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  • Carbonatites are strange igneous rocks made up mostly ofcarbonates – common minerals like calcite, calcium carbonate. Igneous rocksthat solidify from molten magma usually are high-temperature rocks containinglots of silicon which results in lots of quartz, feldspars, micas, andferro-magnesian minerals in rocks like granite and basalt. Carbonatitescrystallize from essentially molten calcite, and that’s really unusual.

    Most carbonatites are intrusive, meaning they solidifiedwithin the earth, and it wasn’t until 1960 that the first carbonatite volcanoerupted in historic times, proving that they form from cooling magma. Theeruption at Ol Doinyo Lengai in Tanzania occurred on a branch of the EastAfrican Rift System, and most carbonatites are associated with these breaks incontinental crust where eventually a new ocean may form.

    Mt Lengai, Tanzania, photo by Clem23
    (Creative Commons License - source)Eruptions at Lengai, whose name means “mountain of god” inthe Maasai language, are the lowest-temperature magmas known because calcitemelts at a much lower temperature than silica-rich compounds, around 510degrees C versus 1000 degrees or more for most magmas. It isn’t even red-hotlike most lava flows.

    A simple and early interpretation of carbonatites was thatthey represented melting of limestone, but geochemical data indicate that theyreally do come from primary igneous material that probably originated in themantle. Exactly how they form is debated, in part because they are so rare, butone idea is that they result from special cases of differentiation within morecommon magmas, or maybe an example of certain chemicals – the carbonates – separatingout in an unusual way.

    Another unusual aspect of carbonatites is the mineralsassociated with the dominant calcite. It’s common to get rare-earth compounds,tantalum, thorium, titanium, and many other minerals that are unusual in highconcentrations in other settings. The Mountain Pass rare-earth deposit inCalifornia, once the largest producer of rare earths in the world, is in aPrecambrian carbonatite. Rare earths are used in lots of modern technologies,including turbines for wind energy, batteries in electric car motors, cellphones, solar cells, and eyeglasses.

    Rare earths are also produced from the Mt. Weld carbonatitein Western Australia, but it’s more famous for its tantalum, an element that’svital in capacitors for cell phones, video games, and computers. Australia hasby far the greatest reserves of tantalum, but mining didn’t begin until 2011and production is just now ramping up. The United States, which is 100%dependent on imports for tantalum, imports most of it from Brazil, Rwanda,China, and Kazakhstan.

    Magnetite is a common associated mineral in carbonatites,and at Magnet Cove, Arkansas, there’s enough to give the name to the place. It’salso rich in titanium, often in the form of the mineral rutile, titanium dioxide.When I was there on a geology field trip in 1969, I remember walking into theKimzey Calcite Quarry. It was like walking into a giant calcite crystal, withgigantic cleavage faces the size of a person or bigger. We collected lots of coolrutile and pyrite crystals.

    More common economic minerals can be associated withcarbonatites as well. At one in South Africa the main products are copper andvermiculite.

    While I said earlier that carbonatites are really rare,there are still a few dozen known. It’s possible that their rarity is areflection of the fact that calcite is much more easily eroded and dissolvedthan the typical basaltic rocks that derive from most volcanoes, so they maysimply be poorly preserved.

    —Richard I. Gibson




  • As near as I can tell in the original daily series in 2014,I never addressed the topic of turbidity currents and their sedimentaryproduct, turbidites. But they account for the distribution of vast quantitiesof sediment on continental shelves and slopes and elsewhere.

    You know what turbid water is: water with a lot of suspendedsediment, usually fine mud particles. In natural submarine environments,unconsolidated sediment contains a lot of water, and when a slurry-like packageof sediment liquifies, it can flow down slopes under gravity, sometimes forhundreds of kilometers.

    It isn’t correct to think of these streams of water andsediment as like rivers on the sea floor. Rivers transport sediment, whetherboulders or sand or silt or mud, through the traction, the friction of themoving water. Turbidity flows are density flows, moving because the density ofthe water-sediment package is greater than the surrounding water. That meansthey can carry larger particles than usual.

    Turbidite formation. Image by Oggmus, used under Creative Commons license - source
    Sometimes a turbidity flow is triggered by something like anearthquake, but they can also start simply because the material reaches athreshold above which gravity takes over and the material flows down slope. Theamount and size of sediment the flow can carry depends on its speed, so as theflow diminishes and wanes, first the coarse, heavier particles settle out,followed by finer and finer sediments. This results in a sediment packagecharacterized by graded bedding – the grain size grades from coarse, withgrains measuring several centimeters or more, to sand, 2 millimeters andsmaller, to silt and finally to mud in the upper part of the package. Repeatedturbidity flows create repeated sequences of graded bedding, and they can addup to many thousands of meters of total sedimentary rock, called turbidites.

    Other sedimentary structures in turbidites can includeripple marks, the result of the flow over an earlier sediment surface, as wellas sole marks, which are essentially gouges in the older finer-grained top of aturbidite package by the newest, coarser grains and pebbles moving across it.

    There are variations, of course, but the standard package ofsediment sizes and structures, dominated by the graded bedding, is called aBauma Sequence for Arnold Bouma, the sedimentologist who described them in the1960s.

    Turbidity currents are pretty common on the edges ofcontinental shelves where the sea floor begins to steepen into the continentalslope, and repeated turbidity flows can carve steep canyons in the shelf andslope. Where the flow bursts out onto the flatter abyssal sea floor, hugevolumes of sediment can accumulate, especially beyond the mouths of the greatrivers of the world which carry lots of sediment.

    When the flow is no longer constrained by a canyon or even amore gentle flow surface, the slurry tends to fan out – and the deposits arecalled deep abyssal ocean fans. They are often even shaped like a wide fan,with various branching channels distributing the sediment around the arms ofthe fan. The largest on earth today is the Bengal Fan, offshore from the mouthsof the Ganges and Brahmaputra Rivers in India and Bangladesh. It’s about 3,000km long, 1400 km wide, and more than 16 km, more than 10 miles, thick at itsthickest. It’s the consequence of the collision between India and Eurasia andthe uplift and erosion of the Himalaya.

    The scientific value of turbidites includes a record oftectonic uplift, and even seismicity given that often turbidity currents aretriggered by earthquakes. They also have economic value. Within the sequence offining-upward sediments, some portions are typically very well-sorted, cleansandstones. That means they have grains of uniform size and shape and not muchother stuff to gum up the pores between the sand grains – so that makes thempotentially very good reservoirs for oil and natural gas. You need the properarrangements of source rocks, trapping mechanisms, and burial history too, butdeep-water turbidites are explored for specifically, and with success, in theGulf of Mexico, North Sea, offshore Brazil and West Africa, and elsewhere. TheMarlim fields offshore Brazil contained more than 4 billion barrels ofproducible oil reserves when they were discovered in the 1980s.

