And if the mine is located in an area that was previously forested, the visual effects, meaning the loss of vegetation and the implementation of an industrial landscape, can be significant. Loss of a landscape that has meaning for people as a result of open pit mining and the resulting environmental degradation causes mental anguish and suffering that is largely or even entirely discounted or denied by mine operators but is nevertheless real.

Land use modifications including reduced agricultural or grazing capacity; introduction of non-native species as part of re-planting plans; increased infrastructure, including power, water, and gas corridors; transport and service corridors (railway lines, roads, pipelines, conveyors, airstrips, port facilities); social infrastructure costs, including rapidly increased demand for mining-related housing, commercial-retail services, food and entertainment, education, social services, emergency services, medical services, etc.; loss of natural and semi-natural streams and associated valleys when those areas are buried by overburden and turned into wastelands; loss of residential uses and communities in valleys buried by overburden; and addition of new surface uses and facilities (e.g. offices, laboratories, workshops, vehicle parking, repair/service areas, fuel storage and dispensing depots, and warehouses, etc.). A land use cost seldom anticipated or adequately planned for is what happens to built socioeconomic uses-infrastructure (residences, schools, commercial-retail, roads, water and sewage facilities, etc.) after the mine is depleted and abandoned and the workers depart for places unknown.

Economic Costs: including short-, mid-, and long-term costs to the general public (meaning through actions of state and federal governments) of clean-up not paid for by the mining firm or the bond, which is an all too common occurrence, especially in the American Southwest. Those costs can be both significant and long-term.

The set of environmental consequences that any specific open pit mining operation will have on the natural and cultural environments depends on a number of factors: type of rock and ore being mined, scale and longevity of mining operations, efficiency and effectiveness of environmental management systems and mitigation measures that are employed by mine management, the nature and level of enforcement of government environmental regulations, and the sensitivity of the receiving environment (especially the abundance/scarcity of both surface and ground waters). Although a number of analytic methods have been proposed to measure the adverse environmental effects of surface mining, most of those techniques compartmentalize adverse effects and seldom treat those adverse effects as inextricably interrelated or systemic (for example, see Folchi, Roberto. 2003. "Environmental impact statement for mining with explosives: A quantitative method." I.S.E.E. 29th Annual Conference on Explosives and Blasting Technique. Nashville, Tennessee). Consequently, little attention is often paid to the importance of habitats, plant and animal biodiversity, watersheds, etc. as the adverse effects are reduced to quantitative scores that can be interpreted and manipulated in various ways that can justify mining operations.

Real World Examples: A mind-numbing example of the horrific multiple adverse effects on biogeophysical and human systems is Arch Coal’s Hobet 21 mountaintop removal coal mine in Lincoln County, West Virginia, where hundreds of millions of tons of former mountain top wastes have been dumped into a nearby miles-long valley with horrific adverse environmental effects.[1] For those few readers who may not be familiar with the process, mountaintop removal is a form of open pit coal mining that uses heavy explosives to remove hundreds of vertical feet of mountainous terrain to access coal seams at varying depths beneath the surface. That “overburden,” meaning millions of tons of rock fragments, is then dumped directly into adjacent valleys, destroying existing habitat, burying streams, wetlands, and forests, and causing mud and debris slides, dislodged boulders, flash floods, and the deposition of heavy metals, carcinogens, and other toxic-hazardous materials in streams and lakes.

According to the Mountain Justice website, “Mountaintop removal/valley fill coal mining (MTR) has been called strip mining on steroids.” The process is one of leveling rugged mountainous topography and leaving behind a sterile moonscape. In the past several decades, mountaintop removal mining has transformed some of the most biologically diverse temperate forests in the world in West Virginia, Kentucky, and Ohio into enormous, biologically barren open wounds on the landscape. Many sources estimate that over 500 mountains have been leveled, and many thousands of miles of Appalachian streams have been buried and polluted by that mining process. In the State of Kentucky, almost 4,000 miles of streams have been polluted, physically degraded, or destroyed by mountaintop mining.

