The opinions expressed here are well-reasoned and insightful -- needless to say they are not the opinions of my employers

13 December 2010

AGU monday 12/13

Being at AGU reminds me that it's almost the solstice, and that the short days are coming to an end.

I went to John Holdren's lecture at lunchtime today. It was a listing of all of the ways that the President is the most pro-science chief executive we've had since, probably Jimmy Carter. Thing is, I don't really doubt that.

There are a number of sessions this week on communicating science. I'm going to a workshop tomorrow on "communicating climate change" hosted by several science bloggers and media types. I'm interested in what they have to say because we seem to be between a rock and a hard place, where the terms of the debate place us in an alien world where being in touch with reality counts against you.

I'm not a fan of Bjorn Lomborg, but he acknowledges the reality of human-caused climate change, he merely minimizes the potential consequences. To me, he represents one side of the debate. To the media and public, in a world where climate change deniers like James Inhofe hold power, Lomborg represents the sensible middle toward which we should all be migrating.

Anyway, I attended the Social Media Soiree this evening. It was wonderful to put faces to people who I knew only as names, aliases, or static photographs (said the South Park avatar). Jon Christensen (@westcenter) brought wine grown on serpentinite soil. I met Katharine North (@perrykid) and Dave Petley and reconnected with Callan Bentley, Brian Romans, and Andrew Alden. Lots of thoughtful discussions about the nature and value (and limitations) of social media. Thanks to Maria-Jose Vinas for organizing the soiree (and to the wine steward at the Intercontinental Hotel for allowing us to open the wine -- I assume he had to make sure it did not contain elevated levels of cadmium, nickel or fibrous chrysotile).

More education talks tomorrow, as well as the formation and evolution of Jovian moons and the UC Santa Cruz reunion party tomorrow night...

30 November 2010

Geo Tours in South Orange County: San Onofre State Beach

California is a geologist's paradise. In southern Orange County, opportunities for class field trips less than a half-hour from campus are abundant. A short drive up Silverado Canyon covers a significant fraction of the Mesozoic. We have world-class fossil beds in Mission Viejo with Miocene and Pliocene marine mammals and abundant shark teeth. Granitic mountains, active faulting, beaches backed by multiple marine terraces, Tertiary marine sedimentary rocks criss-crossed with recent andesitic and dacitic dikes, and the beaches are nice too...

For my geotour I present a basic outline of one of my class field trips: San Onofre State Beach, on the border of Orange and San Diego Counties, at the northern edge of the Camp Pendleton Marine Base. This is also the location of the San Onofre Nuclear Generating Station (SONGS), co-operated by Southern California Edison and San Diego Gas and Electric. Just to the south of the plant is the Cristianitos fault, an extensive fault whose proximity to the nuclear plant has in the past represented a source of controversy.

Topographic map showing the location of the trip. Note the significant change in the topography to the west of the Cristianitos fault. To the west of the fault the rock type is mostly the relatively soft San Mateo sandstone (Tsm). To the east of the fault (and northeast of the freeway) the rock is mostly the San Onofre Breccia (Tso). Below the freeway, east of the fault, the rock is the soft Monterey Formation (Tm) -- the softness of the rock is shown by the prevalence of slumping in this area.
A portion of the State of California geologic map of the San Onofre quadrangle. North of the freeway and east of the fault (gray) is the San Onofre Breccia (Tso); the tan is the Monterey Formation (Tm); the pink is the San Mateo Sandstone (Tsm); the pale yellow is the terrace deposits (Qal); and the canary yellow is the landslide deposits (Qls). Note again that the cliffs southeast of the Cristianitos fault are dominated by slumping.

The upper part of the exposed cliff face is alluvial deposits ranging from fine-grained material to coarse, matrix-supported flood gravels. These gravels represent some of the only metamorphic rock exposed in southern Orange County, including Franciscan blueschists and greenschists that have weathered out of the San Onofre Breccia.

The Monterey formation (Tm), exposed here along the beach, is a deep marine diatomaceous shale. To the right (south) is a recently failed block. The preservation of fine layering (below) indicates lack of bioturbation, typical in low-oxygen environments. this makes the Monterey formation an excellent source rock for hydrocarbons. The light-colored layer in the lower image is a volcanic ash deposit, dated by K-Ar to 15 Ma.

