More Bolide Impact Information

Impact Glass

Glassy material produced by a complete or partial fusion of target rock by the heat generated from the impact of a large meteorite and occurring in and around the resulting crater; see tektite and shock metamorphism.

Impact Melt

During an impact event, a compression wave spreads outward from the point of impact. Engulfed by the shock wave, the colliding meteoroid and the surface rocks are melted and partially vaporized; see impact crater, tektite, and shock metamorphism.


Impactite

Slag-like glassy material ranging from glassy and vesicular to finely crystalline that was produced by complete or partial fusion of a host rock by sudden, powerful energy release caused by the impact of a large bolide. Impactites consist of both shocked and unshocked mineral grains and rock fragments and contain many spherules of iron-nickel specks. The rock is also known to collectors as Libyan Desert Glass; see impact crater, tektite, and shock metamorphism. Real World Example: Impactites can be found at the Ries Crater, Bavaria, Germany, as well as the Henbury Crater in central Australia and the Wabar Crater in the Rub’al-Khali, Saudi Arabia.

Shock Metamorphism

Process of irreversible chemical or physical alteration in rocks, minerals, and crystals by shock waves generated by bolide impact, extremely powerful volcanic explosion, or by the detonation of high-explosive or nuclear devices. These ultra-high pressure changes include: heterogeneous vesicular fused glass, planar features in quartz, planar features, and bent twins in feldspar, shatter cones, shock lamellae in mineral grains, kink bands in biotite flakes, quartz, and feldspars that have been completely transformed into diaplectic glass — glass formed at high-pressure in the solid-state in the feldspar minerals, especially plagioclase; the shock wave can break down the structure of the mineral, changing parts of it into glass that is isotropic, uniform in all directions — and creation of a high-pressure form of quartz called stishovite, a mineral that has never been found anywhere on Earth but around impact sites. Also known as impact metamorphism.

Shoemaker, Eugene M.

American geologist (1928-1997) whose passion was astrogeology; his contributions to that field and the study of bolides, impact craters, lunar science, asteroids, and near-Earth comets are legendary.[1] After graduating from California Institute of Technology in 1947 with a B.S. in geology at age 19, a year later he earned an M.S. and began working for the USGS. His first assignment was exploring for uranium deposits in Colorado and Utah. Those studies brought him geographically and intellectually in close proximity to the many volcanic features and the major impact structure on the Colorado Plateau in the western United States, specifically Hopi Buttes and Barringer (Meteor) Crater, which he became convinced was the result of a bolide impact. After being assigned by the USGS to study cratering at the Nevada nuclear weapons test site in 1956, he took a leave and entered the PhD program at Princeton University. In the period 1957-1960, he engaged in dissertation research that is today acknowledged as the classic study of the structure and mechanics of meteorite impact by comparing nuclear craters at the Nevada Test Site with the similar Barringer (Meteor) Crater in north-central Arizona, whose meteorite impact origin he established scientifically once and for all. That research — including the discovery of coesite (a high pressure form of silica created during bolide impacts) with Edward Chao — immediately became the definitive benchmark on basic bolide impact cratering. Immediately after that Shoemaker demonstrated the impact origin of the lunar crater Copernicus; mapped the Copernicus region using the principles of terrestrial geologic field mapping, thereby originating mapping methods that are still in use; established a lunar stratigraphic timescale; proved (with Edward Chao) the impact origin of the previously enigmatic Ries crater in Germany; created the Astrogeologic Studies Group within the USGS that was destined to take the lead in lunar studies and became its director; and gained international recognition for himself and his ideas at geological and astronomical conferences in Denmark and Russia. All that was accomplished before President John F. Kennedy established in May 1961 the landing of a man on the Moon as the goal of Project Apollo. It was a research focus that Shoemaker continued throughout his life, both through exploration of the Earth, specifically in Australia, and the planets by remote sensing and mapping. Without Shoemaker’s pioneering research, little would be known about the Moon’s geology or, probably, much else about its nature. At NASA Headquarters during 1962 and 1963 with high intensity and enthusiastic determination he successfully lobbied for the addition of a vigorous scientific program featuring geology to Apollo’s land-and-return goal. Although Addison’s disease[2] kept him from a lifelong dream of traveling to the Moon, Shoemaker initiated and vigorously promoted the intensive geologic training of the astronauts that made them capable scientific observers. He was a major investigator of the imaging by unmanned Ranger and Surveyor satellites which, before any Apollo landing, revealed the nature of the Moon’s cover of soil and broken rock, which he named the regolith. He led the field geology support teams for Apollos 11 and 12 but, intensely disappointed with NASA’s lagging commitment to science, returned to academic life as Professor and Chairman of Caltech’s Division of Geology and Planetary Sciences from 1969 to 1972. He culminated his lunar studies in 1994 with new data on the Moon from Project Clementine, for which he was the science-team leader. Tragically, Shoemaker was killed in a car accident in July 1997 in Australia while investigating meteor impact sites with his wife and professional colleague, Carolyn (an internationally famous astronomer, the discoverer of 32 comets, more than 800 asteroids and co-discoverer of the Shoemaker-Levy 9 comet). In a fitting tribute conceived by a former student, Eugene Shoemaker’s ashes were placed on-board the Lunar Prospector spacecraft, which successfully reached a polar mapping orbit around the Moon. After completing its scientific mission, the spacecraft impacted the Moon, scattering Shoemaker’s ashes across the lunar surface. During his lifetime Shoemaker’s pioneering research was recognized by at least 25 awards, including election to the National Academy of Sciences in 1980; the Day Medal of the Geological Society of America, awarded in 1982; the National Medal of Science, presented personally by President George H. W. Bush in 1992; and the American Geophysical Union’s Bowie Medal, awarded in 1996. Elected an AGU fellow in 1971, he served as President of the Planetary Sciences Section (1968-1970).