Open pit/open cast miining techniques are also frequently used to produce precious and semi-precious metals, especially, copper, silver, and gold, in developed as well as developing nations. Examples include the Bingham Canyon Copper Mine (also known as the Kennecott Mine) southwest of Salt Lake City, Utah; Chile’s Chuquicamata Mine, the world’s largest open pit copper mine and the second deepest open-pit mine; and the Grasberg Mine in the province of Papua in Indonesia, the world’s largest gold mine and the second largest copper mine; according to the non-profit Earthworks, that mining operation dumps about 80 million tons of mining debris into the Ajkwa River system every year.

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[1] For a book full of ugly examples of how mining can kill a mountain ecosystem and the surrounding valleys, see: Erik Reece, Lost Mountain: A Year in the Vanishing Wilderness. New York: Riverhead Books/Penguin Group, 2006.

Great Pacific Garbage Patch and Gyres

The Great Pacific Garbage Patch is an almost formless collection of floating junk yards that stretch for hundreds of miles across the North Pacific Ocean. It's a genuine nightmare, a global problem made of plastic and other materials that are made, used, and carelessly discarded by humans and wind up as an enormous conglomeration of marine debris, often inside animals' stomachs or around their necks. Because the garbage patch is not one continuous floating mass, its size is difficult to determine with any degree of accuracy, though it could easily be twice as large as Texas. Typically, the Great Garbage Patch is discussed as having two major parts, the Eastern and Western.

It should be noted at the outset that the name, Great Pacific Garbage Patch, is not only a misnomer but a highly misleading misnomer. No continuous or semi-continuous island of trash has formed in the Pacific. Nor is the Garbage Patch a blanket of trash that can be seen with satellite imagery or aerial photographs. Nor does the marine debris typically consist of easily visible items such as plastic bottles, bags, and other litter. Small pieces of plastic are the most typical floating debris found in the Garbage Patch and most are so small they are not easily seen by the naked eye, not even from a nearby boat.

Modern society loves plastics because they’re cheap, lightweight, and seem to last forever. And that’s the problem; most plastics don’t biodegrade very easily, even in harsh conditions or even after being immersed in salt water and exposed to sunlight for six or seven decades. Individual pieces may become smaller, but that doesn’t diminish the problem, which is that those pieces are being consumed by an enormous variety of ocean organisms.

But not only are the plastics themselves the source of myriad health problems for ocean life-forms, they also are chemical sponges, soaking up lethal cocktails of PCBs, DDT, and nonylphenols (common family of biodegradation products of a widely distributed group of nonionic surfactants used in foods and drinks, pharmaceuticals, and skin-care products), all of which are oily toxins that do not dissolve in seawater. Plastics floating in the Eastern Garbage Patch have been found to contain up to one million times the level of those toxins that are floating in the water itself. When that plastic is indigested, the poisons are released, affecting the consuming animal, its progeny, and its predators. The toxins act as hormone disruptors that change reproduction rates, sex ratios, and disrupt the growth and function of male and female reproductive organs.

On a physical level, many types of ocean birds have been found to have consumed such large quantities of plastic that food digestion is disrupted and the animal dies of starvation or other related gastric disorders. Dutch scientists have used northern fulmars to monitor flotsam in the North Sea. After several decades of analyzing the stomach contents of fulmars they found that in the early 1980s, 92 percent of the fulmars they tested had ingested on average 12 pieces of plastic. But by the late 1990s, 98 percent of bird stomachs contained an average of 31 pieces plastic.

Today, the world annually produces 250 billion pounds of plastic pellets that will become ingredients in cars, cell phones, computers, toothbrushes, medical equipment, Tupperware, gallon milk jugs, tape dispensers, children’s toys, CD cases, and thousands more. Most of that material becomes trash in a matter of years. Obviously, the enormous collection of plastic found in the Northern Pacific Gyre reflects our profligate and irresponsible trash-disposal techniques.