The Cristianitos fault (annotated image below). To the left is the 5 Ma San Mateo sandstone (Tsm), a poorly-cemented, coarse-grained shallow marine sandstone. On the right is the Monterey formation (Tm). Note the basal conglomerate (Qbc) stratigraphically below the alluvium but above both the Tsm and Tm.

The Monterey Formation is roughly 10 million years older than the San Mateo sandstone, but it has been brought into contact here by vertical movement of the Cristianitos Fault. Note that there is no offset of the basal conglomerate, indicating that the fault has not moved since the conglomerate was deposited. The conglomerate has been dated at approximately 100 Ka; since it shows no offset we can conclude that it has been at least that long since the Cristianitos Fault has been active.
Wide shot of the Cristianitos fault (annotated version below), showing the San Onofre Nuclear Power Plant 1 km to the north along the beach. If the fault had been active within the past 30,000 years, the plant could note have been built here.

06 November 2010

Don't Misunderestimate the Author

President Bush has apparently written and stated that the worst moment of his Presidency was when rapper Kanye West, in response to his lack of response to Hurricane Katrina, said of him: "George Bush doesn't care about black people."

I was taken by the total narcissism of this -- that in a Presidency that included almost 3000 Americans killed on 9/11, almost 2000 Americans killed in Katrina, a war in Iraq that, no matter how justified he felt in invading, led to the deaths of over 100,000 Iraqis over 5 years, a "war on terror" in which we've invented a new classification of POW that allows us to hold prisoners indefinitely and to torture them -- that the most "disgusting moment" was that someone said something bad about him.

Of course, he allowed himself to redefine what was said, claiming that Kanye had really called him a racist. He told Matt Lauer that "My record was strong I felt when it came to race relations and giving people a chance." See, he doesn't hate or fear black people. But that doesn't address the original statement. Does George Bush care about black people?

I believe that he, like all of us, cares about the people around him, people he knows personally, no matter the color of their skin. I also believe that his empathy tends to decay quickly with distance. Bush doesn't care about black people -- or anyone else who isn't part of his inner circle, especially middle class and poor people.

But the word "racist" sticks with me. The problem is that perhaps the conservatives are right -- it is, like Nazi, fascist, Hitler, socialist and "islamofascist" (a made-up word that has the dual properties of not making any sense and instilling great fear among the ignorant), it is so overused that it is losing all sense of meaning.

Are there racists among the Republicans? Are there sexists? Homophobes? Religious bigots? Yes to all of these, but the same could be said about Democrats and independents.

It is also true that the Republican Party, whether racist or not, seeks to exploit whatever racist, sexist, homophobic or religious bigotry they can find in the electorate.
As for former President Bush, I am willing to stipulate that he probably does not hate or fear any group because of its uniqueness any more or less than the average American.

In terms of his policies toward all of these groups however, and the policies of incoming group of Republicans, I believe a line Bill Maher used when referring to Dick Cheney applies:

"He doesn't hate children and puppies. They're just in the way."

11 August 2010

It’s Perseid Time!

The Perseids are one of the most watched meteor showers, partly because they generally put on a fantastic show and partly because they hit their maximum intensity every year in mid-August, when staying up and partying all night in the middle of the desert is relatively comfortable (the Leonids can put on a much bigger display but they peak in mid-November, so -- come on!).

I was going to do a post about where to go to watch them, when the peak times are (tonight and tomorrow are best, but it should be great this weekend), what to drink while you are watching, etc., but I’ll leave that to the actual astronomers and others...

The Perseids are most commonly associated with comet Swift-Tuttle, a short-period comet that reaches perihelion every 133 years. As the comet approaches the sun, sublimating gases erupt from the surface in huge geysers and carrying small grains of solids with them. These silicate particles can range in size from silt and sand size up to (in the rarest cases) pebbles and small cobbles. This “atmosphere” of gas and grains, though quite tenuous, can puff up to the diameter of a planet (or even the sun) around the comet’s nucleus, which may be as small as a few kilometers across. This can make some comets, under ideal conditions, among the brightest objects visible in the sky.

The anatomy of a comet

A tiny object like a comet cannot hold on to an atmosphere at all, much less one this size. As the solar wind pushes the material radially away from the sun, it breaks up into two components: the gases stream radially away from the sun creating the ion tail, which under ideal circumstances can exceed 1 AU in length. “Tail” is somewhat of a misnomer, as the generally more prominent ion tail always points away from the sun -- when the comet is moving away from the sun, its tail can lead the way!