Tektite[3]

Group of silica-rich glassy objects that, although still poorly understood, are today thought by most scientists to be melt products of terrestrial rocks formed by hypervelocity impacts of large, extraterrestrial objects. They have no crystal structure and superficially resemble obsidian in appearance and chemical composition. However, several things distinguish these objects from obsidian. Primarily, they have a very low water content, a low alkali content, and they always contain lechatelierite (pure fused silica glass).They also often contain coesite (a highly dense silica polymorph), nickel-iron spherules, and baddeleyite (a zircon oxide mineral produced at very high temperatures during shock metamorphism), which lend evidence to a meteorite impact origin. In addition, many of the tektites found exhibit aerodynamic shapes, as if they were formed during flight. Relict mineral inclusions often yield information about the tektite parent material. Tektite sizes range from less than one millimeter to chunks 10-20 centimeters in width, with most being a centimeter or so in size, weighing a few grams, and are jet-black to dark green, although some have a yellowish tint.

Author’s Note: Tektites exhibit a wide array of sizes, shapes, and surface features. For example, splash forms include spheres, teardrops, dumbbells, discs, ablated forms also known as buttons, and chunks known as Muong Nong types that display a layered structure and are found primarily in Southeast Asia, hence the name. Real World Examples: Tektites are found in broad geographic bands, or strewnfields. Four of the major strewnfields are in Australia (where millions have been scattered over an area the size of Texas), Ivory Coast, Czechoslovakia, and North America. Strewnfields include tektites, which are found on land, and microtektites, which are microscopic tektites that have been found in deep-sea sediments.

Historical Background: Human association with tektites goes back to prehistoric times, when they were used as implements and ornaments. Tools made of tektites date to circa 4,000-6,000 BCE. After the Iron Age (500 BCE) tektites were frequently worn as good luck charms or as religious objects. The first reference in scientific literature appeared in 1788, when they were described as a type of terrestrial volcanic glass. In 1900, the famous geologist Eduard Suess coined the term tektite from the Greek tektos, meaning melted or molten. He was convinced that tektites were of an extraterrestrial origin and believed their shapes were caused by sculpturing due to high velocity air flow. He believed them to be glass meteorites and, because his work was highly read, people began referring to tektites as such. However, that idea was later rejected when no meteorites were found with compositions similar to that of tektites and when no evidence of cosmic ray exposure was found in tektites. The lack of cosmic ray exposure also led to the idea that tektites could not have evolved outside of the Earth-Moon system, since it indicated that the tektites’ time in space had to be less than 900-90,000 years, which is not long enough for anything outside an Earth-Moon system to travel to Earth. In 1917, the Austrian meteoriticist, Friedrich Martin Berwerth, discovered that tektites were similar chemically to certain sedimentary rocks, the first hint of terrestrial origins. The return of lunar materials from the Apollo missions in the late 1960s provided evidence that tektites are compositionally unrelated to lunar materials, which convinced the majority of scientists that tektites are terrestrial in origin and result from bolide impacts. See impact crater and Eugene M. Shoemaker for additional related information.

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[1] Sources: http://wwwflag.wr.usgs.gov/USGSFlag/Space/Shoemaker/GeneObit.html

http://cfa-www.harvard.edu/~marsden/SGF/shoemaker.html http://www.agu.org/inside/awards/geneshoemkr.html

[2] “. . . an endocrine or hormonal disorder that occurs in all age groups and afflicts men and women equally. The disease is characterized by weight loss, muscle weakness, fatigue, low blood pressure . . . and occurs when the adrenal glands do not produce enough of the hormone cortisol and, in some cases, the hormone aldosterone.” Source: National Institute of Diabetes and Digestive and Kidney Diseases http://www.niddk.nih.gov/health/endo/pubs/addison/addison.htm

[3] Source: D. M. Schneider: www.uark.edu/campus-resources/metsoc/techweb.htm

Bolide and Impact Crater

Bolide

Any large meteor, but especially in terms of our little world one that smashed into the Earth or the Moon. Real World Examples: Contrary to the once nearly universally accepted tenants of gradualism-uniformitarianism by mainstream geologists everywhere, today considerable evidence has been found indicating that meteors ranging from large to small once pounded the Earth with regularity. The 200-million-year old, 42 miles in diameter crater at Manicouagan, Quebec, is without doubt an eroded impact crater. The Chicxulub and Shiva Craters in the Gulf of Mexico and the Indian Ocean respectively are also very significant but not the only examples extent (see impact crater for more detailed descriptions). Other instances include what has been interrupted as a comet or asteroid string that fell in a straight line across what is now Illinois, Missouri, and Kansas about 320 mya, leaving as evidence eight craters in a row. Those impacts were not sufficiently large to trigger a global catastrophe such as the one that may have wiped out the dinosaurs (see mass extinction), but it would have caused considerable damage on a regional scale. The idea that bolide impacts often come in bunches, as comets or asteroids break up before impact, is exactly what some scientists say happened with the Chicxulub and Shiva Craters and what may have caused the mass extinction at the end of the Cretaceous period.

