Book month continues...

Over the Snowpocalypse, I read Bob Hazen's book Genesis: the Scientific Quest for Life's Origin. Hazen is a celebrated and charismatic scientist whose primary gig is at the Carnegie Institution of Washington, though he is also the Clarence Robinson professor of geology at George Mason University. (He's also the guy who got some time in the spotlight the year before last with his ideas about mineral evolution and one of the team manning the Carnegie's new initiative the Deep Carbon Observatory.)

The book is an insider's account of what insights science has gained into how life began on our planet. Spanning several decades and labs on three continents, the story is ultimately one of chemistry, and of people. The chemistry is the knowledge part of it: how did life's fundamentals (metabolism and genetics) come to be? We know a lot about how to put together polymers from smaller (and presumably abundant) monomers, and we know a lot about the rawest forms of both metabolism and the passing on of genetic information. But there is a gap, progressively narrowing through dogged science, which we don't understand. The book is very much about famililarlizing the lay-reader with the details, and limits, of our understanding.

It is also very much a book about scientists, the people who get science done. This is probably the more interesting part, at least to me. Some of the stories Hazen tells are insightful and endearing, as you get to observe major breakthroughs through the biographies of those who made them happen. There are also bizarre twists, like a debate between Bill Shopf and Martin Brazier in 20002 about the ALH 84001 meteorite, the one purported to hold fossilized Martian microbes. I'll leave the details for the reader to discover, but it sounds like a very uncomfortable scene. Also on the 'people' angle, I found it interesting to hear when Hazen was pursuing an interesting new angle, and was asked politely to stop by a colleague because the colleague had promised someone else the chance to test that particular hypothesis. Navigating the politics of research is something I don't have a lot of experience in, and so I found this intriguing. Similarly, the story of Nick Platts and the PAH World hypothesis was a neat case study in how science can work -- albeit more dramatic and "Eureka!"-ish than the usual lab monotony. Finally, I really enjoyed the flavor provided by Hazen's anecdotes about life around the Carnegie: beers, volleyball, crowded lab space, small stories about the people who I see at GSW.

Hazen's own contributions to the field are mainly centered on the high-pressure, high-temperature lab experiements he does in the "bomb" at the Carnegie, and his expertise on minerals as a geologist. He does element mapping of fossils, and experiments to see if mineral surface chirality can 'select' for 'left-handed' or 'right-handed' amino acids. This is definitely not the centerpiece of the book though: to his credit, Hazen shows himself to be but one scientist in an active, vibrant field. His contributions are presented with equal weight as compared to his peers' and colleagues' contributions. I think it's well balanced that way. He also pulls no punches when it comes to odd, demeaning, or outright political behavior on the part of his peers, and I can imagine that some of them would have issues with the book on that count. It seems to me that he tells it like it is. Reviews on Amazon are mixed, but mostly positive, with the main criticism apparently that this is a personal account of how the science is getting done, and not a textbook. To which I would say: if you expect a personal account, then you won't be disappointed.

Overall, I would give it 4 out of 5 possible stars.

Labels: books, CO2, dc, evolution, geologists, minerals, origins of life

One of the interesting things I learned about when reading Marcia Bjornerud's Reading the Rocks was about the putting-together of our solar system. The scientific consensus is that our Sun is a second- or third-generation star, with previous iterations having been destroyed through supernovae. (The energy of the supernova is capable of fusing low-atomic-weight elements together into heavier elements.) Post-supernova, a big dispersed cloud of dust and gas existed: the pre-solar nebula. The next phase of history took the nebula and condensed it into a protoplanetary disc, and then that fried-egg-shaped accumulation self-organized (first via static charges attracting particles together -- the dust bunny effect -- and then via gravity). These simple forces brought many small particles of mass together into a smaller number of larger accumulations of mass. For a modern analogue to this process, consider the asteroid 25143 Itokawa, which looks like this:



It is, essentially, a big three-dimensional pile of space rock. I imagine that if you went and kicked it, some boulders would go flying off in all directions. It's a great example of the sorts of objects that we interpret occupying the early solar system. This process is self-amplifying (a positive feedback loop): the more mass you concentrate in a given area, the more gravity it exerts on surrounding masses, which pull towards one another, resulting in more mass, more gravity, more mass, and so on until you have planets. Eventually, if you get a big enough pile of space rock, gravity can condense it, and through warming (via radioactive decay, and potentially frictional heat from continuing impacts), the component elements could self-sort by density. Those with the highest specific gravity could sink down lower, whereas the scummier varieties would "float" up to a higher level.

Bjornerud astutely mentions that this early solar system would have lots of these little planetismals, kind of like those encountered in Antoine de Saint-Exupery's charming book The Little Prince:



Judging from the steam plume from that knee-high volcano, there's clearly some differentiation taking place down below. Now we get to the interesting part. Some asteroids fall to the planet Earth, whereupon we stop calling them asteroids, and start calling them meteorites. These meteorites are examined in great detail for information about our solar system's pre-pubescent years. One of them, the Allende meteorite, fell in the Chihuahua region of Mexico in early 1969:


image from Wikimedia commons

Geochemical analysis of the Allende meteorite by Lee, et al. (1976) showed something weird: the mineral anorthite, a feldspar, had mostly the same elements that anorthite has on Earth (or the moon): aluminum, calcium, silicon, and oxygen. But it also had a decent amount of magnesium. That's odd, because magnesium doesn't fit into anorthite's crystal structure very well at all. What's more, the magnesium in the Allende anorthite was all magnesium-26, not the "usual" magnesium-24. So... What's up with that?

It turns out that you can produce magnesium-26 as the stable daughter product when you break down radioactive aluminum-26. But aluminum-26 has a really short half-life (geologically speaking): only 730,000 years. As Bjornerud puts it, "The fact that a significant amount of aluminum-26 entered the meteorite's anorthite before decaying to magnesium-26 means that fewer than ten half-lives, and probably just a few million years, had passed between the supernova and the time that the anorthite crystals were being smelted out in the new solar refinery."

So that's stunning: the radioactive aluminum-26 was produced through a supernova explosion, and then, less than 5 million years later, a protoplanetary disc had formed and meteorites like Allende were being formed. Wow -- Until I read this passage, I had no idea that this phase of history went by so quickly! 5 million years is not a lot of time when you're talking about events of this magnitude. I was shocked, and I wanted to share this insight here. Are you shocked too?

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References:
Lee, T., D. A. Papanastassiou, and G. J. Wasserburg (1976), Demonstration of 26 Mg excess in Allende and evidence for 26 Al, Geophysical Research Letters, 3(1), 41-44.

Zimmer, Ernst (2002), Using Aluminum-26 as a Clock for Early Solar System Events, Planetary Science Research Discoveries (website). Downloaded on December 16, 2009.

Labels: analogies, astronomy, books, isotopes, meteors, minerals, planetary geology

People. It's T. rex, not "T-Rex."

Also, silicon is an element (Si); silicone is a colloidal gel made with lots of water; silica is a compound (SiO2) which is the building block of many minerals.

Unique means "one of a kind." Therefore, applying modifiers to unique, like "very unique," or "most unique," add words without adding any additional meaning. If it's unique, it's unique. There's no such thing as "very one of a kind."

Thank you for your attention.

While I'm dispensing some advice, can someone give me some...? What's the difference in meaning between geologic and geological? And similarly, historic vs. historical?

What's the difference between silicic and siliceous?

Words' worth I

Labels: dinosaurs, minerals, words

FYI, locals:
18th Annual NVMC Gem, Mineral & Fossil Show at GMU in Fairfax
November 21 2009 - November 22 2009
Saturday 10:00 AM - 6:00 PM, Sunday 10:00 AM - 4:00 PM

Labels: meetings, minerals

Galena (PbS) makes a brief appearance in the trailer for James Cameron's new movie Avatar:

That metallic luster, that cubic cleavage, that high-specific-gravity heft... It couldn't be anything else. Apparently it's more valuable in the future that it is today. I wonder if the future humans want it for the sulfur or the lead? Watch the full trailer here.