    Ancientturbidites sometimes serve as the host rocks for major gold deposits, such asthose at Bendigo and Ballarat Australia, which are among the top ten goldproducers on earth.

    —Richard I. Gibson



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  • This episode is about some of the interestingconnections that arise in science.

    We’ll start with me and my first professional job as amineralogist analyzing kidney stones. My mineralogy professor at IndianaUniversity, Carl Beck, died unexpectedly, and his wife asked me as his onlygrad student to carry on his business performing analysis of kidney stones. Beckhad pioneered the idea of crystallographic examination to determine mineralogyof these compounds because traditional chemical analysis was misleading. For example,some common kidney stones are chemically calcium phosphates and calciumcarbonates – but they are hardly ever calcium carbonate minerals. That makes abig difference in terms of treatment, because calcium carbonate minerals can bedissolved with acids, while calcium phosphate cannot. The carbonate is actuallypart of the phosphate mineral structure, partially substituting for some of thephosphate. Other subtleties of mineral crystallography can distinguish between differentminerals and can point to specific kinds of treatments, more than justchemistry can.

    One of the most common minerals in kidney stones is calledwhewellite – calcium oxalate, CaC2O4 with a water molecule as part of its structure.In kidney stones it usually forms little rounded blobs, but sometimes the waythe mineral grows, it makes pointy little things called jackstones, for theirsimilarity to children’s’ jacks. And yes, those can be awfully painful, or so I’mtold.  Whewellite is really rare in thenatural world beyond the urinary system, but it does exist, especially inorganic deposits like coal beds. Whewellite was named for William Whewell,spelled Whewell, a true polymath and philosopher at Cambridge University inEngland during the first half of the 19th century. He won the RoyalMedal for his work on ocean tides and published studies on astronomy,economics, physics, and geology, and was a professor of mineralogy as well.

    Mary Somerville, 1834 painting by
    Thomas Phillips - sourceWhewell coined many new words, particularly the word “scientist.”Previously such workers had been called “men of science” or “naturalphilosophers” – but Whewell invented the new word scientist for a woman, MarySomerville. Somerville researched in diverse disciplines, especially astronomy,and in 1835 she became one of the first two female members of the RoyalAstronomical Society, together with Caroline Herschel, discoverer of manycomets and nebulae.

    In 1834 Somerville published “On the Connexion of thePhysical Sciences,” a synthesis reporting the latest scientific advances inastronomy, physics, chemistry, botany, and geology. William Whewell wrote areview in which he coined the word scientist for Somerville, not simply toinvent a gender-neutral term analogous to “artist,” but specifically to recognizethe interdisciplinary nature of her work. And even more, according to Somerville’sbiographer Kathryn Neeley, Whewell wanted a word that actively celebrated “thepeculiar illumination of the female mind: the ability to synthesize separatefields into a single discipline.” That was what he meant by a scientist.

    Somerville was born in Scotland in 1780 and died in 1872 atage 91. Her legacy ranges from a college, an island, and a lunar crater namedfor her to her appearance on Scottish bank notes beginning in 2017. Besides themineral whewellite, William Whewell is also memorialized in a lunar crater andbuildings on the Cambridge campus, as well as in the word scientist, includedin the Oxford English Dictionary in 1834, the same year he coined it. He diedin 1866.

    —Richard I. Gibson
    LINK:Article about Whewell and Somerville 



  • Today we’re going back about 280 millionyears, to what is now Uruguay in South America.

    280 million years ago puts us in the early part of thePermian Period. Gondwana, the huge southern continent, was in the process ofcolliding with North America and Eurasia to form the supercontinent of Pangaea.South America, Africa, Antarctica, India, and Australia had all been attachedto each other in Gondwana for several hundred million years, and the extensiveglaciers that occupied parts of all those continents were probably stillpresent in at least in highlands in southern South America and South Africa, aswell as Antarctica.

    But the area that is now in Uruguay was probably in cool,temperate latitudes, something like New Zealand or Seattle today. Theconnection between southern South America and South Africa was a lowland,partially covered by a shallow arm of the sea or perhaps a broad, brackishlagoon at the estuary of a major river system that was likely fed in part byglacial meltwater from adjacent mountains. We know the water was shallowbecause the rocks preserve ripple marks produced by wave action or currents.

    The basin must have been near the shore because delicatefossils such as insect wings and plants are among the remnants. It looks likethis shallow sea or lagoon became cut off from the ocean, allowing the watersto become both more salty, even hypersaline, and anoxic, as the separationrestricted inflows of water, either fresh or marine, that could have continuedto oxygenate the basin. In the absence of oxygen, excellent preservation ofmaterials that fell to the basin floor began, and there were few or noscavenging animals to disrupt the bodies.

    The rocks of the Mangrullo Formation, as it’s called today,include limestones and siltstones, but the most important for fossilpreservation are probably the extremely fine-grained claystones and oil shales.These rocks contain some of the best preserved fossil mesosaurs known anywhere.That’s mesosaurs, not the perhaps more well-known mosasaurs, which are largewhale-like marine reptiles that lived during Cretaceous time. Here, we’re inthe Permian, well before the first dinosaurs.

    Mesosaur by Nobu Tamura (Creative Commons license & source) 
    Mesosaurs were aquatic reptiles, and they are the earliestknown. They evolved from land reptiles and were among the first to return tothe water to adopt an aquatic or amphibious lifestyle. They were once thoughtto be part of a sister group to reptiles, a separate branch of amniotes, whichare animals that lay their eggs on land or bear them inside the mother, likemost mammals do. In that scheme, mesosaurs and reptiles would have divergedfrom a common, earlier ancestor. But more recent studies categorize them asreptiles that split off from the main genetic stem early in the history of theclass, so they’re pretty distant cousins to dinosaurs and all modern reptiles,but they’re still reptiles. There is ongoing debate among evolutionarypaleontologists as to exactly where mesosaurs fit.

    The fossils in Uruguay are so well preserved that we canidentify the gut materials of mesosaurs, and we know they mostly atecrustaceans, aquatic invertebrates related to crabs, shrimp, and lobsters. Thepreservation is so exceptional that in some cases, soft body parts arepreserved including major nerves and blood vessels in mesosaurs and stomachsand external appendages in the crustaceans. The earliest known amniote embryosalso come from these fossil beds.

    Mesosaurs had a short run in terms of their geologichistory, only about 30 million years. They were extinct about 270 million yearsago, well before the great extinction event at the end of the Permian, 250million years ago. But the presence of coastal-dwelling mesosaurs in both SouthAmerica and Africa was a contributing idea in the early development of thetheory of continental drift, since it was presumed that they could not havecrossed the Atlantic Ocean as it is today.