But the problem is not limited to improper disposal. Even the act of moving goods intercontinentally contributes to the problem. At least several thousand containers (estimated at between 2,000 and 10,000) fall from or are washed off giant container ships as they cross the oceans annually. Many of those containers hold materials that float, like plastic bath toys, or bags. In 1992, a container fell from a ship crossing the Pacific from Asia, releasing 28,800 toy ducks, frogs, turtles and beavers that floated across the Northern Pacific, washing onshore from Alaska to Japan; many made it even across the North Pole and into the North Atlantic. Also in 1992, five containers of Nike athletic shoes fell off a ship heading from South Korea to Seattle, resulting in 80,000 floating shoes, most of which washed up on beaches across the Pacific Northwest. And in 2002, Nike lost three more containers carrying 33,000 sneakers. To its credit, Nike is one of the few companies that have admitted that those incidents occur.

So, how did Great Pacific Garbage Patch form and what keeps it together, even if loosely? It all has to do with large-scale ocean currents called gyres. The term is derived from Latin, gyrus, which came from Greek, guros, meaning circle. Author’s Note: For those keen-eyed readers who are interested in birding, gyre is unrelated to the prefix, gyr, as in gyrfalcon, which is derived from the German word for vulture, which it borrowed from only God knows where. The word, gyre, is pronounced, jire, as in j-eye-r and rhymes with geyer. The name for the bird is pronounced, jir-fal-con, as in jeer.

In oceanography, the macro-scale (planetary) circulation system currents in each major ocean basin result from a combination of the global prevailing wind system (trade winds and westerlies/easterlies) and the Coriolis Effect in what is known as geostrophic flow. For example, a given parcel of water beneath the trade winds will attempt to flow at a right angle to the winds owing to the influence of the Coriolis Effect (Ekman motion theory describes the wind driven portion of circulation seen at the surface). However, that current will run into a small slope caused by Ekman transport (in the Atlantic Ocean that hill of water is about six feet high). And, since we all know that water does not readily run uphill, the end result is the Coriolis Effect and the pressure gradient force will attain a balance, causing the wind-driven current to flow around the hill of water, creating a gyre.

A somewhat simpler explanation is that these wind-driven eastward- and westward-flowing equatorial currents are blocked by the continents and rotate slowly in a clockwise direction in the North Atlantic and Pacific Oceans and in a counter-clockwise direction in the South Atlantic, South Pacific, and Indian Oceans, piling up water in the center. Structurally, all gyres consist of a narrow, swift-flowing western boundary current, an eastward-flowing zonal current, a broad and slow-moving eastern boundary current, and a westward flowing zonal current. Eight gyres (listed as A through H) have been identified by physical oceanographers.

A) The Brazil, South Atlantic, Benguela, and South Equatorial Currents form the Southern Atlantic Subtropical Gyre.

B) The Northern Atlantic Subtropical gyre consists of the Gulf Stream, Azores, Canary, and North Equatorial Currents.

C) The Labrador, North Atlantic, Irminger, and East Greenland Currents form the Northern Atlantic Sub-polar Gyre.

D) The East Australian, South Pacific, Peru/Chile, and South Equatorial Currents constitute the Southern Pacific Subtropical Gyre.

E) The Kuro Siwo, North Pacific, California, and North Equatorial Currents form the Northern Pacific Subtropical Gyre.

F) The Oya Siwo, Aleutian, California, and Alaskan Currents and the Alaskan Stream form the Northern Pacific Sub-polar Gyre.

G) A second sub-polar gyre is found in the Bering Sea.

H) The Agulhas, South Indian, West Australian, and South Equatorial Currents form the only subtropical gyre in the Indian Ocean.