Labels: minerals, movies

As an analogy for how most minerals never get to attain their full habit (hemmed in by surrounding space constraints), perhaps even better than the boxy watermelons I mentioned last December are Buddha-shaped pears!

Labels: analogies, humor, minerals

On our hike to Grinnell Glacier this past July in Glacier National Park, I found lots of cool cobbles of float, mainly of the Mesoproterozoic metasedimentary rocks that make up the bulk of the park: the Belt Supergroup. One of these formations, the Helena Formation, is intruded by a diorite sill known as the Purcell Sill. It's a prominent rock unit showing up as a black stripe within the lighter-colored Helena Formation, exposed high on the glaciated walls throughout the park. Occasionally, you'll find pieces of it as float, and I noticed that the higher we climbed up, the more of it we saw. Here's one of my favorites among these pieces of the Purcell Sill:


This cobble shows beautiful slickenlines, small gouges into the rock as neighboring rock ground across its surface, along a fault. These physical gouges are decorated with a chemical accoutrement: the metamorphic* mineral epidote, which is a gorgeous grassy green.

Labels: faults, igneous, metamorphism, minerals, montana, national parks, proterozoic, structure

Parts 1, 2, & 3 of this series are at these links.

Today and tomorrow, I'll share some of the gorgeous Archean rocks that are exposed in Hanging Canyon, Grand Teton National Park, Wyoming. Today: the igneous stuff. Tomorrow: the structural stuff.

There were many pegmatite dikes that we saw along the hike. Here's a lovely one cutting across the metamorphic host rock:


A close up of some big muscovite "books" in the pegmatite:


A couple of parallel pegmatite dikes cutting across granite:


Here's the largest single feldspar crystal I've ever seen in the wild. The crystal starts to the left of my boot and continues for over a foot to the left of that. Its color varies between bluish gray and whitish. Where the left-most and most prominent blue stripe is, that's the edge of this monster megacryst:


Huh... Only four "igneous" photos... I guess I'll make up for that with tomorrow's structural geology post about Hanging Canyon... I have about forty photos of folds and boudins and what-not to share...

Labels: archean, granite, igneous, minerals, national parks, nova, structure, travel, wyoming

Here's two pictures of quartz I took with my new toy, a Nikon camera/microscope/digital-picture-stitcher-togetherer. More to come, clearly. Click on each image to make it bigger.

Conchoidal fractures at the tip of a quartz crystal:

Blue quartz, a distinctive mineral that's found in Virginia's Blue Ridge province:

The blue color is apparently from inclusions of ilmenite and rutile...

Purty, huh? No sense of scale, though. Tough!

Labels: blue ridge, minerals, weathering

This is another photo from Saturday's hike. Unakite is rumored to be the 'state rock' of Virginia, though it's not in the state code. Regardless of its official status, it sure is a distinctive sight: An epidotized granitoid, unakite is identified by the distinctive pairing of pistachio-green epidote and pink potassium feldspar. There's some grey/purple quartz there too. In the mid-Atlantic states, it's only found in the Blue Ridge geologic province. Here, on the trail below Dark Hollow Falls in Shenandoah National Park, my friends and I encountered this lovely boulder of unakite bearing a vein of milky quartz.

The original granitoid was Grenvillian in age, about 1.1 billion years old. Presumably the metamorphism took place during Alleghanian mountain-building, between 300-250 million years ago. Unakite has been quarried in Virginia for use as a building stone, and can be seen as tiles on the first terrace of the steps leading from the National Mall up to the southern doors of the Smithsonian's National Museum of Natural History in Washington, DC.

Labels: blue ridge, dc, igneous, metamorphism, minerals, museums, smithsonian, virginia

Some of the photos featured in my post on Green Sands Beach in Hawai'i have been added to "Hawaii Wow," a website that features intersting information about Hawai'i.

Labels: hawaii, minerals, sediment, travel

Yesterday, I took a little tour out along old Route 55 through West Virginia, the road that was replaced by new Route 55, also a source of cool outcrops. My host was Maitland S., a retired gentleman who occasionally takes geology classes at NOVA. We saw a bunch of cool stuff out there, and I'll share it all with you.

First, check out these lovely pyrolusite dendrites:





Pyrolusite is MnO2, and often grows in these beautiful branching forms. It's totally an inorganic process, but the visual similarity to botanical branching makes pyrolusite dendrites a particularly insidious form of pseudofossil. Here, it's growing on limestone, presumably the Devonian Helderberg Group -- though I'll have to check on that to be sure.

Labels: field trips, fossils, minerals, valley and ridge

I've been meaning to go check out the Soapstone Valley for years, but finally got around to it on Memorial Day. The park is a valley that shoots off to the east from Rock Creek Park, with an eastern terminus at Connecticut Avenue:



I didn't have far to walk before I found my first cobble of soapstone. It felt soapy in my hand, and was easily scratched by my fingernail. (Fingernail = 2.5 on the Mohs scale of hardness; talc = 1) I found it interesting that the soapstone cobbles had less algae growing on them than the other cobbles in the stream... Hmm. Because they slough off their outer layers more easily? Or because there's something chemical going on that prevents algae growth?


Why does anyone care about soapstone? Well, people who care about prehistory are interested in soapstone because it was easily carved to make various artifacts. As a geologist, I'm more interested in it because it's a metamorphic rock that implies an ultramafic protolith. In other words, as the various rocks that would become DC's bedrock were squished and squeezed and heated during Taconian mountain-building, one of the ingredients in the mix may have been a peridotite. As the graywacke around it metamorphosed to metagraywacke, the putative peridotite metamorphosed into soapstone.

The stuff I found in Soapstone Valley is a talc schist with porphyroblasts or relict phenocrysts of something dark and chunky in it:


Here's a close-up. The big crystals were dark green, like augite, but they had a texture that looked more like hornblende. Not sure as to their identity. I'll put one under the microscope later to try and suss out the relationship between the cleavage planes.


They're definitely mafic though! Here's an example where the large crystals are rusted out:


So there was plenty of soapstone float, but no bedrock outcrops. At first, I was in the highly foliated metagraywacke schist of the Rock Creek Shear Zone...


...but as I headed upstream I found boulders of the Kensington Tonalite, implying exposures of the KT further up the valley...


... and sure enough, that's what I found. This is the Kensington Tonalite, a late Ordovician granitoid.


Where I first crossed the contact, I thought it looked a little odd, and then a later look at the geologic map of the Washington West quadrangle (Fleming, et al., 1995):

Fleming, et al., list it as a sheared biotite tonalite of the Georgetown Intrusive Suite, which I guess explains its appearance as distinct from the Kensington Tonalite.

When I got up to the eastern edge of the park, I saw the source of the stream:


The valley widens out here, almost as if the rock is weaker... And where concrete has been poured (to stabilize the slope??) the underlying rock is etched away: it's the super-soft soapstone...


Here's a boulder of soapstone (my fingernail scratches it to demonstrate that it's soft):


Here's the geologic map of the area. You can see Soapstone Valley cutting an east-west swath across the strike of the structures. ("ss" means "soapstone"...)

My annotations on Tony Fleming's map (reference below).

Reference:
Geologic map of the Washington west quadrangle, District of Columbia, Montgomery and Prince Georges Counties, Maryland, and Arlington and Fairfax Counties, Virginia. Anthony H. Fleming, Lucy McCartan, and Avery Ala Drake. U.S. Geological Survey (Reston, VA), 1995.
_________________________________________________________________

A quick tangent to note a milestone: this is my 700^th post on NOVA Geoblog. Thanks to everyone for reading. Looking forward to 700 more...