    —Richard I. GibsonLinks:Piñeiro et al. 2012 Environmental conditions Paleogeography from Ron Blakey 


  • Today we’re going to the Mountains of theMoon – but not those on the moon itself. We’re going to central Africa.

    There isn’t really a mountain range specifically named theMountains of the Moon. The ancients, from Egyptians to Greeks, imagined orheard rumor of a mountain range in east-central Africa that was the source ofthe river Nile. In the 18th and 19th centuries,explorations of the upper Nile found the sources of the Blue Nile, White Nile,and Victoria Nile and identified the Mountains of the Moon with peaks inEthiopia as well as 1500 kilometers away in what is now Uganda. Today, therange most closely identified with the Mountains of the Moon is the RwenzoriMountains at the common corner of Uganda, the Democratic Republic of Congo, andRwanda.

    This location is within the western branch of the EastAfrican Rift system, an 8,000-kilometer-long break in the earth’s crust that’sin the slow process of tearing a long strip of eastern Africa away from themain continent. We talked about it in the episode for December 16, 2014.
    The long linear rifts in east Africa are grabens, narrowdown-faulted troughs that result from the pulling apart and breaking of thecontinental crust. The rifts are famously filled in places by long, linear riftlakes including Tanganyika, Malawi, Turkana, and many smaller lakes.

    Virunga Mountains (2007 false-color Landsat image, annotated by Per Andersson : Source)
    When rifting breaks the continental crust, pressure can bereleased at depth so that the hot material there can melt and rise to thesurface as volcanoes. In the Rwenzori, that’s exactly what has happened. The Virungavolcanoes, a bit redundant since the name Virunga comes from a word meaningvolcanoes, dominate the Rwenzori, with at least eight peaks over 10,000 feethigh, and two that approach or exceed 4,500 meters, 15,000 feet above sealevel. They rise dramatically above the floors of the adjacent valleys andlakes which lie about 1400 meters above sea level.

    These are active volcanoes, although several would beclassified as dormant, since their last dated eruptions were on the order of 100,000to a half-million years ago. But two, Nyiragongo and Nyamuragira, have eruptedas recently as 2002, when lava from Nyiragongo covered part of the airportrunway at the town of Goma, and in 2011 with continuing lava lake activity.Nyiragongo has erupted at least 34 times since 1882. The volcanic rocks ofthese and the older volcanoes fill the rift enough that the flow of rivers andpositions of lakes have changed over geologic time.

    Lake Kivu, the rift lake just south of the volcanoes, oncedrained north to Lake Edward and ultimately to the Nile River, but thevolcanism blocked the outlet and now Lake Kivu drains southward into LakeTanganyika. Local legends, recounted by Dorothy Vitaliano in her book onGeomythology, Legends of the Earth (Indiana University Press, 1973), tell thestory of demigods who lived in the various Virunga volcanoes. As demigods do,these guys had frequent arguments and battles, which are probably the folkloreequivalent of actual volcanic eruptions. The stories accurately reflect –whether through observation or happenstance – the east to west migration ofvolcanic activity in the range.

    The gases associated with the volcanic activity seep intothe waters of Lake Kivu, which has high concentrations of dissolved carbondioxide and methane. Generally the gases are contained in the deeper waterunder pressure – Lake Kivu is the world’s 18th deepest lake, at 475meters, more than 1,500 feet. But sometimes lakes experience overturns, withthe deeper waters flipping to the surface. When gases are dissolved in thewater and the pressure reduces, they can abruptly come out of solution likeopening a carbonated beverage bottle. This happened catastrophically at LakeNyos in Cameroon in 1986, asphyxiating 1700 people and thousands of cattle andother livestock. The possibility that Lake Kivu could do the same thing is areal threat to about two million people.

    The critically endangered mountain gorilla lives in theVirunga Mountains, which also holds the research institute founded by DianFossey.
    —Richard I. Gibson



  • Today’s episode focuses on one of thosewonderful jargon words geologists love to use: Ophiolites.

    It’s not a contrived term like cactolith nor some reallyobscure mineral like pararammelsbergite. Ophiolites are actually really importantto our understanding of the concept of plate tectonics and how the earth worksdynamically.

    The word goes back to 1813 in the Alps, where AlexandreBrongniart coined the word for some scaly, greenish rocks. Ophiolite is acombination of the Greek words for snake and stone, and Brongniart was also aspecialist in reptiles. So he named these rocks for their resemblance to snakeskins.

    Fast forward about 150 years, to the 1960s. Geophysical data,deep-sea sampling, and other work was leading to the understanding that theearth’s crust is fundamentally different beneath the continents and beneath theoceans—and we found that the rocks in the oceanic crust are remarkably similarto the greenish, iron- and magnesium-rich rocks that had been labeledophiolites long ago and largely ignored except by specialists ever since.

    Those rocks that form the oceanic crust include serpentineminerals, which are soft, often fibrous iron-magnesium silicates whose name is yetanother reference to their snake-like appearance.  Pillow basalts, iron-rich lava flows thatsolidify under water with bulbous, pillow-like shapes, are also typical ofoceanic crust. The term ophiolite was rejuvenated to apply to a specificsequence of rocks that forms at mid-ocean ridges, resulting in sea-floor spreadingand the movement of plates around the earth.

    The sequence usually but not always includes some of themost mantle-like minerals, such as olivine, another iron-magnesium silicate,that may settle out in a magma chamber beneath a mid-ocean ridge. Shallower, relativelynarrow feeders called dikes toward the top of the magma chamber fed lava flowson the surface – but still underwater, usually – that’s where those pillow lavassolidified. There are certainly variations, and interactions with wateras well as sediment on top of the oceanic crust can complicate things, but onthe whole that’s the package. So why not just call it oceanic crust and forgetthe jargon word ophiolite? Well, we’ve kind of done that, or at leastrestricted the word to a special case.

    Pillow Lava off Hawaii. Source: NOAA
    The word ophiolite today is usually used to refer to slicesor layers of oceanic crust that are on land, on top of continental crust. Butwait, you say, you keep saying subduction is driven by oceanic crust, which isdenser, diving down beneath continental crust, which is less dense. Well, yes –but I hope I didn’t say always.

    Sometimes the circumstances allow for some of the oceaniccrust to be pushed up over bits of continental crust, despite their greaterdensity. One area where this seems to happen with some regularity is a settingcalled back-arc basins, which are areas of extension, pulling-apart, behind thecollision zone where oceanic crust and continental crust come together with theoceanic plate mostly subducting, going down under the continental plate. Ittook some time in the evolution of our understanding of plate tectonics for theidea to come out that you can have significant pulling apart in zones that arefundamentally compression, collision, but they’re recognized in many placestoday, as well as in the geologic past.