Impact Crater

Depression formed by the impact of an unspecified projectile, especially a crater formed on the Earth, another planet, or moon surface where the nature of the impacting body is not known. Impact craters form when an asteroid or comet (see bolide) strikes another, usually but not always larger body such as an asteroid, planet, or moon at high speed. These craters are classified as simple (relatively small with a smooth bowl shape and exhibiting a depth-to-diameter ratio of about one-to-six) or complex (large in diameter but shallow in depth with a depth-to-diameter ratio of between one-to-ten and one-to-twenty).

Images gathered by space probes have shown that the surfaces of the other inner planets (Mercury, Venus, and Mars) and their moons have been heavily bombarded by bolides. Because the Earth is very active geologically much of the physical evidence of impact craters has been removed or extensively modified by erosion and later tectonic activity. That said, over one hundred seventy impact craters have been identified on Earth and more are found each year as investigatory techniques improve. The impacting body generally melts (and frequently vaporizes if small enough) and the resultant materials mix with rocks at the impact site. Sometimes the impact site contains numerous siderophile elements such as iridium, osmium, platinum, and palladium as well as siderolites. Author’s Note: Other indicative signs of bolide impact are products of shock metamorphism (see that definition in the general category, metamorphism, types of): shatter cones, planar features in quartz, planar features and bent twins in feldspar, kink bands in biotite flakes, heterogeneous vesicular fused glass, quartz and feldspars that have been completely transformed into diaplectic glass (a type of glass formed solely by shock metamorphism), and a high-pressure form of quartz called stishovite, a mineral that has never been found anywhere on Earth except around impact sites.

Real World Examples: Meteor Crater (also known as Barringer Crater) in northern Arizona was formed between 20,000 and 50,000 years ago when a large meteor of nickel and iron, roughly 150 feet in diameter and weighing more than 60,000 tons, struck the Earth at a speed approaching 40,000 miles an hour, exploded and scattered molten debris for miles. Today, the Crater measures about three-fourths of a mile across and 530 feet deep. Its rim rises nearly 250 feet about the surrounding plain. Other large, complex impact craters include the Vredefort Ring in South Africa (with a diameter of about 155-185 miles), the Sudbury Astrobleme in Ontario, Canada (about 125-155 miles in diameter), and the Chicxulub structure in the Gulf of Mexico (> 110 miles in diameter).

The Manicouagan Ring Structure in northern Quebec, Canada, is one of the largest impact craters still preserved on the surface of the Earth. The diameter of the original rim is approximately 62 miles. A prominent 43-mile diameter, ice-covered, annular lake fills the inner ring where impact-brecciated rock has been eroded by glaciation. The causative impact occurred 214 mya, probably had a diameter of about three miles, and may have produced a mass extinction similar to that at the end of the Cretaceous period.

Wolf Creek Impact Crater in Australia is a relatively well-preserved, small impact crater that today is partly buried under wind-blown sand. The crater is located in an isolated area in the Great Sandy Desert of Western Australia, about 75 miles south of the town of Halls Creek, which is about 1,865 miles northeast of Perth. Its crater rim has a diameter of 2,400 feet, rising approximately 82 feet above the surrounding desert; the crater floor is 165 feet below the rim. Author’s Note: The age of the Wolf Creek crater’s is approximately 10,000-20,000 years, which means that since the first Aboriginals arrived in Australia around 40,000 years ago, their stories about its origin may not be fanciful.

Much closer to home is the Chesapeake Bay Impact Crater. Its discovery started with one of those utterly serendipitous occurrences with which science is blessed all too infrequently. In July 1983, a core sample taken about 90 miles east of Atlantic City, New Jersey, contained an unexpected present: a ten-centimeter-thick layer of late Eocene debris that proved to have been ejected from a massive bolide impact that had occurred somewhere around 35 mya. When the debris layer was analyzed it was found to contain microfossils and argon isotope ratios that revealed the ejecta were part of a broad North American impact debris field, previously known primarily from deposits in the Gulf of Mexico and Caribbean Sea. Since that time a lot has happened, including years of seismic reflection profiling, gravity measurements, and core drilling. The result is the source of that strewn field has been confirmed as a huge impact crater in and around Chesapeake Bay, which turned out to be the largest structure of its kind in the United States and the sixth-largest on Earth. The comet that crashed in what is now Chesapeake Bay most likely ranged from about one to two miles in diameter and was traveling at around 50,000 miles per hour prior to impact. It produced a crater 53 miles wide and fractured/collapsed bedrock to a depth of well over a mile. Today, those shattered rock structures continue to affect the pattern of groundwater flow throughout southeastern Virginia and southern Maryland. The force of the impact ejected enormous amounts of debris into the atmosphere and also generated gigantic seismic sea waves that extended far inland at elevations approaching 2,000 feet above sea level. Both effects probably killed most animals within several hundred miles of the impact site and the global atmosphere may have been so loaded with particulates that the entire Earth experienced a type of nuclear winter for many decades. Fossil and paleo-pollen evidence are still being analyzed, therefore, no definitive paleoclimatic effects have been documented. Today the results of that horrific impact more than 35 mya continue to affect the nearly two million people living in the region through subsidence, faulting, high-salinity groundwater in the coastal plain, and earthquakes around the crater’s perimeter.