Labels: appalachians, dc, granite, igneous, metamorphism, minerals, ordovician, piedmont

Last Saturday was my Field Studies in Geology trip to Shenandoah National Park. Here's a few shots from the day's geologizing...

Garnets in the Pedlar Formation granite gneiss, oldest rock in the park at ~1.1 Ga.


Meta-basalt columns of the Catoctin Formation (photo by Mathina Calliope):


At the end of the trip, I have the students order a series of strips of paper with different geologic events in the park's long geologic history. They have to figure out the proper order based on what they learned that day:





Lastly, a group photo overlooking the Browntown Valley:

Labels: field trips, metamorphism, minerals, national parks, nova, shenandoah, teaching

After seeing the feldspar megacrysts in Maryland's Ellicott City Granodiorite two days ago, I wanted to share some even more impressive megacrysts, those found on the periphery of the Cathedral Peak Granodiorite pluton ['CPGD'] in California's Sierra Nevada mountains.

Here's a typical look at the CPGD close to its contact with metasedimentary & metavolcanic host rocks. It's chock-full of 3-7 cm crystals of potassium feldspar, set in a more typical-looking granodioritic matrix of sub-0.5 cm crystals:

This is a nice example of an intrusive porphyry. Not all porphyritic textures result from two phase cooling: The way the story usually goes is that the magma starting underground at a realtively slow rate, then the magma (solid crystals + remaining liquid) gets tapped and erupts, with the rest cooling at a faster rate on the surface. This one clearly shows a phaneritic (coarse-grained) texture throughout; it's just that some crystals grew bigger than others. I'm not an igneous petrologist, so I won't claim to understand why. Enlighten me if you know.

Here is a close-up of one feldspar crystal shows lines of mafic inclusions (earlier-crystallizing minerals like amphibole which were caught up in the advancing front of feldspar crystallization, and trapped in the larger feldspar crystal):

My mind wants to see this as a spiral pattern, like a snowball garnet, and hence to interpret this as a feldspar crystal rotating as it grew, but that's surely wishful thinking. Especially seeing as how there's no foliation to get wrapped up in the 'rotating' porphyroblast. But... I've never seen another igneous crystal that shows this same pattern. Anyone else? Trick of the light?

Now here's something really wild:

Recall that when I took these photographs in 2003, I was out in the Sierras looking at the Sierra Crest Shear Zone, a 1-2 kilometer wide zone of smooshed rocks adjacent to the eastern boundary of the Sierra Nevada Batholith. So mainly I was interested in these older "host rocks" which were metavolcanic and metasedimentary, but I was also interested in how they related to the batholith as a whole. In places, I could see clear evidence that the plutons of the batholith were sheared, too, and in other places they appeared to have intruded post-deformation. This photo shows that the Cathedral Peak Granodiorite came along after the bulk of the deformation had happened.

How do we know? (1) It's not especially foliated itself. (2) Here, magma oozed between the foliation layers in the metasedimentary rocks immediately adjacent to the pluton. These layers flexed to allow the magma to intrude; I think of curtains billowing underwater. Then, as the pluton inflated (or as regional deformation continued to squeeze these rocks; or both), a compressive stress was exerted on these mingled layers of foliated rocks and magma. The liquid magma squished out of the way, but the solid megacrysts were trapped, and the foliation flexed and wrapped around them.

Twisted food analogy: Say I make a peanut butter and raisin sandwich. (Seriously, they're good!) I have a piece of bread, and I smear it with a mix of creamy peanut butter and chunky raisins (the giant ones from Trader Joe's). I place another piece of bread on top. Then, because I value my geology more than my manners, I lean over like I'm going to perform CPR, and exert pressure perpendicular to the plane of the bread. The peanut butter, being ductile, squishes out the sides, while the raisins are trapped, and the bread deforms around them.

Such, such are the thoughts of the hungry field geologist...

Labels: analogies, california, granite, metamorphism, minerals, primary structures

The other day I mentioned the Setters Schist.

Here's a couple of cobbles of the same formation, but lower stratigraphically than the stuff we saw on the University of Maryland petrology trip. The basal Setters has beautiful metamorphic tourmalines lying willy-nilly within the plane of foliation:







According to Mindat.org, "the general formula for this group may be written:

• A = Ca, Na, K, or is vacant (large cations);
• D = Al, Fe²⁺, Fe³⁺, Li⁺¹, Mg²⁺, Mn²⁺ (intermediate to small cations - in valence balancing combinations when the A site is vacant);
• G = Al³⁺, Cr³⁺, Fe³⁺, V³⁺ (small cations);
• T = Si (and sometimes minor Al³⁺, B³⁺);
• Y = O and/or OH; and
• Z = F, O and/or OH."

Note the constant there: boron! ...A lot of boron! Three boron atoms per unit cell... These metamorphic rocks have a sedimentary protolith. Where did the pre-metamorphic sediments get all that boron from?

Any ideas?

Labels: geology, maryland, metamorphism, minerals, piedmont

My student Joel recently went up to Clarion County, Pennsylvania, where he encountered this striking example of a stream contaminated with acid mine drainage (lifeless rust-filled stream at right) merging with an undegraded stream (at left). Wow:

Photograph by Joel Bosch.

Labels: environmental, minerals, mining, pennsylvania, water resources

After we had collectively collected a hundred pounds of samples from Mineral Hill, the final stop on the University of Maryland petrology trip was in scenic Ellicott City, Maryland, where we visited the Ellicott City Granodiorite (map to outcrops).

Like everything else on this trip, the ECGD is intimately tied in with the Taconian Orogeny (late Ordovician; caused by the collision of ancestral North America with a volcanic island arc in the Iapetus Ocean basin). However, unlike the Port Deposit Tonalite we looked at early in the trip, this one crystalized from magma at 435 +/- 15 Ma (U/Pb in zircon). It is not only much younger than the PDT, but it's also pretty young even for the Taconian Orogeny, which reached its peak around 460 Ma.

It's more potassic than the Port Deposit Tonalite, as these K-spar 'megacrysts' show:


This potassium feldspar 'megacryst' shows internal growth laminations, as small mafic bits got caught up in the growing feldspar crystal, which consumed and included them:

Not only does this help us see how the feldspar crystal's habit is a reflection of its internal structure, but it's also an example of the principle of relative dating by inclusions, expressed in a single mineral crystal! Pretty cool.

As with the PDT, xenoliths may be seen in the ECGD:


Parts of it are equigranular, and parts of it are highly foliated:


And of course my eye is always drawn to the structures, like these small faults offsetting dikes of granite which cross-cut the ECGD:




The real prize with the Ellicott City Granodiorite is to view first-hand the magmatic epidote it bears:


Most epidote is metamorphic. However, as Zen and Hammerstrom (1984) showed that epidote could also crystalize from a late-phase magma as the melt interacted with hornblende at high pressures (8 kbar; roughly 30 km depth). You'll note in the photo above the intimate association between the epidote and the hornblende. (I'm not super-confident on my titanite identification, by the way; this rock also bears similar-looking allanite. Please correct me if I'm clearly wrong.) E-an Zen has guest-posted to this blog before, and once upon a time he tasked me with searching for magmatic epidote near Haines, Alaska, in 2006. I didn't find any, but it did pique my interest. So it felt good to be able to finally see some of this rare beast. I was surprised to find it locally, considering the the original magmatic epidote paper referred mainly to west coast plutons from California to Alaska. I was also suprised because of the tremendous depth of crystallization it implied: 30 kilometers down? Wild! I collected a sample for the NOVA lab.

Thanks again to Rich Walker and Roberta Rudnick for graciously hosting me on this trip. I learned a lot, and I'm greatful for the opportunity to expand my local outcrop knowledge.

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Reference:
E-an Zen and Jane M. Hammarstrom (1984). "Magmatic epidote and its petrologic significance." Geology, September 1984. Volume 12, no. 9, p. 515-518. DOI: 10.1130/0091-7613.