    It seems to me that back-arc basins are more likely todevelop where the interaction is between plates or sub-plates that arerelatively weak, or small, and more susceptible to breaking. An example iswhere two oceanic plates are interacting, with perhaps only an island arcbetween them. The “battle” is a closer contest than between a big, strong continentand weaker, warmer, softer, oceanic crust, so slices of one plate of oceaniccrust may be squeezed up and onto the rocks making up the island arc. Thishappens in the southwest Pacific, where the oceanic Pacific Plate and theoceanic part of the Australian Plate are interacting, creating back-arc basinsaround Tonga and Fiji and elsewhere. It also happens where continental material is narrower, orthinner, or where the interaction is oblique or complex. One example of this todayis the back-arc basin in the Andaman Sea south of Burma, Myanmar, where theIndian Ocean plate is in contact with a narrow prong of continent, Indochinaand Malaya.

    We’ve now recognized quite a few ophiolites on land,emplaced there long ago geologically. At Gros Morne National Park inNewfoundland, the Bay of Islands ophiolite is of Cambrian to Ordovician age.The area is a UNESCO World Heritage Site for the excellent exposures of oceaniccrust there, not to mention fine scenery.

    On Cyprus, the Troodos Ophiolite represents breaking withinthe Tethys Oceanic plate as it was squeezed between Gondwana, or Africa, andthe Anatolian block of Eurasia, which is today’s Turkey. The Troodos Ophioliteis rich in copper sulfides that were probably deposited from vents on amid-ocean ridge. In fact, the name Cyprus is the origin of our word copper, byway of Latin cuprum and earlier cyprium.  

    On the island of New Caledonia, east of Australia and in themidst of the messy interactions among tectonic plates large and small, theophiolite is rich in another metal typical of deep-crust or mantle sources:nickel. There’s enough to make tiny New Caledonia tied with Canada for thirdplace as the world’s largest producer of nickel, after Indonesia and thePhilippines.

    There’s a huge ophiolite in Oman, the Semail Ophiolite,covering about a hundred thousand square kilometers. It’s one of the mostcompete examples anywhere, and it was pushed up on to the corner of the Arabiancontinental block during Cretaceous time, around 80 million years ago. Like theone in Cyprus, this one is also rich in copper as well as chromite, anotherdeep-crustal or mantle-derived mineral.

    The Coast Range Ophiolite in California is Jurassic, about170 million years old, and formed at roughly the same time as the Sierra NevadaBatholith developed as a more standard response to subduction. It’s likely thatwestern North America at that time was somewhat like the southwestern Pacifictoday, with strings of island arcs, small irregular continental blocks, anddiverse styles of interaction – the perfect setting for a long band of oceaniccrust to be pushed up and over other material. The whole thing ultimately gotamalgamated with the main North American continent. I talked a bit more about theseevents in the episode on the Franciscan, November 7, 2014.

    —Richard I. GibsonLINKS: Nice images from Oregon State Oman Virtual Field Trip 


  • In today's episode we’re going to space.Specifically, Mars. You didn’t really think that earth science is reallylimited to the earth, did you? Our topic today will be the Valles Marineris.

    The Valles Marineris is a longseries of canyons east of Olympus Mons, the largest mountain in the solarsystem. These canyons are about 4,000 km long, 200 km wide and up to 7 km(23,000 ft) deep. On terrestrial scales, the Valles Marineris is as long as thedistance from New York to Los Angeles. That’s about the same as Beijing to HongKong or Madrid to Copenhagen for our international listeners. They are as wideas central Florida, central Italy, or the middle of the Korean peninsula. Twoand a half times deeper than Death Valley, though only about 60 percent of thedepth of the Marianas Trench, the lowest point on earth.
    Valles Marineris Image Courtesy NASA/JPL-Caltech
    Not to be outdone, our planet, Earth,has even bigger valleys. These occur at the oceanic ridges, where platespreading takes place. The longest rift valley on earth lies in the middle ofthe Mid-Atlantic Ridge, and it is more than double the length of the VallesMarineris. But let’s not belittle Mars. After all, while we have a pretty goodidea for how oceanic rifts form on earth, there is quite a bit of debate abouthow Mars’ great valley formed.
    The most popular theory suggeststhat the Valles Marineris are an analog to our oceanic rifts, and formed by thesame process. As the volcanoes of the nearby Tharsis region developed, theMartian crust bowed down toward the center of the planet due to the weight ofthe new volcanic rocks. In time, the crust began to crack. This crack is what wesee in the Valles Marineris. Unlike on Earth, this rift valley did not continueexpanding, but shut down as the Tharsis Region, and Mars as a whole, cooled.Remember that unlike Earth, Mars does not have plate tectonics. It doesn’t havea continual process of hot material (like lava) rising to the surface, while relatively cold material (like the oceanic crust) is brought down towards the planet’s center.
    More recent work has usedsatellite images, and high resolution elevation data to develop new insightinto how the Valles Marineris formed. While images from the 1970’s Mariner 9orbiter were quite blurry by today’s standards, new missions in the late 90’sto early 2000’s have given us a better view of the Martian surface than we haveavailable for the earth. The Mars Reconnaissance Orbiter can take images whereeach pixel is about 0.5 m or 20 inches. That is, the color on each image is anaverage of an area of 0.25 square meters, or 2.5 square feet. It can then useimage pairs to estimate the elevation of any point on the Martian surface witha pixel size of 0.25 m, or about 10 inches.
    These new satellite imagesinclude multispectral data, or images that look at different wavelengths oflight. The camera on your phone works in the same way: There are sensors thatpick up, red light, green light, and blue light. Your phone records theintensity of each color in each part of the image, and then plays it back onyour phone’s screen to create a picture.
    Some of the satellites orbiting Marstake this to the next level. They don’t just take different slices of coloredlight, but also longer wavelength, infrared light. If you’ve ever seen an imagefrom a thermal imaging camera, you know what this is. Parts of you show up ashotter or colder on the screen. It’s the same with the surface of the earth, orMars. Scientists can compare the intensity of different wavelengths of lightfrom each point on the surface. They can then compare these values, with whatwould be expected for different rock types. In other words, we’re able toroughly determine the types of rocks on the Martian surface without eversetting a boot, or rover tread, on the red planet.
    Data from these images has shownthat the Valles Marineris have layered rock formations both on the sides of thecanyons, and within them. The great valley has seen many landslides over thelast 3.5 Billion years of its existence, as well as new and smaller canyonscarved into it. Scientists now speculate that rather than just forming as a bigcrack in the Martian surface, the Valles Marineris have been sculpted byflowing water, either in its liquid form as rivers, or in its solid form asglaciers.
    An alternative hypothesisproposes that the Valles Marineris formed as a crack during a massive, planetaryscale landslide. This landslide was about half the size of the US or China. Howdo you form a landslide that big? Well, you need a large pile of relativelyweak rock, and high elevations for the landslide to flow from.
    A key player here is salt. Saltis relatively weak as compared to rock, and can deform easier when squeezed. Itcan also hold water, which can be driven off by heating. On Earth, weak saltlayers are partly responsible for undersea landslides in the Gulf of Mexico.The Opportunity rover had found some salt layers during its mission on Mars, sowe know salt is present on the red planet.
    Some scientists interpret thelayers on the sides of the Valles Merinaris to be made of salt, and possiblyinclude pockets of ice. This would imply that those layers are weak, and couldpotentially move downhill under the right circumstances.
    Heating in the Tharsis regionhelped de-water salts under the future landslide, melted ice pockets, andcreated high elevations on one side of it. Think of it like putting a can on awet metal sheet. If you raise one side of the sheet, the can will slide to thelower side. Just like that, the salty Martian crust broke, and slid downhill.
    A crack in the side of thislandslide allowed massive amounts of underground water to escape. As the waterflowed downhill, it eroded the crack to form a massive canyon. This canyon isthe Valles Marineris. The flood that helped form the Valles Marineris wasprobably bigger than any seen on earth. Bigger than the massive glacial outburstfloods that formed the channeled scablands of the northwestern United States.Dick Gibson discussed outburst flooding in the December 27, 2014 episode. Unlike the Earth, the Martian surface has been relatively quiet sincethe Valles Marineris formed 3.5 billion years ago.
    —Petr Yakovlev