Comet Hale-Bopp (1997) The blue tail is the ion (gas) tail and points radially away from the sun. The white tail is the dust tail and it curves to indicate the general direction of motion (right to left, tilted slightly toward the horizon.

The silicate particles of the dust tail, also under pressure from the solar wind, are affected more strongly by the sun’s gravity. The largest of these particles will fall into a solar orbit that more or less mimics that of the comet. These particles, known as meteoroids, can range in size from sand grains to pebbles to medium-sized cobbles, and the stream of meteoroids is known as a “dust trail” (as opposed to a “dust tail”).

The lifespan of any short period comet is limited -- each time it approaches the inner solar system it boils away a bit more, leaving fewer volatiles and smearing more of these meteoroids along its orbital path. If we are lucky enough, the Earth will cross this orbital path once or twice per year.

Earth moves at close to 30 km/s around the sun, and the portion of the dust trail in our path is moving at close to this speed (15 km/s to 45 km/s). So, depending on whether a meteoroid approaches us in retrograde or in direct it may hit the upper atmosphere at anywhere from 15-75 km/s. Interestingly, since we are moving counter-clockwise around the sun (viewed from the north pole) and rotating in the same direction, meteoroids we encounter closer to sunrise typically move faster than those we encounter near sunset.

It is a common (and logical) assumption that friction with the atmosphere will heat up the meteoroid. However, the heat is largely generated by the rapid compression of air molecules in front of the speeding particle. This process is called “ram pressure,” and this heat is largely responsible for heating the meteoroid, causing it to glow, melt and evaporate.

Perseid meteors

The grain becomes a meteor -- a “shooting star” -- when it is hot enough to become incandescent, usually at between 60 and 100 kilometers. As it streaks across the sky it evaporates, and the length of the trail depends on the size of the grain. Most meteors are no larger than a sand grain: pebble- and cobble-sized meteors, called “fireballs,” put on a much more impressive show, tumbling and shedding visible mass as they streak across the sky and are brighter than any object in the sky other than the sun or moon.

A fireball meteor

The Perseids are so called because they seem to radiate from a point located in the constellation Perseus. This is, of course, because we encounter the dust trail as we are moving in our orbit in the general direction of this constellation. This is the same effect as driving down a dark desert highway at night; the bugs generally are scattered and moving in random directions, but from the point of view of someone in a fast moving car, those bugs you encounter seem to radiate from a single point in front of your car.

At the peak of the shower (in the last few hours approaching sunrise) you may see up to a meteor per minute (in much more rare meteor storms you can see several or even dozens of meteors per minute). In the first few hours after sunset you have the best chance of seeing a few glowing fireballs, since Perseus is low in the sky and visible meteors will be hitting the atmosphere at a very low angle.

Most people are aware that you don’t need a telescope to watch a meteor shower, but a decent telescope (or, in a pinch, a good pair of binoculars) will be useful since Jupiter is close to opposition now and will be visible all night. Also, the other four naked-eye planets (Mercury, Saturn, Venus and Mars) are clustered together near the crescent moon. Tonight (August 11) Mercury and the moon will set simultaneously -- tomorrow it will set between Saturn and Venus, and on Friday night it will set after Mars.

07 August 2010

Little Boy

Note: I originally wrote this post in 2010, the 65th anniversary of the bombing of Hiroshima -- I have updated it here to fix some broken links.

"We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita; Vishnu is trying to persuade the Prince that he should do his duty, and to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another."

--J. Robert Oppenheimer, on witnessing the Trinity test

"Little Boy" was detonated above the city of Hiroshima on August 6, 65 years ago; the fission reactions took less than a microsecond to convert about 64 kilograms of uranium (enriched to 80% Uranium-235) into 63.5 kilograms of uranium plus 15-20 kilotons of energy.

It was only the second nuclear device detonated, after the Trinity test on July 15, and was unique in several respects: it was the first uranium weapon ever exploded; and the only gun-type" mechanism ever used -- both the Trinity device and the "Fat Man" bomb dropped several days later on Nagasaki were implosion-type weapons that used plutonium-239 as their fission target.

The bomb had several arming/switching mechanisms -- the first was a 15 second timer triggered by a wire when the bomb was released from the B-29 at an altitude of 31,000 feet, preventing it from accidentally detonating at too high an altitude; the second was a barometric switch that was triggered at an altitude of about 7000 feet; this triggered a radar altimeter, which sent out a weak signal toward the ground and set off the firing mechanism at an altitude of about 1900 feet (determined to be the altitude that would cause the greatest damage at the surface).