Labels: alaska, maryland, metamorphism, minerals, structure, xenoliths

Done with the Cockeysville Marble and fortified with chocolate malts from the Twin Kiss, we ventured on to "Mineral Hill," interpreted as a paleo-black-smoker site from the deep Iapetus. This is a zone of mafic and ultramafic rocks that have been metamorphosed and also mineralized with a suite of sulfide minerals, including pyrite, chalcopyrite, bornite, covellite, and carrollite (in fact, this is the type locality for carrollite). Presumably it was a SedEx-type deposit in the Iapetus Ocean basin. It is geographically associated with the Baltimore Mafic Complex, which is most readily interpreted as a dismembered slice of the Iapetus oceanic lithosphere (that is, an ophiolite). As the Iapetus closed during the Taconian Orogeny, it was accreted to North America and metamorphosed.

The petrology students start picking up pieces from the massive pile of tailings in search of treasures:


Talc shist (soapstone) with malachite:


More of the same:


I forget what this one was, but I loved the "spray" pattern of its bladed crystals:


Chrysotile asbestos:


Pyrite:




And lots and lots of magnetite! These are some of my refrigerator magnets stuck to it:


One more stop to go: the Ellicott City Granodiorite...

Labels: appalachians, maryland, metamorphism, minerals, ophiolites, ordovician, ore

For a few months now, prompted by a comment on one of my blog posts from fellow geoblogger Bryan, I've been listening to the Skeptics' Guide to the Universe podcast. It's pretty darned good. Last week, the team interviewed Seth Shostak, senior astronomer for SETI, who made an offhand statement that there was "plenty of bauxite" on the Moon. Considering that the moon's anorthosite has plenty of aluminosilicate minerals, but none of the tropical rains required to produce a secondary concentration of gibbsite, bohemite, and diaspore, a.k.a. bauxite, I wrote in to compliment the show in general but correct this one small tidbit. This week on the show, they acknowledge my correction, though (of course) they mis-pronounce my name. It starts at 25:35 into the podcast. Ah well -- my own little cross to bear. Glad to help advance human understanding of geological processes!

Labels: astronomy, minerals, moon, ore, podcasts and vodcasts, science and society

Yesterday, I showed you the Port Deposit Tonalite, stop #1 on the University of Maryland's annual ig/met pet trip. Today I'll share pictures of the next stop. We voyaged to the Hunt Valley Shopping Mall, where a lovely exposure of the Setters Schist can be found.

It's a lovely example of a classic-looking muscovite schist:


It is also chock-full of garnets! Millions and millions of them....

Some are small:


Some are medium:


Some are large:


Some are fresh:


Some are weathered:


Some are weathered-out:


There's also staurolite present:




Here's a nice big chunky staurolite:


In one localized zone, we also see some very big, rather lovely kyanite:




...Awesome! I love this suite of metamorphic minerals!

The Setters Schist is a highly metamorphosed pelitic rock (meaning that its protolith was clay-rich). It was presumably metamorphosed in the late-Ordovician-aged Taconian Orogeny, like everything else in the Mid-Atlantic Piedmont.

Next up, another member of the Glenarm Series, the Cockeysville Marble...

Labels: appalachians, maryland, metamorphism, minerals, ordovician, piedmont

The April meeting of the Potomac Geophysical Society will be held April 16th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room. This month's talk will be: Mapping Rocks and Minerals using Advanced Spaceborne Thermal Emission and Reflection Radiometer data, by John 'Lyle' Mars (USGS, Reston, VA).

Abstract:
The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) measures reflected radiation in 3 bands in the 0.52 to 0.86 micrometer wavelength region (VNIR); 6 bands in the 1.6 to 2.43 micrometer wavelength region (SWIR); and 5 bands of emitted radiation in the 8.125 to 11.65 micrometer wavelength region (TIR) with 15-m, 30-m, and 90-m resolution, respectively. ASTER also has a backward-looking VNIR telescope with 15-m resolution. The swath-width is 60 km, but off-nadir pointing capability extends the total cross-track viewing of ASTER to 232 km. ASTER VNIR bands are positioned to delineate Fe absorption features, ASTER SWIR bands can delineate Al-OH, Fe Mg-OH, H-O-H and CO3 absorption features, and TIR bands are particularly useful for mapping Si-O vibrational features. This talk will demonstrate techniques and results of minerals and lithologic mapping using ASTER data. Mineral and lithologic maps compiled from ASTER data include parts of the western U.S., Afghanistan, Iran, Kazakhstan, Morocco, and Pakistan. Mapping algorithms include band ratio, matched filtering, and logical operators. Minerals and mineral groups mapped using ASTER data include, muscovite, argillic and phyllic-altered rocks, carbonate rocks, hydrothermal quartz, and quartz-rich rocks.

Biographical Information:
Lyle Mars is currently a Research Geologist in Remote Sensing at the USGS. He got his PhD from the University of Kentucky in 1995. His research is focused on gaining a better understanding of the spectral characteristics of a wide range of earth materials and how these characteristics are remotely sensed. This work is enhancing our abilities to identify important mineral resources, elucidate global tectonic relationships and facilitate recognition of environmental degradation related to mining. He investigates the spectral properties of rocks, minerals and vegetation and applies spectroscopic observations to research in multispectral and hyperspectral remote sensing studies. Most of his remote sensing projects are focused on spectral data in the 0.35 to 14.0 micrometer region. This research is applied to new remote sensing techniques in the identification of minerals, rock types, stratigraphy, structures, and vegetation. His spectroscopic research is also used in the calibration of new remote sensing systems such as the Advanced Spaceborne Thermal Reflection and Emission Radiometer (ASTER), Hyperion, and Hymap. Prior to USGS he was a Visiting Assistant Professor at George Mason University.

Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day. If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 703-676-4373 or via E-mail at Joydeep.bhattacharyya@saic.com. If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site for new meeting announcements, etc. Please send changes of address or email to Joydeep.bhattacharyya@saic.com.

Labels: minerals, pgs, satellite imagery

An article in today's Kids' Post discusses rock collections.

Hat tip to Brian R!

Labels: dc, minerals, teaching, virginia

The Association of Environmental and Engineering Geologists is having NOVA adjunct geology instructor Steve Stokowski talk at their meeting on Thursday. His topic blends petrology (the study of rocks) with applied science.

Sexy Pictures, Busted Bridges, Broken Buildings, and Messed-Up Monuments: A Petrographic Odyssey

Microscopic analyses and geologic understanding are essential for the correct diagnosis and corrective actions necessary when rock, brick, concrete and similar building materials deteriorate, as these four case histories illustrate. The first case history is of the deteriorated brownstone loggia at the Oakes Ames Memorial Hall, North Easton, MA. The second case history is of a total replacement failure of a large memorial to WWII veterans in the Rhode Island Veterans Cemetery, Exeter, RI. The third case history concerns the use of defective, cracked, and residually expansive brick to construct the Prospect Mountain High School, Alton, New Hampshire. The final case history concerns deterioration of the 1930's Fore River Bridge between Quincy and Weymouth, Massachusetts. It can be expensive to correct the effects of the deterioration of common building materials!

Pulcinella's Restaurant
6852 Old Dominion Drive
McLean, VA 22101

AEG members, guests $30.00
Students $10.00

6 p.m. to 7 p.m. Social Hour and Section Business
7 p.m. to 8 p.m. Dinner
8 p.m. Presentation
9 p.m. Closing Statements

Labels: geology, meetings, minerals, science and society

Sorry for the late notice... this is for today at lunchtime.