    This episode was recorded at thestudios of KBMF-LP 102.5 in beautiful and historic Butte, Montana. KBMF is alocal low-power radio station with twin missions of social justice andeducation. Listen live at butteamericaradio.org.






  • As the name implies, mud volcanoes are eruptions of mud –not molten rock as in igneous volcanoes.  They’re found all around the world,amounting to about a thousand in total number known. The one thing they have incommon is hot or at least warm water, so they occur in geothermal areasespecially, but they also are found in the Arctic.
    They range in size from tiny, just a few meters across andhigh, to big things that can cover several square miles. In Azerbaijan some mudvolcanoes reach 200 meters, 650 feet, in height, and around the world many ofthem do have conical, volcano-like shapes. But there are others that are justlow mounds, more like a shield volcano.

    A little (15-cm) mud volcano in New Zealand.
    Photo by Richard Gibson.The mud is often enough just a slurry of suspended fine-grainedsediment that mixes with the hot water. And by hot water, we don’t necessarilymean incredibly hot – mud volcano temperatures as cold as a couple degrees Centigradeare known, but most are associated with temperatures approaching the boilingpoint of water.  In some places, like Yellowstone,the water is acidic which helps it dissolve rocks down to the tiny fragments inmud, and in other places it may just be the weathered soil and debris picked upby the water that makes the mud.

    Mud volcanoes can erupt violently, or seep slowly, andemissions can last from minutes to years. I think it’s fair to think of some ofthem as geysers in which the water contains a lot of sediment, while others aremore like thick, viscous muddy warm springs.

    Besides water and fine sediment, mud volcanoes often containnatural gas – most commonly methane, but sometimes carbon dioxide, nitrogen, orother gases. The pressure of these gases is often the driving force behinderuptions, and with a hydrocarbon gas like methane present you might think mudvolcanoes would be associated with oil and gas fields, and you’d be right. Thehundreds of mud volcanoes in Azerbaijan and in the adjacent Caspian Sea are inthe midst of the first great oil province to be exploited, and some of the petroleumdeposits there are related to structures in the rocks and sediments caused bythe upward force of the mud, which can bend its confining rocks as it rises,just as a salt dome can do. And since methane is flammable, often enough thereare flames associated with mud volcanoes. In 2001, near Baku, Azerbaijan,flames shot 15 meters, near 50 feet, into the air. Gobustan in Azerbaijan is aWorld Heritage Site for its abundant rock carvings dating to 5000 to 20,000years ago or more. The flaming methane eruptions of mud volcanoes in Azerbaijanhave been linked to the development of the Zoroastrian religion, and in factthe name Azerbaijan derives from words meaning Land of the Eternal or SacredFire.

    The most destructive mud volcano eruption in recent yearswas on the island of Java, in Indonesia, in May 2006. It erupted in the middleof a rice paddy, and ultimately killed 20 people, caused nearly 3 billiondollars in damage, and displaced 60,000 people. The mud it erupted covers aboutseven square kilometers, nearly three square miles, and in 2018 it continues toerupt something like 80,000 cubic meters of mud every day – that’s almost 3million cubic feet, 32 Olympic swimming pools each day.

    What caused the violent and extensive eruption of the LusiMud Volcano, also called the Sidoarjo mud flow, on Java is not clear. It may besimply part of the ongoing natural tectonic and magmatic processes in theregion, which is dotted with many real volcanoes, the kind that carry moltenrock to the surface as lava, and there’s a fault system that may provide a conduitfor hot water from a volcano about 50 kilometers away. Lusi may be an entirelynatural phenomenon. But there are also interesting possible trigger mechanisms.One suggests that a large earthquake two days before the mud volcano eruptedchanged the plumbing system enough to spur the eruption. That’s reasonable,since we know that earthquakes can have significant effects on geyser systems.Old Faithful in Yellowstone changed its eruption period following the strong HebgenLake earthquake in 1959. The other possible trigger is nearby drilling by a gasexploration company, which may have encountered an open pocket of gas or someother feature that ultimately may have allowed enough pressure to build up tomake the mud volcano erupt. Good science on all sides of this issue have notresolved its origin with certainty, but on the whole I think the consensus isthat the mud eruption was indeed triggered by the drilling. Studies continue,and there are legal cases in progress too, of course.