Scientists at the National Oceanic and Atmospheric Administration (NOAA) predicted the eventual formation of the Great Garbage Patch in a paper published in 1988. That prediction was based on earlier research performed between 1985 and 1988 by several Alaska-based oceanographers that measured minute or microscopic plastic fragments in the North Pacific Ocean. That research demonstrated the presence of high concentrations of marine debris accumulating in ocean areas influenced by large-scale, prevailing circular currents known as gyres.

In 1997, Charles J. Moore was sailing through the North Pacific Gyre and happened across an enormous stretch of floating debris. Moore alerted the oceanographer Curtis C. Ebbesmeyer, who later named the region the Eastern Garbage Patch. Author’s Note: Ebbesmeyer spent much of his career monitoring ocean currents by tracking buoys and markers dropped at sea. But, in retirement he began using flotsam as markers and encouraged environmentalists to become involved in raising public awareness of the problem. For more details, see: Curtis C. Ebbesmeyer and W. James Ingraham Jr., “Pacific Toy Spill Fuels Ocean Current Pathways Research,” Eos (American Geophysical Union), September 13, 1994.

Not many of us associate gyres with garbage, but if you take a close look at what is happening in the Northern Pacific Subtropical Gyre you might experience an awakening. The Northern Pacific Subtropical Gyre churns slowly in a clockwise flow between the U.S. West Coast and Japan driven by a circular wind system that basically is heated at the Equator and cooled at the North Pole. Several large expanses of placid water are formed at the centers of two sub-gyres, one located between the Hawaiian Islands and California and the other between Hawaii and Japan. A few variants on an accurate but uncomplimentary nickname have been given to these placid waters: the Great Garbage Patch, the Western Garbage Patch, the Eastern Garbage Patch, and the Great Pacific Garbage Patch. The reason is clear since the arms of the gyre collect flotsam that eventually winds up in the calm, nearly current-less central section. With a geographic extent that may be more than twice the size of Texas, the Eastern Garbage Patch is no laughing matter. And not because of its size but because it has become a Mecca of floating plastics (and other debris). Oceanographic research has shown that parts of the Eastern Garbage Patch have about six times as much plastic by weight than plankton.

The other general meaning of the word, gyre, is a circular or spiral form; a closed curving plane equidistant from a fixed point, or objects shaped like a band, circle, disk, ring, or wheel. Fun Stuff: The meaning, spiral form, is used in the first stanza of the marvelous and oft-quoted poem by William Butler Yeats, The Second Coming.

Turning and turning in the widening gyre

The falcon cannot hear the falconer;

Things fall apart; the centre cannot hold;

Mere anarchy is loosed upon the world,

The blood-dimmed tide is loosed, and everywhere

The ceremony of innocence is drowned;

The best lack all conviction, while the worst

Are full of passionate intensity.

Most Destructive Earthquakes

The following list identifies the most destructive known earthquakes in the world on record in terms of loss of human life (50,000 or more) in order of the greatest number of deaths.[1] Note that the earthquakes with the greatest number of deaths and the lowest magnitude were in Haiti and China. The deaths were largely due to shoddy construction techniques and not the severity of the earthquake. Also note the huge range in deaths listed for the 1976 Tangshan earthquake. That range is not the result of poor reporting but rather the reluctance of the Chinese government to suffer public humiliation over the actual enormous loss of lives. Thus, the first number in the range is that reported officially by the government and the larger number is an estimate from more objective sources.