Abstract: The Silver Hill Mine in Davidson County, North Carolina was the first important underground silver mine in America. Discovered in 1838, it produced significant quantities of silver and lead into the mid-1840's. As the oxidized ores were depleted, abundant, rich, lead-zinc sulfide ores were encountered. These complex primary ores presented the mine operators with difficult metallurgical problems. Mine development and production slowed. Nearly a decade passed as the owners experimented with new processing and smelting technologies. These efforts were largely unsuccessful and the mine closed in the early 1850's. The Civil War created an urgent need for lead to supply Southern troops. The Confederate government operated the Silver Hill Mine to provide an alternate source of lead in case the mines at Austinville, Virginia should fall into Northern hands. Lead concentrates with high silver values were shipped from Silver Hill to the newly constructed Confederate smelter in Petersburg, Virginia. After the War, the mine continued to operate for several years but the problems of the refractory sulfide ores were not solved and the mine closed again. For more than a century after production stopped, the Silver Hill Mine was the repeated target of both mining companies and stock promoters.

Where: Pier 7 Restaurant, 650 Water Street, SW, Washington, DC (within walking distance of the Waterfront Metro on the Green Line) Free parking with validation from Pier 7 Restaurant.

11:30 - Social 12:00 - Lunch 12:30 - Speaker

Meeting cost: $20.00 for Washington, DC Section SME members $25.00 for non-members

Contact Steve Stokowski with questions

Labels: dc, history, meetings, minerals, mining, north carolina

Last month, when hiking Iliniza Norte, a 16,997' volcano in Ecuador, we got up near the summit and began scrambling over the rocks there. Conditions were cold and snowy, and I was pleased to see some beautiful ice formations in protected nooks in the rock. These crystals of ice had a gorgeous branching pattern...



To show this branching pattern close up, here's Lily's gloved hand holding two such crystals (fused together). They look like squirrel tails!



The backdrop of oxidized porphyritic andesite (hosting lichens) isn't bad either.

Labels: ecuador, ice, minerals, travel

Labels: antarctica, astronomy, australia, basalt, gsw, hadean, igneous, isotopes, meteors, minerals

There's a proposal to turn the Luck Stone diabase quarry south of Leesburg into a big reservoir for increasingly-populous Loudoun County, Virginia. It would then be followed by other tapped-out quarries in the area. Collectively storing 8 billion gallons, the reservoirs could serve the surrounding area for up to 120 days during a prolonged dry spell. The idea is to create the reservoirs by siphoning of about 40 million gallons a day from the Potomac River, starting in 2017.

These diabase intrusions are mafic igneous rocks that intruded into the crust during the opening of the Atlantic Ocean. As Pangea broke apart during the Triassic and Jurassic, a huge system of sags opened up in the crust. These low spots were the sites of (a) intense sedimentation, since water flows downhill, and (b) mafic igneous intrusions, since the thinned crust allowed decompression melting of the underlying mantle. (Partial melting of an ultramafic source usually yields a mafic distillate.)

The entire system of failed rift valleys extends along the same trend as the Appalachians, but further east, all the way up to the Bay of Fundy. Collectively, they are called the Newark Supergroup, after one of the larger rift basins in Newark, New Jersey. Dirty sandstones filling that basin were the source of all the 'brown stone' that made the brownstones of New York City. Locally, in our own Culpeper Basin, the main rock that is quarried is diabase, which has a coarser crystal size than basalt, but smaller crystals than a gabbro. It is distinguished by a lot of pyroxene.

Source for the reservoir proposal news: Today's Loudoun Extra, from the Washington Post

Labels: atlantic, culpeper basin, jurassic, minerals, mining, new jersey, new york, news, triassic, virginia, water resources

Quick quiz!

What does this...


...have to do with this?


A mineral's habit is the shape that a crystal of that mineral will attain if it gets the chance. When most people hear the word "crystal," the image that comes to mind is of a mineral crystal that has attained its full habit. However, most crystals aren't that pretty. If there aren't enough elemental ingredients, or if there isn't enough time to grow nice and big, or if there are other crystals in the way, then you won't get a nice, sexy crystal. Instead, the mineral crystal's internal structure will fill in whatever space it can, and that will determine its shape. The lower image shows a cartoon of a thin section of rock. In it, you can see a mineral with a "hexagonal" habit, but this actual crystal's shape is jagged and irregular, as dictated by the space available to grow. Most mineral crystals are like this: stunted and "misshapen" as a result of their circumstances.

And that brings us back to the upper image... the square watermelons. As everyone knows, watermelons are approximately ellipsoidal in shape, if given the chance to grow into their full "habit." However, that ellipsoidal shape is tough to cram into a small fridge; it occupies a larger space than its bulk actually takes up. There's a lot of wasted fridge space in the areas adjacent to it. In Japan, a solution has been developed: grow the melons in boxes, so that they are forced to take on a square or rectangular shape. Then, when mature, Japanese consumers can put the square melons in the fridge, confident that no space is being wasted: the melon is taking up almost all of the fridge volume given over to its storage!

Like most minerals, the Japanese watermelons are constrained by their circumstances to grow into shapes that they wouldn't attain on their own.
____________________________
Image sources:
Japanese watermelons - Oddee.com
Thin section cartoon - me, redrawn from a figure in Marshak, 2006.

Labels: analogies, art, japan, minerals, teaching

Just wanted to let readers know that my "mineral evolution" cartoon is now up at the EARTH magazine website, accompanying their article on the new study by Bob Hazen about how the planet's suite of minerals has (a) changed over time and (b) been influenced by biologic processes.

Labels: art, evolution, humor, minerals

As I mentioned a few posts back, I spent the week of Thanksgiving on the big island of Hawai'i. I had an exam scheduled in one of my classes, and I pre-recorded the lecture for my other class (via Smartboard), so I was free to kick back and relax on my travels. However, I find it's difficult to turn the inner geologist off, and so I spent a lot of my time checking out the cool geology of this unique island. I've got a lot of photos to share and stories to tell, but I'll start off simple: here are sand samples from four beaches in Hawai'i:






As you can no doubt tell, these sands are dominated by, respectively from top to bottom: calcareous hash (fragments of shells and corals), basalt fragments, olivine crystals flavored with basalt fragments, and a greater proportion of olivine crystals. They are respectively from "Sixty-Nines" Beach (west side of island; named for the milepost on the nearby road, so get your mind out of the gutter), Punaluu Harbor (south side of island), Green Sands Beach (south side of island), and a nameless cove between Green Sands and Ka Lae (a.k.a. South Point, on the south side of the island -- and in fact the southernmost point in the entire United States).

Labels: hawaii, minerals, oceans, sediment, tech, travel

Yesterday, I pulled up the Venetian blinds in my office window at NOVA, and this is what I saw:


Naturally, I had to take a photograph. It's puuurty.

While I had the camera out, I figured I'd shoot a few photos of the rest of my office, since it's full of all sorts of interesting clutter. Rather than explaining what all the doodads are in these photos, I figured it would be more fun to just post them and see if you can identify them all:















Have fun!

Labels: fossils, igneous, maps, metamorphism, minerals, nova, plants, sediment

Several years ago, (former) NOVA student Theresa R. put together a nice little webpage with rock and mineral photos. My favorite part is a "gray rock quiz" at the end. Check it out and see how well you do!

Labels: igneous, metamorphism, minerals, nova, sediment, websites

This weekend, I spent three days on an extended field trip down to southwestern Virginia with NOVA adjunct geology instructor Chris Khourey and four of my Honors students. We left Annandale on Friday morning, and made our first stop at Willis Mountain, Virginia, site of one of the most productive kyanite mines in the world.

Here's a Google Map of the mountain:


The Kyanite Mining Corporation was very gracious in hosting us. I'd particularly like to thank Mike Morris, who took two hours out of his day to show us the site and the mining operation.

Why mine kyanite? It's used as a refractory mineral: that is, one that won't melt under high temperatures. A lot of their kyanite is heated in kilns to produce a second mineral, mullite. The mullite is even more stable than kyanite in high temperature refractory situations. (It won't melt until it hits over 1800 degrees C!) Additionally, they cleverly saw up big blocks into dimensional stone for countertops and the like.