Asphalt, Astrobleme, Batholith, Bathtub Effect, and Bog

Asphalt

Highly complex bituminous materials containing saturated and unsaturated aliphatic and aromatic compounds with up to 150 carbon atoms formed by the evaporation of volatile hydrocarbons. Asphalt ranges from dark brown to grayish-black and can be partially or nearly solid, semi-solid, or viscous. This cementitious material composed almost entirely of high molecular weight hydrocarbons and is found in oil-bearing strata and traps. However, its composition can vary depending on the source of the crude oil with which it is associated and can include varying amounts of sulfur, oxygen, and nitrogen as well as trace amounts of iron, nickel, and vanadium. Asphalt also occurs naturally in deposits known as asphalt lakes, which were most likely formed by the evaporation of larger quantities of petroleum at or near the surface. Asphalt occurs also as a natural mixture with sandstone or limestone strata and is known as asphaltic rock.

Real World Examples: The oil belt bordering the Orinoco River in eastern Venezuela is one of the principal regions in the world that yield the heavy material from which large amounts of asphalt can be manufactured. Citgo, which is owned by the Venezuelan company, Petróleos de Venezuela, has two East Coast asphalt plants, one in Paulsboro, New Jersey, and the other Savannah, Georgia, that rely totally on heavy Venezuelan crude. Citgo happens to be the dominant asphalt supplier in the eastern United States. The far greater majority of the asphalt used today is derived from petroleum distillation and is the heavy residue left after all the other lighter fractions (naphtha, gasoline, kerosene, etc.) have been removed. Very little commercial product is derived from other natural sources. When ignited, asphalt will burn with a smoky flame but leaves very little or no ash. Because of its intensely dark color, asphalt is used in the manufacture of paints, stains, and varnishes; however, its greatest worldwide use is as a road building material mixed with crushed rock or stone. That worldwide use relies on its remarkable waterproofing and binding properties. The hard surfaces of roads, for example, depend on the ability of asphalt to cement together aggregates of stone and sand. Author’s Note: Most asphalts are also efficient absorbers of light, which is why they are black. In the U.S. the word asphalt refers to the product that is known to the rest of the world as bitumen.

Historical Background: The first recorded use of asphalt as a road building material was in Babylon around 625 BCE, in the reign of King Nabopolassar. A cuneiform inscription on an ancient brick records that Processional Way, which led from the King’s palace to the north wall of the city, was paved with asphalt and fired brick. Not long after that, King Nebuchadnezzar II (604 BCE-562 BCE) constructed the Hanging Gardens for his homesick wife, who came from the forested mountains of what is now northern Iran. The name, Hanging Gardens, happens to be a poor translation of the Greek word for overhanging, as in the case of a vegetated terrace. The Greek historian and geographer, Strabo, who described the Hanging Gardens of Babylon in 1^st Century CE said: “It consists of vaulted terraces raised one above another, and resting upon cube-shaped pillars. These are hollow and filled with earth to allow trees of the largest size to be planted. The pillars, the vaults, and terraces are constructed of baked brick and asphalt.”

Another historical example of asphalt in Babylon was the famous Ishtar Gate, one of the eight gates of the inner city of Babylon, which was also built by the redoubtable and ever busy Nebuchadnezzar II (famous in the Bible for destroying Jerusalem, bringing the kingdom of Judah to an end, and dragging the Jews into exile). The double, fortified gate, constructed in about 575 BCE, was one of the most impressive monuments rediscovered in the ancient Near East. It was decorated with tiers of glazed brick bas reliefs of dragons and young bulls symbolizing the gods Marduk and Adad. The gate itself consisted of a double gate and on its south side was a vast antechamber. Through the gate ran the above-mentioned Processional Way. In part, the Dedicatory Inscription[1] on the Gate read: “Nebuchadnezzar, King of Babylon, the faithful prince and highest of princely princes,” blah-blah-blah, “the untiring governor, constantly concerned with the well-being of Babylon and Borsippa,” continued ceremonial bragging, “the wise, the humble, the caretaker of Esagila and Ezida, the firstborn son of Nabopolassar, the King of Babylon” . . .  yada yada yada . . . “pulled down the old gates and laid their foundations at the water table with asphalt and bricks and had them made of bricks with blue stone on which wonderful bulls and dragons were depicted. I covered their roofs by laying majestic cedars length-wise over them. I hung doors of cedar adorned with bronze at all the gate openings. I placed wild bulls and ferocious dragons in the gateways and thus adorned them with luxurious splendor so that people might gaze on them in wonder.” Fun Stuff: My bet is good old Nebu II watched all that hard work from the shade while getting friendly with one of his hundreds of curvy concubines and quaffing one of the early brewskis known to have been in style at that time while bitching, pissing, and moaning about the slowness of the workers.