The firing mechanism was a converted artillery gun that fired an 18 centimeter long hollow cylinder, 16 centimeters in diameter with a 10 centimeter diameter opening, into an 18 x 10 centimeter round spike. The hollow cylinder contained just over 1.5 critical masses of enriched uranium (the hollow opening kept it below critical density) and the target spike contained just less than one critical mass. When the gun fired, the hollow cylinder traveled a few feet in 1/250th of a second, swallowing the solid spike and creating a single supercritical mass.

This type of firing mechanism had not been tested in a nuclear device, but it was such a simple mechanism that failure was considered a very low probability. It would only work with uranium though -- The fissile plutonium that was being manufactured in Tennessee and in Washington state fissioned too quickly to be combined over 0.004 seconds, so plutonium bombs required a much more complex implosion mechanism. This is the design that was tested three weeks earlier in the New Mexico desert, and was detonated on August 8th over Nagasaki. It was nicknamed "fat man" because of its spherical shape.

Spontaneous fission in uranium is rare -- a mass of this size will produce only a few hundred neutrons per second spontaneously; most of these
neutrons will go flying out of the mass with no effect, but a few will managed to bounce around the interior long enough to slow themselves down to thermal velocities ("slow" neutrons). 235U is somewhat unique among naturally occurring elements in that is can be induced to fission by the absorption of a slow neutron.

The extra neutrons are absorbed by a few 23
5U nuclei, causing them to wobble, destabilize, and split apart, creating two nuclear fragments roughly half the size of the original nucleus plus a couple of extra neutrons. These two neutrons are absorbed by two other uranium nuclei, causing them to split and generating four more neutrons, and so on... the reaction expands geometrically at incredible speeds, going through eighty generations of induced fissions in a microsecond. While this is occurring the bomb falls only an additional few inches.

Though the sum of the nuclear particles post reaction is the same, the sum of their masses is smaller by just over 1% -- about 600 grams of the material in the reaction is converted into energy by Einstein's equation, E=mc2. Some of this
energy goes to heating the bomb components, but most is released in the form of gamma rays and X-rays.

There is a blinding flash as the air immediately around the explosion is heated to millions of degrees. The expanding fireball reached a diameter of just over 1000 feet, cooling as it expanded, dropping to a temperature of only 4000°C at its outer edge. It is as if a new sun appeared in the sky, hundreds of times larger than our own sun. The superheated air causes materials at ground level to spontaneously burst into flame -- people, animals and plants are vaporized, leaving behind nothing more than carbon residue within a mile of ground zero.

The rapidly expanding air also generated a pressure/shock wave, a blast of wind moving outward at greater than the speed of sound. Within 2 miles around ground zero structural damage is near total. As this shock wave passed, pressure dropped momentarily to values close to the vacuum of space. The debris generated by the destruction also served to add fuel to the fires within this zone.

Though the secondary radioactive products of the fission reaction are dangerous, an air blast such as this one causes much of the physical debris of the bomb to dissipate through the atmosphere. There is however, a significant flux of gamma and neutron radiation at ground level. Immediate casualties due to radiation exposure were few; more victims died soon after of radiation sickness; the highest rates of casualties came later from increased rates of leukemia as well as other forms of cancer associated with radiation exposure.

Hiroshima (left) and Nagasaki (right)

By some accounts, Hiroshima was chosen as a target at least partly because it had been spared conventional bombing up to this point -- making it a "clean slate" for the study of the effects of the bombing, both during and after the event. Most of the data about the explosion itself was collected by a radio transmitter dropped by a plane flying in formation with the Enola Gay.

It was estimated at the time that 70,000 people died in the initial blast from the atomic bomb. By the end of 1945, deaths due to injuries, burns, radiation and other causes increased the death toll to 120-150 thousand. Some estimates put the number at 200 thousand by 1950. At least one study claims that 1 in 10 cancer deaths in victims since 1950 can be attributed to the bombing.

Though it has been 65 years since devices like these have been used as weapons, the ability to refine fuel (either enriched uranium or plutonium-239) has come within the technological capabilities of just about any country on Earth, and the design and manufacture of a working device is well within the abilities of a group of engineering grad students.

This video "1945-1998" represents the work of Japanese artist Isao Hashimoto and is a document of all 2053 known nuclear detonations on Earth during those years, shown by location at a rate of 1 month = 1 second.