    Sidoarjo Mud Flow, Indonesia, 2008NASA image created by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team. Caption by Michon Scott, based on interpretation by Geoffrey S. Plumlee, U.S. Geological Survey Crustal Imaging and Characterization Team. Source Another mud volcano that was recently in the news is inTaiwan. Taiwan has at least 17 mud volcanoes which have been known forcenturies, and the flammable natural gas associated with them was used inbrick-making in southern Taiwan. The gas is probably methane, and it sometimesignites naturally. The Wandan mud volcano in this area has a sporadic history,dormant for 9 years in the 1980s but erupting with damage in 2011 and 2016.Taiwan is on the subduction zone between the Philippine plate and Eurasia,complicated by a change in orientation of the subduction zone where Taiwansits. This complex tectonic setting, together with the heat liberated bysubduction, is probably the ultimate cause of the earthquakes, geologicallyrecent volcanism, and the mud volcanoes on Taiwan.
    Mud volcano eruptions are probably no more predictable thanreal volcanoes or earthquakes, but their similarity to geysers might give atleast an element of predictability to them. A mud volcano that erupted inTrinidad in February 2018 seems to have a period of about 25 to 30 years, butthat’s obviously a pretty wide range. The most recent event at Trinidad’sDevils Woodyard mud volcano covered an area about 100 meters across and tossedmud six meters into the air. Like the features in Azerbaijan, the mud volcanoesin Trinidad are closely associated with hydrocarbon deposits, includingTrinidad’s famous pitch lake – thick tarry oil at the surface of the land.

    Most of the hot mud activity in Yellowstone isn’t reallywhat you’d call mud volcanoes. It’s more boiling mud-rich hot springs like theFountain Paint Pots, but every now and then they can make small cones, lessthan a meter high, and in the past there have been mud-rich geyser eruptions atYellowstone.

    By some estimates there are many more mud volcanoes on thesea floor than there are on land. The known offshore mud volcanoes are oftenassociated with methane hydrates – methane gas frozen into ice in the sedimentbeneath the sea floor. So it would be no surprise that as those ice-methanecomplexes melt they might drive the development of mud volcanoes underwater.

    —Richard I. Gibson
    Links:Trinidad Taiwan 
    Indonesia 



  • Smilodon and dire wolves (drawing by Robert Horsfall, 1913)
    Running time, 1 hour. File size, 69 megabytes.

    This is an assembly of the episodes in the original seriesfrom 2014 that are about Cretaceous and Cenozoic vertebrates.

    I’ve left the references to specific dates in the podcast sothat you can, if you want, go to the specific blog post that has links andillustrations for that episode. They are all indexed on the right-hand side ofthe blog.

    Thanks for your interest and support!




  • Morganucodon, a possible early mammal from the Late Triassic. Length about four inches.Drawing by FunkMonk (Michael B. H.) used under Creative Commons license. 

    Running time, 1 hour. File size, 68 megabytes.
    This is an assembly of the episodes in the original seriesfrom 2014 that are about Triassic and Jurassic vertebrates.

    As usual, I’ve left the references to specific dates in the podcast sothat you can, if you want, go to the specific blog post that has links andillustrations for that episode. They are all indexed on the right-hand side ofthe blog.

    Thanks for your interest and support!




  • Vanadium is a metal, and by far its greatest use is in steelalloys, where tiny amounts of vanadium improve steel’s hardness, toughness, andwear resistance, especially at extreme temperatures. As I reported in my bookWhat Things Are Made Of, more than 650 tons of vanadium was alloyed with ironto make the steel in the Alaska Pipeline, and there’s no good substitute forvanadium in strong titanium alloys used in jet planes and other aerospaceapplications.

    Vanadium isn’t exactly one of the well-known elements, butin terms of abundance in the earth’s crust, most estimates indicate thatthere’s more vanadium than copper, lead, or tin. But it’s difficult to isolate,and it wasn’t produced chemically as a chloride until 1830, when Swedishchemist Nils Sefström named it for the Norse goddess of beauty, Vanadis,perhaps better known as Freyja. It wasn’t until 1867 that pure vanadium metalwas isolated by British chemist Henry Roscoe, whose work on vanadium won himthe name of the vanadium mica roscoelite.



    As a mineral collector, I’m attracted to vanadinite, leadvanadate, because it forms beautiful hexagonal crystals, often bright red andso abundant from one lead-mining area of Morocco that excellent specimens canbe had without mortgaging your house. Some vanadinite crystals are like perfectlittle hexagonal barrels, and others can form needle-like spikes around acentral crystal, making the whole thing look like a cactus with caramel-orangespines.

    Some of the vanadium for making steel alloys comes fromprimary mined vanadinite, but much more was once produced as a by-product ofphosphorous manufacture, because it’s commonly associated with phosphate rock. Andtoday, a lot of the world’s vanadium comes from refining crude oil and from flyash residues, which are products of coal combustion. I got curious about whyvanadium metal is so closely connected with these organic deposits.

    Crude oil actually has lots of trace elements in it,including metals like gold, tin, and lead, but by far the most abundant are nickeland vanadium, as much as 200 parts per million nickel and 2000 parts permillion vanadium in some crude oils, especially heavy, tarry oils like thosefound in Venezuela. In some oil, the nickel and vanadium can add up to 1% byweight of the oil, an incredibly huge amount. Refining Venezuelan crude gavethe U.S. a lot of vanadium back in the late 20th century. But why isit in there?

    Oil and coal are both the result of decaying and chemicallychanging plant matter. Forget dinosaurs; virtually all oil, natural gas, andcoal comes from plants – usually marine algae for oil and gas and more woody,land-based vegetation for coal. There’s a class of organic molecules calledporphyrins. I’m no organic chemist, but these complex hydrocarbon molecules, madeof carbon, hydrogen, oxygen, and nitrogen have boxy ring-like structures withopen space in the centers. Chlorophyll and hemoglobin are related chemicals,both of which contain metals in the middle of the structure, magnesium inchlorophyll and iron in hemoglobin. The vacant holes in the centers ofporphyrins in crude oil are ideal for trapping metal molecules, and apparentlyvanadium, in the form of a VO2 ion, is one of the easiest to trap because ofits molecular size and electronic valence.
    The vanadium comes from the original oil source rock, sothere’s quite a range in vanadium content around the world. Heavy oils, likethe tars in Venezuela, hold more than fluid oils like those in Saudi Arabia.This has more or less been known since at least the 1920s, and today thevanadium and other metal contents of oils are being used to characterize theoriginal source rocks even when those source rocks no longer exist or are nolonger what they once were.

    The United States has had no mine production of vanadium since2013 and even then we were 94% dependent on imports. Today 100% of our vanadiumis imported, and we also produce some vanadium from imported crude oil and ash.More than 90% of the world’s vanadium is mined in China, Russia, and SouthAfrica, although the US imports much of what it needs from the Czech Republicand Canada as well as Russia. We also imported enough ash and refining residuesto account for 9000 tons of vanadium in 2015, mostly going as I said to makingsteel alloys. A new emerging use is in high-capacity storage batteries, wherevanadium compounds make the electrolyte. These batteries have potential usesfor renewable energies such as wind and solar power, and although in 2015 and2016 several companies were working on prototype designs, they’re still prettyexpensive batteries.