The ancient Greeks were very familiar with asphalt and its properties. The word itself comes from the Greek asphaltos, meaning secure. The Romans modified the word to asphaltus and widened its use as a sealant for their baths, reservoirs, and aqueducts. Many centuries later, Europeans exploring the New World discovered natural deposits of asphalt in the New World. In 1595, Sir Walter Raleigh described a lake of asphalt on the Island of Trinidad, off the coast of Venezuela. Not one to ignore the material’s obvious utility, the industrious Brit used it to re-caulk his leaky ships and then took off for more adventures. That particular Asphalt Lake is still situated in the southwest peninsula of Trinidad. For centuries after its discovery by Raleigh it fascinated explorers, scientists, and thousands of ordinary, curious people. Research in the late 20^th Century by geo-scientists from Simon Bolivar University in Caracas, Venezuela, demonstrated that the Lake’s shape was not a three-dimensional bowl as had previously been thought but had an irregular shape, with a possible plug at the center. Their seismic research and modeling also indicated the existence of two large faults that are connected to the Los Bajos fault system to the south. Those two faults intersect at the asphalt outcrop and the asphalt seeps to the surface along the fault lines. About ten million tons of asphalt have been mined from the Lake since 1867. The refined product continues to be used on the island in the manufacturing and road surfacing industries.

Astrobleme

Circular erosional crater attributed to the impact of a bolide (meteorite or comet); meteor fragments, strange conical fracture patterns, and coesite (a super dense, high-pressure form of quartz) found in the rocks at astrobleme sites indicate an impact origin. Real World Examples: The most famous example may be the Sudbury Astrobleme in Ontario, Canada, an area with mines that supply about half the world’s nickel. Other well-known examples include Barringer Crater in Arizona (commonly known as Meteor Crater), Brent Crater in Ontario, and the Vredefort Ring in Orange Free State, South Africa. Author’s Note: No matter at what oblique angle the bolides intersect the Earth, the craters are always circular. Really. Check out the web site; it’s a treasure trove of fascinating information on the Vredefort Ring in South Africa: http://www.hartrao.ac.za/other/vredefort/vredefort.html. Fun Stuff: The word astrobleme is derived from Greek astron, star, plus blema, wound. Star wound, quite a romantic description for usually prosaic geo-scientists but all students of geoscience should know the term was coined by that most unusual and gifted geoscientist, Robert Dietz. Daffynition: Zit of enormous proportions universally feared by teenagers that erupts two or three days before prom night and totally resists all desperate attempts to pop it or disguise it with multiple layers of make-up. Author’s Rant: Been there, done that, don’t ever want to do it again since being a teenager sucks.

Batholith

Large irregular mass of coarse-grained, intrusive igneous rock exposed over an area of at least 60 square miles formed by the intrusion of numerous plutons in the same region or by wide-spread alteration of country rock through intense metamorphism Today most geoscientists believe that the innate buoyancy of batholiths is responsible for their formation and placement near the Earth’s surface. Because the magma in batholiths is less dense than that of the surrounding country rock, it gradually rises, essentially similar to the formation of salt domes in coastal Louisiana, which also deform plastically under heat and pressure.

Author’s Note: However, students should note the significant scientific disagreement as to the true nature of batholiths, especially with respect to the granite formation controversy. For several different theories and hot, juicy details concerning the formation of granitic batholiths, look up granitic magma in the overall definition of magma, origins of. Today, unlike when I was a young pup studying geology back in the day (1960s), most geoscientists no longer believe that batholiths are gigundous, bottomless masses. That said, there still is a good deal of controversy about batholiths and all that equally interesting intrusive stuff. The term is derived from combining the Greek, bathos, deep, and lithos, rock.

Fun Stuff: The next time you shake up a transparent bottle containing red wine vinegar and oil, watch what happens after the shaking stops and the fluid is allowed to sit for a few minutes. The oil migrates to the top and the heavier wine vinegar settles to the bottom. Now there’s an analogy to which most of us can relate without any trouble. Or watch the lumps in a lava lamp bubble up. But does that have anything to do with the formation of batholiths? Good question. The real answer: certainly not. But all analogies are only good if they kick-start your brain and get you thinking about whatever topic is puzzling you.

Real World Examples: The Sierra Nevada, Idaho, and Coast Range Batholiths are aligned along the west coast from south the north, respectively. Now, why do you think that is? You better be thinking about plate tectonics if you want to go very far in geoscience. In addition, one of North America’s best known batholiths is the Idaho Batholith of central Idaho and western Montana.

Bathtub Effect

Term and concept originated by John Sterman, an analyst of risk perception and management at the Sloan School at MIT. According to Sterman, injecting carbon dioxide and other gases into the atmosphere is analogous to pouring water into a bathtub whose drain is slightly open (absorption of gases by the ocean, etc.). Even if flow from the spigot is greatly reduced, the water level in the bathtub will not decrease because the outflow is so slow. Therefore, Sterman believes if you want to reduce the chances of passing dangerous climate alteration thresholds that may be irreversible then you have to reduce emissions to a point where accumulation stops and then cut emissions to reduce the amount of gases remaining in the “bathtub.” According to Sterman: “Stabilizing atmospheric concentrations requires emissions to fall to the net removal rate.” Which means simply stabilizing emissions is only the necessary first step toward stabilizing climate change and that changes to the climate caused by GHG emissions in the 20^th and 21^st Centuries may take up to 1,000 years to reverse. That precise point was made by Susan Solomon, et al, in a 2007 paper published in PNAS.[2]
Author’s Note: If you look at it another way, it’s a lot like a person who has a large credit card debt. Continuing to use the credit card increases the debt load but stopping new purchases does nothing to reduce the debt. You must first stop charging new debt and then pay more than the interest rate to stop debt accumulation. That and other analogies are not quite perfect since the reality of atmospheric emissions is quite complex. For example, even if we somehow totally stop injecting new GHGs into the atmosphere, the levels of those gases will continue to increase for up to 100 years and perhaps more because of the lag time it takes for those gases to work their way into the upper atmosphere.