28 July 2010

Accretionary Wedge #26: The Evolution of Geoblogs

This topic interests me because I’m very interested in how the collection, storage and dissemination of information has changed in less than two decades.

Douglas Adams gave a talk at a tech conference in Cambridge in 1998 (audio - transcript, in which he described the leaps in human knowledge in terms of the Four Ages of Sand (perhaps appropriate as Michael is co-hosting this month): The first two ages were the development of lenses for telescopes and then microscopes, allowing us to experience the universe at increasingly larger and smaller scales; the third was the invention of the silicon chip, allowing us to do calculations fast and therefore make increasingly complex models of reality; and the fourth is the use of computer technology to expand our notion of communication -- beyond the one-to-one version (dialog, either in person or by letter or phone) and the one-to-many version (books and newspapers, then radio and television) we’ve had for the last century -- into the present-day cacophony of many-to-many communication. Many-to-many communication allows individuals to interact with the world in something approximating real time.

I love the Ages of Sand metaphor, not just because it is geological, but because lodged into it is the idea that carbon-based lifeforms who have evolved on a mostly silicon-based planet have learned to exploit this common element in its oxide and elemental forms to exponentially enhance both our vision (ages 1 and 2) and our capacity to collect, process, store, and disseminate information (ages 3 and 4). We’re on the way to being a global, silicon-based organism.

We’re beginning to see some of the effects of many-to-many communication: a recent positive example is the success of the Green movement in Iran last year in getting their story heard by the rest of the world. A dozen or so years ago a dictatorship could shut down the news spigot pretty easily -- iconic images of Tank Man taken in Beijing during the 1989 pro-democracy demonstration exist because the events took place in front of the Beijing Hotel, where several photojournalists were staying, and they were able to smuggle film out (today that scene would have been recorded on dozens of individual mobile-phone cameras and seen world-wide within hours).

My first experience with a computer was writing the final report for my junior field geology class on my housemate’s Mac SE, in 1989. When I arrived at Santa Cruz for grad school students had pretty broad access to the campus dial-up network (No T1 lines in campus housing until 93-94), and we were downloading the Mosaic browser by the fall of 1993. My first reaction was that it was just Usenet with pictures, but back in 1989 I never figured the producers of the Simpsons would be able to generate enough stories to keep the show going for a year.

I first came across the geoblogosphere quite accidentally in April 2007 when a routine search for information on textbooks brought me to a post from Ron Schott, proposing a GeoWiki. It took me a month or so to discover and decipher GoogleReader -- today I’m subscribed to 60+ geoblogs and read pretty much every post. This organic community of geology-types, self-selected for relative tech-savviness, works for me on several different levels:

1. Education
A non-trivial number of geoblogospherians/geoblogospherlings are educators. Some are at two-year institutions, some at small colleges and universities, and some are grad students and undergrads (and a number have transitioned in the last few years). Like many of you, I had to go through a re-education process in order to teach classes of beginning students, at least partly because my understanding of the general curriculum was much deeper in some areas than in others. Discussing these issues with other educators (particularly those whose strong areas have complemented my weaker ones) has been a big help for me.

2. Community
What I miss most about being at a research institution is having day-to-day contact with friends and colleagues working in geosciences. I attend GSA and AGU most years, both to see old friends and to immerse myself in current topics. Geoblogger meetings are a new addition to this (and of course we now have Geotweeters as well!), but the geoscience folder on Reader and my Twitter account expose me daily to an informal discussion of the current state of research, issues in education and industry, real-time information on eruptions, earthquakes, mass movements, floods, and photos of what people are having for dinner.

3. News/context
Without the geoblogosphere we would still know about the Haiti earthquake, the Indonesian tsunami, the eruption of Eyjafjallajokull, and the Gulf oil volcano, but global events like these must be either catastrophic or affect Americans or Europeans to become "news" here. Sites like Geology News and Eruptions provide information and context to events that often disappear down the global news hole. And the level of expertise out there provides me with background that is quite useful when I interact with friends and students. A current example can be found in Dave Petley’s coverage of the Attabad landslide -- I’ve never been to the Hunza valley but Dave’s coverage has made this as real a geological (and teachable) event as it could be from 12,000 kilometers away.