The kyanite mined at Willis Mountain is in a quartzite which also includes a fair amount of pyrite and hematite. We heard about the different procedures used to extract the non-kyanite minerals so that their end product is relatively pure and of constant quality.

Here's Mike showing the overall anticlinal shape of the deposit:

It's a plunging anticline, as you can probably make out from the Google Map terrain view up top.

Some of the dimensional stone, which I think is pretty spectacular:


Close up of the kyanite (light blue, on left) in the dimensional stone.


Nearby Baker Mountain also hosts kyanite deposits, which show a deeper blue color (Mike wasn't sure why, but suggested that chromium may be responsible):


Inside a huge storage building where the mullite (white powder at our feet) is stored:


Atop Willis Mountain itself, showing the weathered kyanite quartzite exposed there:


Honors students ask questions of Mike:


Mike and Chris standing near some fresh boulders of kyanite quartzite:


It wasn't all metamorphism and mining... I also noticed these nice raindrop impressions in a drying mud puddle:


After lunch atop the mountain, we hopped back in the van and hightailed it for southwestern Virginia, on our way to the Virginia Geological Field Conference. More on that tomorrow.

Thanks again to Mike and the good folks at the Kyanite Mining Corporation for hosting our visit!

Labels: conferences, economics, field trips, metamorphism, minerals, nova, piedmont, teaching, virginia

Yesterday I noted that there's an interesting pattern to be seen as one crosses DC's Duke Ellington Bridge:

After sharing these photos yesterday, I posed question for you: What's up with the coloration of these exposures? Why are they black on top and white on bottom? It's the same rock (Indiana limestone), so why the difference in color?

The answer has two parts. First, the calcite (calcium carbonate) which comprises the limestone is sitting out there in the air, and is subject to rain and what-not. Some of that rain has sulfuric acid in it, and that dilute sulfuric acid reacts with the calcite, producing a thin layer of gypsum (calcium sulfate). Those itty-bitty crystals of gypsum have bladed habits, and those bladed crystals are really good at trapping soot and dust. So while the calcite underneath isn't as effective as a soot-trap, the thin layer of chemically-altered gypsum on the surface of the blocks rapidly accumulates dark-colored particulate matter.

So that explains the dark color, but what about the lighter-colored lower portions? Is it simply that they aren't exposed to as much acid rain? Perhaps because they're further down on the "outcrop"? Nope... though that's clearly a consideration (note the thin white vertical lines below some of the stars), it wouldn't explain the abrupt transition from dark colored above to light-colored below. So: what gives?

It's here that context plays an important role. This is an urban location, an outcrop in the city. Like many flat surfaces in the city, it's subject to being tagged with graffiti. Periodically, the City sends along a crew to power-wash the bridge's graffitied surfaces. When they do this, they strip away not only the spray-paint, but also the gypsum and its trapped soot! Because graffiti artists can only reach so high, the city only power-washes so high, and the upper portion of the bridge "outcrop" is both unmolested by graffiti and uncleaned by the City. It records a continual accumulation of gypsum and soot, but the lower portion has its proverbial slate cyclically wiped clean!

I'm on a field trip this weekend (I wrote this post on Thursday and set it to publish while I was away), so I don't know who won the prize (a "GEOLOGY ROCKS" bumper sticker!) but as soon as I get back, I'll settle up with the clever winner. In advance, I'll congratulate you: Nice job!

Labels: contest, dc, limestone, minerals, sediment

Tuesday, I asked for my fellow geo-bloggers' favorite analogies, with a promise that I would share mine in 48 hours. The time of revelation is nigh... Here are a few of my favorite "geo-nalogies":

The continental crust is high-proof liquor
I see partial melting as a kind of distillation. Just as "sour mash" can be distilled to concentrate the alcohol it contains (separating it from the water it's dispersed in), so too can partial melting act as a "distillation" of the silicate earth. The minerals with the lowest melting temperatures will melt, leaving behind a solid residue enriched in Fe, Mg, Mn, and Ca, and yielding a magma that is enriched in Si, K, Na, and O. With its~granitic composition, the continental crust is 80-proof Jack Daniels. Where did it come from? It's distilled from the sour mash we call "the mantle":

Rocks are cookies
I love a good chunky cookie. Save your Oreos and Lorna Doones for yourself. What I really like is one of those cookies with chocolate chips, oatmeal flakes, raisins, macadamia nuts, and those sinfully good butterscotch chips. What I like about these cookies is not so much how they taste, but how I can tell the difference between the individual ingredients and the cookie they comprise. I use this analogy early on in Physical Geology to illuminate the difference between minerals and the rocks that the minerals comprise:

Continents are old sofas
Like many of us, I had an old sofa in college. The sofa was ripped, had been scratched by a cat, and had coffee spilled on it. It was draped in several layers of blanket in an attempt to cover up the lousy state of the upholstery. Someone added a pillow to the sofa at some point. When I was working for the C&O Canal National Historical Park (translating their geologic history into non-geology-speak), it struck me that the North American continent* was kind of like that old sofa. It had been scratched by glaciers instead of cats, and lava had been spilled on it kind of like that errant French Roast. It had rift valleys, but unlike the sofa's, North America's rifts didn't have springs poking out. New material had been added in the form of exotic terranes, kind of like that pillow got added to the sofa. And the blankets draping parts of the continent were made of sediment instead of fabric... but essentially the two were alike:

*Yes, I know that's the outline of the contiguous 48 United States, not North America the continent. So shoot me.

Tectonic plates are UFOs
In cross-section, a tectonic plate could be seen to have a profile kind of like a flying saucer. The thick part in the middle is the continental crust, but then it has a thin fringe encircling it (the oceanic crust). You can hardly blame a visiting Martian for feeling kind of attracted to it:

The Washington Monument shows geologic time
I didn't come up with this one... But read it somewhere (McPhee, maybe?) that I have since forgotten. Anyhow, the basic idea is that the Washington Monument's obelisk here in Washington, DC can show the difference between the Precambrian portion of geologic time (most of the monument, 88% of Earth history) and the Phanerozoic eon (post-Cambrian, 12% of Earth history). The little pyramid-shaped bit on top is the Phanerozoic. The thickness of a single sheet of paper draped on top of the tippy-top would represent the entire span of human history:

Okay, that's all I've got for today. What have YOU got?

Labels: analogies, geologic time, geology, granite, minerals, teaching

Yesterday's mineral meme spread like wildfire!

Brian at Clastic Detritus, Kim at All my faults are stress-related, MJC Rocks at GeoTripper, the Lost Geologist, Chris at Highly Allochthonous, Dave at Geology News, me here at NOVA Geoblog, Silver Fox at Looking for Detachment, ReBecca at Dinochick Blogs, and A Life-Long Scholar at Musings of a Life-Long Scholar all followed the inaugural post by Chuck at Lounge of the Lab Lemming in offering a list of fifty minerals they thought others should see before they die...

It's interesting to see the different ways people interpreted the point of the exercise. A lot of folks copied Chuck's list and then changed the formatting (bold, italics, etc.) to match their experiences with the minerals, while others of us made our own list of what we considered important. This latter approach was the one I followed, but I confess to copying Chuck's list and then going through it to figure out which ones I felt deserved to be in the "top fifty" based on my own experiences. I deleted some, and added new ones in their place. I wonder if I would have gotten a different list if I had started from scratch. I'll bet I would have come up with some different minerals, like chlorite. So far as I can tell, chlorite didn't make anyone's list... but I would argue it's a pretty important mineral, especially in the Appalachian mountain belt. Given the option to revise, I'd probably drop azurite off my list, and put chlorite in that spot instead.

So let me issue a new challenge for my fellow geobloggers... Which five minerals do you think are the most important ones to know, and why? In other words, if you had to introduce a non-geologist to just five of the earth's multitudinous building blocks, which ones would you choose to share, and offer a justification for each.