    Way back in 1971 when I was a teaching assistant for theIndiana University Geologic Field Station, on one mapping project we went tothe Mayflower gold mine south of Whitehall, Montana. I collected a bunch ofrocks with interesting looking sparkly crystals – some of which I’ve onlyrecently gotten around to really studying. I gave a talk at the 2017 MontanaBureau of Mines and Geology Mineral Symposium on minerals from there thatturned out to be vanadium-bearing, including vanadinite, although it’s probablyan arsenic-rich variety, and stranger minerals like descloizite, a lead-zincvanadate, tangeite, calcium-copper vanadate, and some others. I even thinkthere are some tiny bits of roscoelite, the vanadium mica named for the chemistwho first prepared vanadium metal.  

    Even more exciting for me are some tiny, millimeter-sizedred-orange crystals in the specimens I found at the Mayflower Mine. All I knewfor a long time was that I couldn’t figure out what they were. By looking attheir crystal shapes and properties, I narrowed it down to two very strange andvery rare minerals – gottlobite, a calcium-magnesium vanadate, and calderónite, a lead-iron vanadate. Bothof these minerals are so obscure I didn’t really seriously imagine I hadactually collected one of them. But, thanks to an analysis by Stan Korzeb, theeconomic geologist at the Montana Bureau of Mines and Geology, it turned outthat I did indeed find calderónite,32 years before it was described as a new mineral in 2003. Stan’s analysis inJanuary 2018 used EDX, or energy-dispersive x-ray spectroscopy, a techniquethat gives not only the elements present in a mineral, but their relativeproportions, which allowed Stan to calculate the chemical formula. The lead-ironvanadate calderónite he found is intergrown withdescloizite, a lead-zinc vanadate. This probably indicates changing iron-zincconcentrations in the fluids that precipitated the minerals. This represents justthe 11th documented calderóniteoccurrence in the United States and the second in Montana. Stan identified thefirst in Montana in the fall of 2017.

    It’s an obscure mineral, and the crystals are tiny, but itmade this mineral collector’s day.

    —Richard I. Gibson
    Link:USGS Mineral Commodities - Vanadium (PDF) 


  • You may have seen some of the spectacular images of theearth in southern Algeria, curves and colors like some Picasso in the oppositeof his cubist period. If you haven’t, check out the one from NASA, below. 
    The ovals and swirls, with their concentric bands, areimmediately obvious to a geologist as patterns of folds, but not just linearfolds like many anticlines and synclines form. These closed ovals representdomes and basins – imagine a large scale warping, both up and down, in a thicksuccession of diverse sedimentary rocks, like sets of nested bowls, some ofthem right-side up and some inverted, then all sliced off halfway through.

    But “obvious to a geologist” has plenty of limitations in aspace image. Without knowing more information, it’s difficult to be sure if anoval is a basin or a dome. And you can speculate, but without some groundtruth, it’s challenging to be sure what the rock types are.

    Ahnet-Mouydir, Hoggar Mountains, Algeria. NASA image - source
    This area, called the Ahnet-Mouydir, on the flank of the HoggarMountains close to the middle of the Sahara Desert, is remote, inhospitable,and arid, and called the “land of terror” for a reason. The rocks represent athick sequence of marine sandstones, shales, and limestones, spanning a hugerange of ages, from at least the Ordovician to the early Carboniferous – 150million years or more, a great chunk of the Paleozoic era.

    The core of the Hoggar Mountains is an old Precambrianblock, not as big as the cratons and shields that form the hearts of most ofthe continents, but otherwise similar. It might have been something like amicrocontinent that became amalgamated into the growing supercontinent ofGondwana about 600 million years ago. After that amalgamation, seas came andwent much like they did in western North America throughout much of thePaleozoic era, laying down the sediments that became the rocks we see today inthe northern Hoggar Mountains.

    That’s all well and good – but here’s the next question, howdid the rocks get deformed into these oval domes and basins? If you imagine thekinds of collisions that are typical on earth, you think of linear orcurvilinear things – island arcs, edges of continents and such – that when theycollide, are likely to make linear belts of deformation. This is why so manymountain ranges are long, linear features, and the folds and faults that makethem up also tend to be linear. Domes and basins happen, but that seems to bealmost all we have here in these mountains.

    We have to look for a deformational event that is later thanthe youngest rocks deformed. So if some of these rocks are as young as earlyCarboniferous, about 340 million years old, the mountain-building event thatfills the bill is the Hercynian Orogeny, where ‘orogeny’ just meansmountain-building.

    The Hercynian, at about 350 to 280 million years ago,represents the complex collision between Gondwana and the combined NorthAmerica and Europe, which were already more or less attached to each other. Theleading edge of Gondwana that collided was in what is now North and WestAfrica, and the collision produced mountain ranges all over – the Allegheniesin the central Appalachians in North America, and a complex swath of mountainsacross central Europe, from Spain, across France to northern Germany and intoPoland, as well as elsewhere. In Africa, the most intense squeezing was at theleading edge, in what is now Morocco and Mauritania, colliding with NorthAmerica, and northern Algeria, impacting Iberia.

    The basins and domes of southern Algeria that we’re tryingto understand are 1500 kilometers or more from that leading edge of continentalcollision. So I think – and full disclosure, I’ve never really researched thisarea in detail – that what must have happened is that that distant hinterlandwasn’t pushed into tight, linear belts like those we find along the lines ofcollision, but the force was enough to warp the sediments into these relativelysmall domes and basins. Alternatively, it might be possible that the brittlePrecambrian rocks beneath the sedimentary layers broke from the force of thecollision, so that the sedimentary layers draped over the deeper brittlesurface like a carpet lying over a jumble of toy building blocks – some high,some low.

    The latter idea, that the brittle basement rocks were brokenand pushed upward with the sedimentary layers draped over them is supported byresearch published in the journal Terra Nova in 2001. Hamid Haddoum andcolleagues studied the orientations of folds and faults in this area, trying tofigure out the orientations of the stresses that caused them. Their data show ashortening direction – which means compression, or squeezing – during earlyPermian time oriented about northeast-southwest. That is consistent with thecollision that was happening at that same time between what is now Senegal andMauritania, in westernmost Africa, and the Virginia-Carolinas region of what isnow the United States. Haddoum and his colleagues show cross-sections withbasement upthrusts, basically high-angle reverse faults where older rocks aresqueezed so much that they are pushed up and over younger rocks. This is quitesimilar to the Laramide Orogeny in the western United States about 80 to 50million years ago, but this compression was happening about 280 million yearsago as the supercontinent of Pangaea was assembled during the early PermianPeriod. Both represent deformation at relatively great distances from the linesof continental collision. In the case of the Laramide in western United States,one idea for transmitting the stress so far from the collision is that thesubducting slab of oceanic crust began to go down at a relatively gentle angle,even close to horizontal, creating friction and stress further away from thesubduction zone than normal. Whether that’s the case here in southern Algeriaisn’t clear for this Hercynian collision.