4. Activism
Last year Kim at All My Faults was a prime mover in promoting the highly successful Donors Choose/Giving Kids the Earth program. This week Jessica at Tuff Cookie is promoting the International Volcano Monitoring Fund (please give, if only to spite Bobby Jindal). Out here in the west, the big (non-budget related) story has been the attempt to strip serpentine of its designation as California’s state rock. Among those trying to make sure that politicians make decisions based on solid science are Garry Hayes, Andrew Alden, Brian Romans (also @perrykid and @cbdawson in the twitterverse). It remains to be seen whether we win this, but this previously ignored bill is now drawing attention of major media outlets across the state as well as inside and outside the country, and supporting editorials in major newspapers.

A common refrain is that the computer and the internets are just tools -- perhaps, but in the same way that the wheel and pencil and steam engine are tools, not the way potato peelers and thigh masters are tools. Some tools change the world and the way we function in it and the way we think. Clay Shirky compares the invention of the printing press with the advent of online publishing. The former democratized the dissemination of information, and led to increasing rates of literacy and education but that wasn’t the intent. The rapid spread of literacy and individual access to the printed word that played a big role in creating our modern world from that ancient one is an emergent property of movable type -- what we are part of today seems to be a similar revolution and it is worth watching closely as it advances through the culture.

But keep in mind, I’m the one who didn’t think the Simpsons would last...

12 July 2010

In praise of green rocks

I've been following the hoopla/outrage over the California state legislature's latest intrusion into the byzantine world of state symbols for the past month, but have been reticent to dip my toes into the metaphorical waters -- I still feel bruised and abused over the battle between my beloved banana slug and the evil abalone for official state mollusk -- a battle that never so much ended as it dragged on into a stalemate, much like the Korean war (shut up, this is a great simile -- did you know that abalones are big supporters of Kim Jong Il?)...

Anyway, like Garry I have begun to compose a letter to the relevant assembly committees, members, and governators. I will print this out in multiple copies that will be sent out by snail mail, as my understanding is that no one pays more attention to your opinions than when you kill trees to express them (well, unless you give them lots of money).

For those who still read my rare ramblings, I'm interested in your input before I put this to bed. Some of the points have been made previously in this thread, though the only material I consciously cribbed was Chuck's points about talc formation and carbon sequestration:

Governor Schwarzenegger and Members of the Assembly and the Senate:

The California Legislature is currently considering a bill (Senate Bill 624) that would strip serpentine of its designation as the state rock of California, while declaring it to represent a hazard to the health of the state’s residents. I am writing to express my strong disagreement with this bill, and my dismay with some of the misguided or misleading arguments in support it. I am a graduate of both UC Berkeley and UC Santa Cruz, a professor of Geology at Saddleback College, and a member of the National Association of Geoscience Teachers, The Geological Society of America, and the American Geophysical Union, and while this letter represents my informed opinion as a scientist and educator, it does not necessarily represent the opinions of these institutions.

The rock serpentine (or serpentinite, the accepted geologic term for the rock) is commonly associated with the convergence of tectonic plates. It is formed from shallow mantle rocks (called “ultramafic” rocks) that have been altered by high-temperature fluids and then squeezed between two plates at (relatively) low temperatures. Outcrops of the rock are commonly pushed to the Earth’s surface along fault zones.

In California serpentinite is most common in the metamorphic belts of the Coast Ranges and in the Sierra Nevada foothills. The formation of serpentinite in our state is associated with the subduction of the Farallon Plate beneath the North American Plate beginning in the Mesozoic era and continuing until plate was completely consumed and the San Andreas Fault became active about 30 million years ago. Though it is found in many places in the world, the processes that brought it to the surface here have not occurred commonly so its abundance here is unique.

In the presence of water and CO2 serpentinite can produce the soft slippery mineral talc, the primary component of talcum powder. This reaction has been proposed as a hypothesis to explain why some major and minor faults or fault segments in California move gradually and do not produce large earthquakes. Its ability to absorb carbon dioxide makes serpentine one of the more promising geo-engineering sinks for this rising atmospheric gas.

The yellow-green to blue-green color commonly found in the serpentine minerals antigorite and lizardite, along with the polishing of the rock through movement along fault lines, produces beautiful exposures of jade-like rock in many areas. Serpentinite is a common decorative stone, used in countertops and tiles, and was a common choice, along with white marble, for columns and sculpture by Roman artists and architects.

The soils produced by the weathering of serpentinite lack certain elements (calcium, nitrogen, potassium, phosphorus) necessary for most plants, and are abundant in others (chrome, nickel, and selenium) that are poisonous to most plants. The process of evolution has led to unique plant communities found nowhere else but California. Trees such as the Jeffrey Pine and shrubs such as the Manzanita thrive on these soils. Because they have evolved to absorb heavy metals some of these plants have been used in the process of bioremediation.