Bog

Habitat that consists of waterlogged, spongy ground; standing body of water that typically is not fed by streams or underground fresh water springs. Bog water is usually cold, highly acidic, and low in oxygen. Various types of moss, especially Sphagnum moss, form a thick mat of floating plants at the edge of the bog and, over time, will expand to cover over the pond with a peat layer that may be firm enough to support bushes and even trees. Real World Examples: Although bogs are common in the American Northwest, western Canada, Ireland, Russia, and Scandinavia the ones you should be familiar with are the famous cranberry bogs of the American Northeast, especially in Massachusetts, New Jersey, Maine, and Nova Scotia.

Fun Stuff: Everyone who has read early American history knows that the colonies were England’s dumping ground for undesirables, a fairly loose classification that included religious dissidents, criminals (including a large number of bankrupt debtors), orphans, homeless and disposed people, political prisoners, and bond servants. Some of those miscreants were sent to New York and New Jersey and built smelting furnaces for bog iron (limonite) taken from the Peconic River and elsewhere. Many of the central and southern New England swamps and pinelands proved to be ideal sites for iron production. The peat soils provided the ore, nearby forests were used for charcoal, and oyster shells from the coast and native shell middens provided the calcium that was used as a flux. True to the spirit of American ingenuity, the production of iron soon wiggled out from under English control and the ever hated taxes. Local residents harvested the ‘iron plantations’ (otherwise known as peat bogs) and blacksmiths built their own smelters to provide for the needs of their communities. By the time of the Revolutionary War, smithies were producing a variety of war materiel for the colonies. Naturally, the Brits tried their damnedest to destroy every smelter and every blacksmithy they came across but in large part were unsuccessful.

By the early 1800s, the bog iron was gone. With the discovery of hard coal deposits and high-grade iron ore in Pennsylvania, the iron industry packed up and migrated west. Many landowners in the northeastern states were left with no income and an environment devastated by what were in essence open pit mines and by the loss of trees. One of the first plants to recolonize the damaged wetlands was Vaccinium macrocarpon Aiton, the lowly cranberry. The fruit had previously never been planted and harvested systematically. It wasn’t long before landholders in the New England states were transforming their relict bog iron plantations into profitable cranberry bogs. It was an early example of environmental restoration that was of economic value. Author’s Note: How many of those sitting down to a Thanksgiving meal realize that the cranberries on the table are a wonderful example of environmental restoration in action? Go figure.

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[1] Found online at: http://www.bible-history.com/babylonia/BabyloniaThe_Ishtar_Gate.htm

[2] Susan Solomon, et al. “Irreversible climate change due to carbon dioxide emissions.” PNAS; February 10, 2009, vol. 106, no. 6, pp.1704-1709.

Age of the Earth and Archimedes

        Age of the Earth  

          Although ancient rocks exceeding 3.5 Ga or giga-anni (billion years in age) are present on all continents, the oldest rock formations identified to date are the Acasta River gneiss, a granitoid-greenstone complex (dated around 4.03 to 4.06 Ga) in North West Territory, Canada, southeast of Great Slave Lake; and the Isua Supracrustal Formation in West Greenland (dated at 3.7 to 3.87 Ga). Other well-documented rocks nearly as old have been identified in the Minnesota River Valley and northern Michigan (3.5-3.7 Ga), the Pongola Supergroup in the Buffalo River gorge of South Africa and Swaziland (3.4-3.5 Ga), and in Western Australia (3.4-3.6 Ga). The ages of those rocks have been assessed by various radiometric dating methods; the consistency of the results provides scientific confidence that the ages are correct to within a few percentage points. An interesting feature of those ancient rocks is that they are not types of primordial crust but are lava flows and sediments that were deposited in shallow water, an indication that Earth history began well before those rocks were formed.
          In Western Australia, detrital and xenocrystic zircon crystals with U-Pb ages significantly older than 4 Ga have been found at five localities within the Yilgarn Craton in younger sedimentary rocks and have radiometric ages of about 4.35 to 4.4 Ga, making these tiny crystals the oldest materials to be found on Earth. The oldest specimen is from Jack Hills; its age of 4.404 Ga make it the most ancient fragment of the Earth’s crust that has been identified, formed approximately 150 million years after the planet itself, perhaps in an environment that contained liquid water and had considerably lower temperature than had been anticipated previously. That recent determination has profound implications in terms of the critical question as to when the Earth became habitable for life. Virtually all geoscientists agree that liquid water at or near the Earth’s surface was a prerequisite for the establishment of life. Consequently, if those environmental conditions are found by ongoing research to be as proposed, the Earth may have hosted life for as much as 700 million years longer than is currently believed. The best age for the Earth (4.54 Ga) is based on old, presumed single-stage leads coupled with the Pb ratios in troilite from iron meteorites, specifically the fragments found at Meteor Crater, Arizona.