Mine:

1.) Quartz: Toughest major (zircons are minor) constituent of the continental crust, most stable at Earth-surface conditions of temperature, pressure, humidity, etc. It's pretty much at equilibrium at the surface of the Earth, so while feldspars and amphiboles and what not break down into clay and rust and ions, quartz sticks around unchanging. Hence, mature terrigenous sedimentary rocks contain a high proportion of quartz.

2.) Clays: Ditto: stable at the Earth's surface.

3.) Plagioclase feldspar: The most common mineral in the Earth's crust. Why? It's made of the most common elements in the Earth's crust, and is versatile in its composition, depending on what ions are available to fill in the appropriate gaps in its crystal lattice (K, Ca, Na).

4.) Olivine (also maybe Garnet, Spinel & Perovskite?): Major constituent(s) of the mantle, the most volumetrically significant portion of our planet. Compared the portion of our planet that is ultramafic, the quartz and clays are diddly-squat. We may not live in the mantle, so it's less familiar... but Earth is mostly mantle, so it's important to know what minerals make it up.

5.) Ice: Possibly the mineral we encounter most frequently in our lives, and for many people a surprising member of the mineral list. Ice has played a major role in Earth history (glaciations in the Paleoproterozoic, Neoproterozoic, Paleozoic, and Pleistocene), the important role of ice in determining sea level (of consequence in the modern day's episode of climate change), the usefulness of ice melting/freezing in teaching about other minerals melting/solidifying, the unique nature of ice being more voluminous (lower density) than liquid water (which essentially has allowed freshwater ecosystems in temperate climates to survive, because they freeze from the top down, rather than the bottom up) and the fact that ice helps make a margarita the splendid thing that it is.

What are your Top Five?

Labels: blogs, minerals

An interesting development in the geoblogosphere today. Everyone's posting lists of their "fifty great minerals," where "great" is left in the eye of the beholder/blogger. So far the following geobloggers have offered their lists: Lab Lemming, Hypocentre, & Silver Fox. I'll jump on the meme wagon, too...

Minerals in bold are those I've seen in the field, while italics indicate sightings in the lab or museum. My fifty:

Augite
Azurite
Barite
Beryl
Biotite
Calcite
Chromite
Chrysotile
Clays
Corundum
Diamond
Dolomite
Epidote
Fluorite
Galena
Garnet
Gold (native)
Graphite
Gypsum
Halite
Hematite
Hornblende
Ice
Kaolinite
Kyanite
Lepidolite
Limonite
Magnetite
Malachite
Monazite
Muscovite
Olivine
Opal
Orthoclase ('potassium') feldspar
Perovskite
Plagioclase feldspars
Pyrite
Quartz
Rutile
Sillimanite
Sphalerite
Spinel
Staurolite
Sulfur (native)
Talc
Tourmaline
Tremolite
Vermiculite
Zeolites
Zircon

Labels: blogs, minerals

When I look back on my four years of undergraduate geology education, the one thing that strikes me as the most important thing I learned is the age of the Earth. It sent my mind reeling to recognize what a huge old planet I was on, and how ephemeral was my own species' time on it. I was a blip, a temporary arrangement of carbon, hydrogen, oxygen, and a handful of other elements that would last a while, and then disassociate. Material and energy passed into me, and out. This kinetic chemical phenomenon known as me would soon pass, and the Earth would keep turning. The human species would reach its zenith, then collapse (or evolve into something else), and the Earth would keep turning. The continents would rift and crash and the map of the Earth would soon be obselete, and the Earth would keep on turning. Climates change, meteors hit, "rivers shift, oceans fall, and mountains drift" (REM, 1985), and still the planet keeps on spinning, keeps on orbiting, keeps on keeping on.

The day I really realized the age of the Earth wasn't the day I heard "4.6 billion" in lecture. It was the day I sat there studying and grasped it internally -- it clicked that it was immensely, unimaginably old. My temporary human mind was a short-time-scale phenomenon, and it was impossible for this small cerebral system to get a grip on the true scale of the planet's age. While I would never really know (comprehend/appreciate) the age of my planet, I tapped into something fundamental that day. Looking back on it now, I'm reminded of John Playfair's words when his pal James Hutton took him to Siccar Point for the first time: "The mind seemed to grow giddy by looking so far into the abyss of time" (1805).

When I made that cognitive leap (by essentially realizing it was impossible for me to fully make the cognitive leap), I got stuck on geology. I connected to the study in a way I hadn't done before. Suddenly I was subject to a dizzying temporal vertigo, as if a layer of flooring had crumbled away leaving me gazing into a bottomless pit. The realization gave a whole new perspective on things, and it was exhilarating. It felt like one of the conversations when you're getting to know someone, and realizing that they are both intriguing and yet never completely knowable. It draws you in, connects you. Without getting too gushy, it's kind of like falling in love. I've been a geologist ever since.

As I learned more, both in school and on later peregrinations around the world, I found that geology was a great traveling companion. No matter where I went, geology was there with me, showing me new things, giving me insightful perspective. I was looking at the world through geology-colored glasses, and finding that it had a lot to show me. The world made more sense on an elemental level. Hills made sense; rivers made sense; mountains made sense. While I couldn't claim to fully understand any of these phenomena, I could claim a connection to them now that wasn't there before. They were no longer random in my mind; they had a place in the overall system, and it took geology to make me realize it.

So this perspective has stuck with me, and it's what inspired me to pitch "geology as a connector" as this month's Accretionary Wedge theme. (Newbies: the Wedge is a semi-monthly geoblogosphere carnival wherein different geobloggers contribute posts organized around a central theme.) I was curious about what I would get, and I didn't want to restrict my peers' submissions by specifying what kind of connections should be written about.

Sure enough, different people interpreted connection differently. Tromping around in the mountains doing geologic mapping yields more than insights into local structure and stratigraphy, as BrianR of Clastic Detritus discusses how his field work has connected him to the messy reality that is nature.

Jess at Magma Cum Laude is starting her first semester as a graduate T.A., and is going to employ a teaching technique that connected her to the pervasive nature of geology: everything that the Earth puts out for the purpose of assembling Oreo cookies. Something as simple as an Oreo can be the vehicle through which students realize the manifold ways they depend on the Earth every day.

Where are the boundaries between sciences? Is geology a subset of environmental science, or physics? Or both? How do we define the different parts of Nature that we study? Using a Venn diagram, Hypocentre at Hypo-theses explores the connections between geology and other sciences, particularly in the environmental realm.

Similarly, Mel uses a diagram to explore connections in her post at Ripples in Sand. How does geology connect to paleontology? Join Mel in looking at the taphonomic bridge. (And wish her congratulations on her wedding while you're at it!)

Joining the crowd in her first Accretionary Wedge post, A Life Long Scholar (at The Musings of a Life-Long Scholar) makes a connection between the very small and the very large. In trying to answer questions about massive tectonic plates, sometimes geologists must turn to little bundles of mass a few micrometers across. Check out her post to see how garnets can reveal the secret histories of the continents.

And then there are the personal connections. In Looking for Detachment, Silver Fox was the first one to submit a post on the "connection" theme with her description of how different members of the mining and exploration community connect to one another over time and space (Nevada, of course). How do Charles Manson, Kevin Bacon, and exploration geologists all fit together? Read her post to find out.

MJC Rocks of the Geotripper blog has contributed a real treat: an exploration of the connection of geologists teaching geologists through time. It turns out that his academic lineage goes all the way back to Agassiz and Cuvier! A pretty impressive consideration which will surely inspire the rest of us to investigate our own geologic pedigrees.

Finally, over at Harmonic Tremors, Julian shares a story of how his knowledge of geology led him to make a personal connection with one of his cinematic idols, director Brad Bird. If you've seen the Incredibles, you're familiar with Bird's high quality entertainment. When Julian heard that Bird was working on a movie called 1906 about the great San Francisco Earthquake, he wrote a letter to clear up some inconsistencies in the book upon which the movie is based. The talented director took the time to write back to Julian, thanking him for the "seismic tutorial."