The analysis of SB 624 “declares that serpentine contains the deadly mineral chrysotile asbestos and that exposure to it increases the risk of the cancer mesothelioma,” and “declares that California should not designate serpentine as the state rock due to its known toxic health effects.” Serpentinite is not a poisonous rock, at least not in the sense that exposure to natural outcrops of the rock represent a danger.

Rocks are agglomerations of several minerals, and though serpentinite is mostly made of antigorite and lizardite, chrysotile is another serpentine-group mineral that is sometimes present. Chrysotile is an “asbestiform” mineral, meaning that it grows crystals that are fibrous (i.e., thin and flexible). It shares this form and designation with several different minerals in the amphibole group, including amosite and crocidolite (neither of which is associated with serpentinite). Note here that the term “asbestos” refers not to a specific mineral or rock but to a particular crystal form that a few minerals take.

While the inhalation of any ground-up rock dust (i.e., silica or coal dust) is dangerous, because of their fibrous nature exposure to asbestos minerals can present significant health problems. Long-term exposure to asbestos minerals in the extraction or processing industries has been shown to represent a health hazard, the strongest correlations are associated with exposure to the amphibole group minerals; though most asbestos formerly used in construction was of the chrysotile variety, correlation between cancer and exposure specifically to chrysotile is not nearly as strong.

Let me emphasize here that I am not suggesting that asbestos exposure is not a health hazard nor am I suggesting that lung cancer and mesothelioma are not serious health problems that the state should concern itself with. These dangers to public health are established, and state law already deals with exposure to these materials.

My primary concern here is that this legislation expands that declaration to include not just industrial exposure to airborne chrysotile fibers but to casual exposure to unbroken bulk samples or outcrops of serpentinite itself (would I still be allowed to have hand samples of serpentinite in my classroom, or to pass them around to students in my lab?). It would be as if the state were to declare granite to be hazardous because it contains trace amounts of radioactive elements, or to eliminate the California Poppy as the official state flower (and to declare it represents a hazard) because it contains alkaloids related to opium and morphine.

Many citizens feel that the designation of an official state rock, mineral, flower, song, vertebrate or invertebrate fossil, etc., is a frivolous exercise with which state government should not concern itself. State Government has an important role, however, in promoting the appreciation of the state’s historical, cultural and natural attributes. For California educators our park system, our museums, and the acknowledgment of state symbols, whether it is the state rock, the state flower, the state motto, or the grizzly bear on the state flag (the state animal), provide a jumping-off point for the discussion of the geological, biological, and cultural wonderland in which we are privileged to live and work.


James L. Repka

Professor of Earth and Ocean Sciences

28 May 2010

Accretionary Wedge: Geo-image Bonanza!

I've chosen to share an image (okay, several images and a video) from the field locale for my dissertation, an area already familiar to many geobloggers.

38° 24' 14"N; 110° 56' 15"W; bearing 200°

After sorting through several images from this set, I've chosen this picture taken from the eastern peninsula of North Caineville Mesa, just east of Capitol Reef National Park in southern Utah. We're looking south toward the Fremont River floodplain (green) and South Caineville Mesa (opposite the river). The Henry Mountains are just out of frame to the east, and the horizon slopes upward to the west into the Aquarius Plateau. The pediment in the foreground is an inverted stream channel filled with sand and boulders from the cliffs. The photo below, taken from the floor of the badlands, looks in the opposite direction toward the mesa .

38° 23' 53"N; 110° 55' 18"W; bearing 330°

The Cretaceous Mancos shale dominates the images here. The mesas are topped by the Muley Canyon (formerly misnamed Emery) sandstone member, overlying the Blue Gate shale that forms the badlands. The Blue Gate member represents an interior sea and is rich in bentonite -- I've done some unintended camping here when caught in late summer storms, and spent the better part of a morning excavating Blue Gate shale from the wheel wells of our field van. Its usefulness in lining water wells, as an absorbing agent, and in drilling mud becomes obvious when you've seen a half-inch of wet, swollen clay separate a six inch puddle of rain water from bone-dry clay below.

I'm told it contains shark teeth, oysters, ammonites and even mosasaurs, but I spent 6 weeks a year working here for 4 years and never came across so much as a snail (of course the first time I brought students into the area one of them found one of the most beautiful ammonites I've come across in the field).