          Author’s Note: Well, unless you’re firmly in the creationist camp, skipped over the above material, and have closed your mind to reason and rationality, the age of our Earth as established by various geosciences is approximately 4.6 billion years. But grasping the concept of the age of our planet really is not an easy task. Since thinking in conceptual terms about that ferociously long a time period is relatively fruitless and frustrating for most people, allow me to provide a more concrete example. Imagine those 4.6 billion years being squeezed down into a single year. In such a calendar, the time during which the first life-forms evolved (the Precambrian) would start January 1 and extend to about November 15, constituting more than five-sixths of all Earth history. No joke. For most of us, that’s quite a shock to our anthropocentric point of view. The age of invertebrates and primitive fishes, the Paleozoic, which extended from about 542 to 251 mya, would occupy the rest of November and part of December, or one-twelfth of the Earth’s age. The great age of the dinosaurs, the Mesozoic, which was from about 251 to 65 mya, would constitute most of the rest of December. The Quaternary, consisting of the Pleistocene and Holocene epochs or slightly less than two million years total, which would be equivalent to the time humans have spent on the Earth, would occupy only the last four hours on New Year’s Eve.

Archimedes[1]

          Famous Greek mathematician, 287 to 212 BCE, whose wide-ranging mind and pioneering ideas explored and expanded the worlds of physics, mechanics, and hydrostatics. He was famous for creating numerous geometric proofs using the rigid geometric formalism of Euclid, excelling especially at computing areas and volumes of spheres, cylinders, circles, and parabolas and was the first mathematician to correctly calculate the value of π.

          Historical Background: Few facts of Archimedes’s life are known with certainty but tradition has made at least two vignettes famous. In one story, he was asked by King Hiero II to determine whether a crown was pure gold or was alloyed with silver. Archimedes was perplexed, until one day, supposedly observing the overflow of water as he stepped into his bath, he suddenly realized that since gold is more dense (i.e., has more weight per volume) than silver, a given weight of gold represents a smaller volume than an equal weight of silver and that that given weight of gold would therefore displace less water than an equal weight of silver. Delighted at his discovery, he ran home sans clothes, shouting (perhaps apocryphally) “Eureka,” which means, “I’ve found it.” Let’s hope he was referring to the density theory rather than something more personal. When he showed that Hiero’s crown displaced more water than an equal weight of gold he proved the crown had been alloyed with another metal less dense than gold. We can only guess the jeweler’s unpleasant fate.

          In the other story Archimedes is said to have told Hiero II, illustrating the principle of the lever, “Give me a place to stand and I will move the world.” He invented extremely successful machines of war (in the Second Punic War in which Syracuse was allied with Carthage against Rome) so ingenious that Syracuse was able to hold off the besieging armies of Marcus Claudius Marcellus for three years (who was not only the commander of the Roman army but also the nephew of Caesar Augustus and his first designated heir, only to die before Augustus, plausibly from poisoning by someone who wanted the throne to go to another). When the city was taken, Marcellus supposedly gave orders to spare the scientist but Archimedes was killed nonetheless.

          Nine of Archimedes’s treatises, which demonstrate his discoveries in mathematics and in floating bodies, are extant. They are On the Sphere and Cylinder, On the Measurement of the Circle, On the Equilibrium of Planes, On Conoids and Spheroids, On Spirals, On the Quadrature of the Parabola, Arenarius (or Sand-Reckoner), On Floating Bodies, and On the Method of Mechanical Theorems. Archimedes’s many contributions to mathematics and mechanics include not only calculating the value of π but also devising a mathematical exponential system to express extremely large numbers (he said he could numerically represent the grains of sand that would be needed to fill the universe), developing the Archimedes principle, and inventing the Archimedes screw to move water from one elevation to another.

          Of particular importance to scientists and mathematicians in the 20^th and 21^st Centuries was the re-discovery of the Method of Mechanical Theorems manuscript, which had been thought to have been lost or stolen. In 1906 a palimpsest (a document written on recycled parchment, meaning the original material had been erased or otherwise removed) was brought to the attention of the great Danish philologist Johan Ludvig Heiberg, perhaps the greatest student of primary sources for classical Greek geometry, who studied it in Istanbul. He recognized the incompletely erased undertext of the parchment, which contained a collection of Greek Orthodox prayers, as the work of Archimedes, including portions of several works previously known from other manuscripts or translations, as well the Method, previously considered lost. Fortunately for science and history, Heiberg photographed the palimpsest because a few years later it disappeared in the fog of war surrounding World War I. But many of Archimedes’ words were illegible in the photos and many others were lost in the folds of the binding. Heiberg also had not copied Archimedes’s explanatory diagrams, which are crucial for understanding his thought processes.

          In October 1998, the manuscript surfaced again when Christie’s in New York City auctioned what they called the “Archimedes Palimpsest” to an unidentified American collector for $2,000,000. It was perhaps the most important single historical manuscript in the field of mathematics. The collector lent the manuscript to the Walters Art Museum in Baltimore, which is renowned for its rare book conservation department. Among many other things, analysis of the document revealed that Archimedes dealt with infinitely large sets, something that Greek mathematicians were reputed to avoid owing to its inherent difficulties.

In 2003-2004, Reviel Netz, a historian of science at Stanford University, and Nigel Wilson, a classics professor at Oxford University, concluded that Archimedes’s treatise, the Stomachion, was centuries ahead of its time. Netz and Wilson believe the work deals with combinatorics, a fiendishly difficult field involving combinations and permutations that did not come entirely into its own until the relatively recent rise of computer science.[2]

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[1] Source: Columbia Encyclopedia, 6^th Edition.