Date                                Location                             Deaths                        Magnitude

January 1556                    Shansi, China                      830,000?                             NA

January 12, 2010              Port-au-Prince                     316,000                               7.0

July 27, 1976                   Tangshan, China                 243,000-650,000                   7.5

December 26, 2004          Sumatra, Indonesia            300,000+                               9.2

October 1737                   Calcutta, India                     300,000                                NA

July 27, 1976                   Tangshan, China                 255,000+                             8.0

August 1138                    Aleppo, Syria                      230,000                                NA

May 22, 1927                   Xining, China                       200,000                               8.3

December 856+               Damghan, Iran                     200,000                                NA

December 1920               Gansu, China                      200,000                               8.6

March 893+                    Ardabil, Iran                         150,000                                NA

September 1923             Kwanto, Japan                    143,000                                 8.3

October 5, 1948              USSR                                   110,000                                7.3

September 1290             Chihli, China,                       100,000                                NA

October 2005                 Pakistan/Kashmir                 88,000+                               7.6

November 1667              Shemakha, USSR                80,000                                NA

November 1727              Tabriz, Iran                             77,000                                NA

December 1908              Messina, Italy                         70,000                                7.5

November 1755               Lisbon, Portugal                    70,000                                8.7

December 1932              Gansu, China                        70,000                                7.6

May 12, 2008                 Sichuan, China                      69,000+                              7.9

May 31, 1970                 Peru                                        66,000                               7.8

Month N/A 1268             Silicia, Turkey                        60,000                                NA

January 1693                 Italy, Sicily                              60,000                                NA

February 1783               Calabria, Italy                        50,000                                NA

June 20, 1990                Iran                                          50,000                             7.7

May 30, 1935                 Quetta, Pakistan                   30,000/60,000                     7.5

Real World Examples: On May 22, 1960, at 19:11 GMT, an earthquake occurred off the coast of South Central Chile that triggered a Pacific-wide tsunami with an epicenter of 39.5° S, 74.5° W and a focal depth of 33 kilometers. The number of fatalities associated with both the tsunami and the earthquake has been estimated to range from 490 to almost 2,300. What happened as a result of the earthquake (with a Richter magnitude of 9.6) was that a piece of the Pacific sea-floor near the coast of Peru, or strictly speaking part of the Nazca Plate that was about the size of California, dropped fifty feet. Like a spring, the lower slopes of the South American continent offshore snapped upwards as much as twenty feet while land along the Chile coast dropped about ten feet. This sudden deformation of the ocean bottom changed the shape of the sea surface. Since the sea surface likes to be flat, the pile of excess water at the surface collapsed and combined with the earthquake energy waves to create a series of waves that became the tsunami.

That seismic sea wave, together with the subsequent coastal subsidence and flooding, caused large-scale and widespread damage along the Chilean coast, killing about 2,000 people. As the waves spread outwards across the Pacific about 15 hours later they struck Hilo, Hawaii, where they built up to a height of thirty feet along the coast and caused 61 deaths along the waterfront. Seven hours later (22 hours after the earthquake) the tsunami hit the coastline of Japan, where ten-foot high waves caused 200 deaths. The waves also caused damage in the Marquesas, Samoa, and New Zealand. Tide gauges throughout the Pacific region measured anomalous oscillations for about three days as the waves oscillated from one side of the Ocean basin to the other.

The great Alaskan earthquake of 1964 was the largest earthquake in North America and the second largest ever recorded (largest occurred in Chile in 1960 as discussed above). The earthquake occurred at 5:36 pm on March 27, 1964, Alaska Standard Time. The epicenter was located in the Northern Prince William Sound about 75 miles east of Anchorage, or about 55 miles west of Valdez. The reported Richter magnitudes for that event ranged from 8.4 to 8.6. The moment magnitude (Mw) was reported as 9.2. The depth, or point where the rupture began, was about 14 miles within the Earth’s crust. The resulting seismic sea waves killed 110 people. Vertical displacement of the land surface caused by the earthquake affected an area of about 200,000 square miles and ranged from about 35 feet of uplift to seven feet of subsidence relative to sea level. The greatest absolute vertical displacement occurred at the southwest end of Montague Island, ranging from about 40 to 46 feet.

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[1] Source: U.S. Geological Survey National Earthquake Information Center. http://neic.usgs.gov/ and http://earthquake.usgs.gov/earthquakes/world/most_destructive.php