    I wouldn’t think of this area as high mountains, such asthose that must have formed along the lines of Hercynian collision. Maybe morelike warped, uplifted plateaus – but whatever they were, they were certainlysubject to erosion. Erosion probably wore the domes and basins down to a commonlevel, so that the nested bowls were exposed in horizontal cross-section –which for geologists is the equivalent of a geologic map. And that’s what thebeautiful photos reveal.

    The area might have been planed off even more by Permian glaciersduring and after the Hercynian mountain-building events. But then, during theMesozoic era, seas returned to the region and all this mess of eroded domes andbasins was buried beneath even more sediments. Sometime relatively recently,during the Cenozoic era, the past 65 million years, everything was uplifted atleast gently, so that the highest parts – including today’s Hoggar Mountains,were stripped of the younger Mesozoic sedimentary rocks, revealing the mucholder Paleozoic rocks in the domes and basins.


    —Richard I. Gibson
    Link: Haddoum, H., Guiraud, R. and Moussine-Pouchkine, A. (2001),Hercynian compressional deformations of the Ahnet–Mouydir Basin, AlgerianSaharan Platform: far-field stress effects of the Late Palaeozoic orogeny.Terra Nova, 13: 220–226. doi:10.1046/j.1365-3121.2001.00344.x




  • It isn’t true that all geologists drink beer. But many do,and I’m one of them. Today I’m going to talk about theintimate connection between geology and beer.

    Beer is mostly water, and water chemistry has everything todo with beer styles. And water chemistry itself depends mostly on the kinds ofrocks through which the water flows. You know about hard and soft water – hardwater has more dissolved chemicals like calcium and magnesium in it, and whilesalts of those chemicals can precipitate out of hard water, making a scum onyour dishes, they also can be beneficial to development of bones and teeth. Inthe United States, the Midwest and Great Plains have some of the hardest waterbecause of the abundant limestones there, and in Great Britain, southern andeastern England have harder water than Scotland for similar reasons.

    But it wasn’t limestone that made Burton-upon-Trent a centerof brewing in the 19th Century, when it was home to more than 30breweries. The water there is rich in sulfate which comes from gypsum, calciumsulfate, in the sandstone underlying the region. Those sandstones are Permianand Triassic in age, representing a time when much of the earth was arid. Thosedry conditions allowed gypsum to crystallize in the sediments. Gypsum is muchmore soluble than limestone, and the slightly acidic waters of Burton help withthat. Burton water has ten times the calcium, three times the bicarbonate, and14 times the sulfate of Coors’ “Rocky Mountain Spring water” in Colorado. That certainlymakes Coors’ Burton brewery product rather different from that made inColorado.

    In fact, the addition of gypsum to beer is called“Burtonization.” This increases the hops flavor, but more important to history,sulfates act as preservatives in beer, enough so that Burton brews of pale alescould survive the long trip to British India, giving us the India Pale Alestyle of beer. Not from India, but brewed with sulfates derived from gypsum inBritain’s rocks.

    That slight acidity in Burton’s water depends on the calciumand magnesium content, and also lends itself to extracting sugars from malted barleyin the mashing process. Calcium and magnesium also help yeast to work itsmagic. Today, home brewers can buy “Burton Water Salts” to imitate the productfrom England.

    Truman, Hanbury, Buxton & Co., Black Eagle brewery, Derby Street, Burton-upon-Trent, in 1876,
    from University of LondonLess hoppy beers often originated in areas where the sulfatecontent of the water was low. Pilsen in the Czech Republic, home to pilsnerbeer, has almost no sulfate and only 7 parts per million calcium in its water,compared to around 300 for Burton. Pilsen is in an area of metamorphic rocksthat don’t yield the typical hard-water-making elements.

    The presence of Carboniferous age limestones in Ireland makewaters that are high in calcium and carbonate, but they lack the sulfate ofnorthern England. Together with other differences, that makes the area aroundDublin ideal for making a stout porter known today as Guinness.

    After water, it’s the soil that makes the most difference tobeer. Hops can grow in a wide range of soils, even the decomposed granite wehave here in Butte, but the thick, well-drained soils of Washington and Oregon,weathered from volcanic rocks, make those states the source of 70% of the hopsgrown in the United States.

    The surge of craft breweries in the United States has givenrise to some interesting geological names for brews. Great Basin Brewing inReno and Sparks, Nevada, has Ichthyosaur IPA, known as Icky, as well asOrogenesis, a Belgian-style amber ale. Socorro Springs, in New Mexico, brewsIsopod Pale Ale and Obsidian Stout is available from Deschutes in Oregon.  You can get Triceratops Double IPA at NinkasiBrewing in Eugene, Oregon, and Pangaea Ale at Dogfish Head in Delaware. Andeven though it’s more chemical than geological, we shouldn’t leave out AtomicAle’s Dysprosium Dunkelweizen, made in Richland, Washington. Dysprosium is arare-earth element found in the phosphate mineral xenotime and other strangerminerals.

    San Andreas Brewing Company, near the fault in California, boastsOktoberquake and Aftershock Wheat.

    And I’m undoubtedly prejudiced, because I’m the HouseGeologist at Quarry Brewing here in Butte, which probably has the best mineralcollection in a brewery in the United States, but I think their collection ofgeological names for their beers is unexcelled: Shale Pale Ale, Galena Gold,Open Cab Copper, and Gneiss IPA, and seasonals including Albite, Basalt,Bauxite, Calcite, Epidote, Halite, Ironstone, Porphyry, Opal Oktoberfest,Schist Sour, Rhyolite Rye Pale Ale, Pyrite Pilsner, and more. Mia the bartenderand I tried to come up with a fitting name for a 50-50 mix of basalt andgneiss. I wanted it to be charnockite, but we ended up calling it Mia’sMixture.

    Next time you enjoy a beer, thank geology!

    —Richard I. Gibson More Geology of Beer 
    And another from Lisa Rossbacher
    Image: Truman, Hanbury, Buxton & Co., Black Eagle brewery,Derby Street, Burton-upon-Trent, in 1876 from University of London


  • Ganoid fish from an old textbook (public domain)Running time, 1 hour. File size, 70 megabytes.


    This is an assembly of the 15 episodes in the originalseries from 2014 that are about Paleozoic vertebrates.

    I’ve left the references to specific dates in the podcast sothat you can, if you want, go to the specific blog post that has links andillustrations for that episode. They are all indexed on the right-hand side ofthe blog.
    Thanks for your interest and support!