[2] For a fascinating article about Archimedes and the puzzle, see Erica Klarreich, “Glimpses of Genius Mathematicians and historians piece together a puzzle that Archimedes pondered,” Science News Online:

http://www.sciencenews.org/articles/20040515/bob9.asp and also see Stanford Report, November 6, 2002, found online at: http://news-service.stanford.edu/news/2002/november6/archimedes-116.html. See also Reviel Netz, Fabio Acerbi, and Nigel Wilson, (2004). Towards a Reconstruction of Archimedes’ Stomachion, Sciamus, 5, pp. 67-99.

Iron Deficiency and Oceanic CO2 Absorption

          As early as the 1930s, the potential role of iron as a limiting factor in phytoplankton productivity in the ocean was known to geochemists but was not understood. The conventional explanation for low phytoplankton productivity in certain parts of the oceans where high productivity would be expected was that grazing by zooplankton kept the phytoplankton ocean plants in check and prevented them from becoming too populous. Few oceanographers were happy with that explanation, which they thought was insufficient to fully account for the failure of phytoplankton in certain parts of the ocean to bloom into huge colonies.

          In the mid- to late-1980s, John Martin, an oceanographer at Moss Landing Marine Laboratories in California, proposed a controversial theory, that a lack of dissolved iron in the ocean kept populations of marine algae lower than normal and that seeding the ocean surface with iron should make phytoplankton multiply dramatically and absorb so much carbon dioxide, which is dissolved in the seawater, that the Earth’s atmosphere might thereby be cooled. Although Martin’s iron hypothesis excited some ocean scientists it caused great controversy as several prominent oceanographers stated that experimenting with the ocean was folly and involved treating the symptom without addressing the root cause, anthropogenic global warming. Other scientists resorted to less enlightening tactics, ridiculing Martin’s ideas as a Geritol solution. To quiet the criticism, Martin proposed something no previous oceanographer had done before: to conduct a laboratory experiment in the open ocean. But that idea proved even more controversial as it was opposed by many leading scientists who thought such a test would be dangerous to the ocean environment.

          The controversy soon became so heated that the National Research Council and the American Society of Limnology and Oceanography held national meetings to hear both sides. If either group decided that Martin’s idea was unethical or lacked scientific merit, Martin would have been denied funding to test the hypothesis. But to Martin’s relief, the scientists concluded that a small-scale experiment in the ocean wouldn’t threaten the environment and that the iron hypothesis should be tested. Although on June 18, 1993, Martin died from prostate cancer that had metastasized throughout his body, his experiment was carried forward in October of that year by Ken Johnson from Moss Landing Oceanographic Laboratories and Dick Barber of Duke University and scientists from several other universities. To the surprise of many oceanographers, the seeding of a 25-square mile ocean patch off the Galapagos Islands with iron crystals resulted in a three-fold increase of the chlorophyll levels in the water. Although it wasn’t the twelve-fold increase Martin had predicted, it was still a vindication of his ideas.

          In June 1995, Johnson and Kenneth Coale from Moss Landing Oceanographic Laboratories and 35 other researchers embarked on a second expedition to the eastern Pacific to replicate their first experiment. The team reapplied iron crystals twice and the results were dramatic. The scientists observed a 30- to 40-fold increase in chlorophyll levels, well beyond Martin’s prediction of a 12-fold increase. They also determined that particular characteristics of an overlying layer of water in the first experiment off the Galapagos Islands had reduced the effects of the iron. John Martin’s pioneering work had been vindicated.

Several recent research efforts by Kenneth Hutchins and David Bruland, beginning in the late 1990s (Nature, vol. 393, pp. 561-564, 1998) extended Martin’s ideas by attempting to determine exactly how iron deficiency in certain coastal and open-ocean areas inhibited the ability of sea water to store carbon dioxide. They knew that under ordinary conditions, iron enables phytoplankton to draw carbon dioxide from the atmosphere. That process enables ocean water to absorb about 80 times more carbon dioxide than is found in the atmosphere. However, in the absence of iron or with inadequate amounts of iron, that absorption process no longer is effective. As a result, phytoplankton growth is disrupted and the marine food chain is decimated from bottom to top, affecting life as small as bacteria and as large as whales.

          What Hutchins and Bruland found was that although those central California waters adjacent to the Big Sur in the Monterey Bay National Marine Sanctuary (later research confirmed their findings in coastal Peru and the Bering Sea) are rich in such plant “fertilizers” as nitrate, silicate, and phosphate, they contained insufficient iron to enable phytoplankton to use those nutrients through photosynthesis. Since iron-starved phytoplankton populations are unable to photosynthesize efficiently, the entire food chain that uses plankton in various ways as a type of sea-fodder is negatively affected. As a result, less food and energy are available to support predators large and small, across the gamut from cod, dolphin, tuna, marlin, sharks, and whales all the way to humans. That research is important because if near-shore waters fail to effectively absorb carbon dioxide owing to a lack of iron, geoscientists may need to revise existing carbon-cycling models and global climate-change models. Their work specifically demonstrated that iron availability controls the Si:N and Si:C ratios of diatoms, a finding that has been confirmed by many researchers working all over the world. That research has important implications for fields as diverse as algal physiology, carbon and nutrient biogeochemistry, global climatology, and paleoceanography.