I came out here with my adviser, Bob Anderson, intending to look at incision rates in the badlands by doing cosmogenic exposure dating of the sandstone caps on the badland ridges and hoodoos, but the project eventually moved out of the badlands and onto the strath terraces along the Fremont River and an attempt to correlate terrace formation with climate cycles (again using cosmogenic radionuclides). My colleague Greg Hancock did a big portion of his thesis looking at incision processes on these badlands channels, including installing acoustic sensors to detect the rare flow events:

38° 23' 18"N; 110° 55' 52"W

I was going to leave you with this photo of Factory Butte, with the Waterpocket fold in the background but I remembered this clip from the dailies of the never-completed movie "Dark Blood," a scene shot several days before the death of River Phoenix...

38° 23' 24"N; 110° 54' 45"W

24 January 2010

How big was that one?

Every semester I spend time explaining the methods of measuring earthquakes to students. I explain magnitude, with a primer on how logarithms work. I talk about the limitations of the Richter scale in measuring larger quakes, as more energy is released at low frequencies, and how the Seismic Moment, though more difficult to calculate, provides a better snapshot of the released energy.

I always emphasize that intensity, as represented by surface wave amplitudes, frequencies and ground acceleration, is a more useful way to describe how earthquakes affect communities. Magnitude has the advantage though, in that it can be reported as a single number. This creates a problem in the way the general public perceives earthquakes, a problem addressed in this post I came across a few days ago.

The earthquake in Haiti, for instance, had a
magnitude of 7.0. Everyone understands that this is bigger than a magnitude 6.7, like Northridge, but few understand that the difference means that the Haiti event released three times the seismic energy of the Northridge earthquake.

And while building codes and construction standards play a big role in determining relative damage and casualties, this is often overplayed. After the 2001 Nisqually earthquake in Washington (Mw=6.8), there were commentaries in the news media suggesting that the lack of serious damage and casualties in Washington reflected poorly on standards in LA, where the Northridge event killed 67 people and caused extensive damage. Of course the primary reason for the difference is that the Nisqually earthquake occurred at a depth of 52 kilometers, versus 19 km in Northridge.

The author of the above post suggests a change in terminology, that when geologists talk to the media about earthquakes they refer to the seismic energy relea
sed by an earthquake (in tons of TNT, rather than joules of course). This would be roughly equivalent to reporting the seismic moment (Mo) rather than the moment magnitude which, is just a way of correlating the seismic moment with the Richter Magnitude.

Of course the 2004 Sumatra earthquake (Mw=9.1) released 1400 times more energy than Haiti, yet the death toll in Haiti has exceeded 100,000 and may approach the quarter million that were lost in 2004 (though most of those deaths were attributable not to the earthquake but to the tsunamis that crossed the Indian ocean as a result). As with the Northridge/Olympia example above, the Haiti earthquake had a focus just 13 km beneath the most densely populated region of Haiti, while the Indian ocean quake was 30 km deep and hundreds of kilometers from the nearest populated area (of course it also displaced the floor of the ocean by approximately 30 meters, generating the tsunami).

My suggestion would be to scale the seismic moment to the distance between the earthquake's focus and the nearest populated area (where energy decreases with distance squared). This does not take into account that a significant portion of energy is released as heat and deformation of materials. It also ignores the complexities of subsurface geology and the unique character of individual focal mechanisms. But I think it would go a long way toward expressing to the general public the relative seriousness of different earthquakes.

Here are a couple of back-of-the-envelope examples. In Haiti, Olympia and Northridge I've scaled only for depth, as the foci were more-or-less directly beneath the affected populations. I begin with the assumption that a magnitude 4 event is the energy equivalent of 1 kiloton of TNT:

Update: Hypocentre contacted me below and pointed out my math errors, which have been corrected in the table.

Though the actual mechanics, geology and secondary effects (such as tsunami and landslides) are different in each situation, these adjusted energies seem to be a reasonable approximation of the casualties and damage for these six earthquakes.

I think this is a relatively easy adjustment to make in reporting events, and conveys much more information to the public than the current method. I'm interested in people's comments...


***Note that the IRS has been instructed to allow tax-deductible donations to Haitian relief made in the current year to be deducted on your 2009 taxes. Give generously.

Red Cross
Oxfam America
Doctors Without Borders

Contact Me

You can send me email at jrepka@saddleback.edu