Enjoy the various and sundry posts -- follow these digital connections to other geologists in other parts of the world, and feel connected to the larger community of earth scientists. Thanks to everyone who contributed. If I've missed anyone or if anyone wants to submit a late post, give me a shout or post a link in the comments.
________________________
References:
Playfair, John (1805). Transactions of the Royal Society of Edinburgh, vol. V, pt. III.
REM, (1985). "Feeling Gravity's Pull," Fables Of The Reconstruction, IRS records.

Labels: blogs, earthquakes, field trips, geology, metamorphism, minerals, mining, movies, plate tectonics, teaching

Sorry for the long delay in posting here. Turns out they don't have Wi-Fi at Phantom Ranch.

After my time in Zion (did Angels Landing and a few other small hikes while there), I scooted down to Las Vegas, Nevada, to pick up my father and two brothers. They had flown in there, and after one day were already tired of the city. I was ready to leave five minutes after I got there, which is always how I feel about Vegas. Somehow, circumstances keep conspiring to bring me back there, though...

We drove out of the Basin & Range and up onto the Colorado Plateau, and spent the night at Cliff Dwellers, a lodge near Marble Canyon. I was really impressed with their food and drink. We had an amazing meal, washed down with several pitchers of Newcastle Brown Ale! In the morning, we gathered up our gear and put onto the river. Our trip consisted of two rafts outfitted with side tubes and motors and guides. One raft was entirely made up of a family from Charlotte, North Carolina, including the glass artist Wayland Cato, III. The Bentley's raft was augmented by a family from Littleton, Colorado, two oil men from Oklahoma, and a couple of veteran river rafters from northern California. It was a motley crew, but we started having fun immediately.

We launched at Lees Ferry, in the Kaibab Limestone, and then descended in both elevation and geologic time. At our first lunch stop, in the Coconino Formation, I was astonished at several synapsid reptile trackways protruding from the underside of the paleo-dune slipfaces overhead. I took some photos, but because of the aforementioned software issue, I won't be able to share them until I get back to DC in August. As the first couple of days went by, we just went deeper and deeper into the Paleozoic stratigraphy of the Colorado Plateau. Of all the formations, my favorite was the Bright Angel Shale, which has many beautiful colors in thin layers throughout (not to mention oodles of trace fossils). I was particularly pleased to play frisbee in a "cave" in the Redwall Limestone, a place that I have shown photographs of to my students, but never actually seen before. It's a HUGE cliff of the Redwall, and then this seemingly small cave etched into its base (and filled with sand), but the cave could easily swallow my building at NOVA: it's big!

At some point, we crossed a major fault, and were instantly dropped down about a billion years in geologic time. Once we got into the Grand Canyon Supergroup and the metamorphic and igneous basement rocks, my geologic interest really went wah-wah. The Vishnu Schist and Zoroaster Granite make a stunning contrast: really beautiful pink cutting across dark grey. I introduced my raft-mates to the idea of the Mazatzal Orogeny, and we discussed how boudinage forms. There were faults and folds galore: structural paradise. I loved it.

Did I mention the rapids? There were rapids. The water was COLD, thanks to Glen Canyon Dam(n). But the sun was hot, and we dried out quickly. Meals were gourmet, though the campsites were spartan (you had to poop in a box that got packed onto the raft each morning: leave no trace!). We slept out under the stars every night, sometimes dealing with blowing sand.

We took several hikes up side canyons to see waterfalls and go swimming. Several of these were good and physically challenging, which is what I wanted. I enjoyed swimming and playing "three-dimensional frisbee" in Havasu Creek, and doing cannonball jumps in the weird blue of the Little Colorado River.

The final day on the river, we came to the western section of the Canyon where recent lava flows (basalt) have cascaded over the rim and down into the canyon. This is famous for producing one of the toughest rapids in the whole Grand Canyon: Lava Falls. But it was awesome to float by and see umpteen gazillion columnar joints, and whole feeder canyons plugged up by basalt. Pretty cool!

Our final morning, we were helicoptered out of the Canyon to a ranch on the rim. This was my first time in a helicopter, and it was giddy and amazing. I want to fly! From the ranch, we transferred to small fixed-wing planes, and I said goodbye to my family. They went back to Vegas, and I flew back to Cliff Dwellers, where my Prius (and a shower!) awaited.

Labels: fossils, geology, grand canyon, minerals, primary structures, rivers, sediment, travel, volcano

Roadtrip update:

Yesterday was a good one. I started off the day at the Sternberg Museum of Natural History in Hays, Kansas. I was the first one in the door, and had the place essentially to myself. Massive mosasaur skeletons, supercool Uintacrinus slabs, plesiosaurs, and all kinds of other neat stuff. They had some less spectacular mineral displays, but the locally-derived fossils were world class. I was very impressed.

Then, driving. I made good time when the wind wasn't trying to stop me, and listening to Bill Bryson's A Short History of Nearly Everything on my iPod, I crossed into Colorado. Eastern Colorado looks a lot like Kansas, of course, but before too long had passed, I got my first view of the Rockies in the distance, "rising from the plains." I got to the Denver area around 2pm, which meant I had plenty of time before the 7pm "Geography Goes Digital" event at the Denver Museum of Nature and Science (DMNS). So I headed southwest, towards Morrison, Colorado, and "Dinosaur Ridge." Dinosaur Ridge is a hairpin driving loop on/over the Dakota Hogback, showing Mesozoic sedimentary rocks shed off the Laramide Orogeny and into the Western Interior Seaway. There's an excellent display of dinosaur tracks, and lots of cool ripple marks, trace fossils, concretions, and stratigraphy. Looking out over the crisp dry air of the Denver Basin, I really felt like "Aha! I'm finally in the West!" It was a good feeling. After hiking and exploring there, I toodled into Morrison, Colorado, and went the Morrison Museum of Natural History. There, I had the terrific good luck to run into Matt Mossbrucker, who I mentioned reading about in Smithsonian magazine back in April. The museum's volunteers were on vacation, so I had the good fortune to have a personal tour from the director! Matt showed me a wealth of incredible fossils, including the type specimen of Stegosaurus, and footprints of baby Stegosaurus and Apatosaurus -- the latter tracks were the subject of the Smithsonian article. In case you (still) haven't read the article, it looks like these baby sauropods were capable of running on their hind legs like a basilisk lizard. Matt walked me through the logic, pointing at specific pieces of evidence on the massive slab of rock. Then we were out of time, because I had to get over to the DMNS for the "Geography Goes Digital" event.

At the DMNS, I was met by Kirk Johnson, the author of a book I mentioned here a month or so ago: Cruisin' the Fossil Freeway. My friend Michelle knows Kirk, and put us in touch. (Thanks, Michelle!) Kirk has been at the DMNS for more that fifteen years, starting as a curator of paleontology, and now as a vice-president. It was very cool of him to make time to see me. Immediately, Kirk introduced me to Bob Raynolds, the speaker for the "Geography Goes Digital" event. Bob and I talked a bit about geology and teaching, and then we scooted over to the Planetarium for the main event. I took a seat, leaned back and was amazed. It was like Google Earth on steroids; a feeling like looking down from the space station on Earth. Bob led us on an exploration of areas of the world that are showing the strain of coping with climate change. He has an astonishing amount of geographical knowledge (apparently, he has traveled to more than 50 countries to do geology) and it was a real treat to tour the planet with him and 150 of the DMNS's closest friends. Afterwards, Kirk took me and another friend-of-a-friend visitor on a tour of the museum. I saw the world's second-largest gold nugget, a massive crystal of rhodochrosite, and the incredible tour through time exhibit that Kirk put together when he first got to the museum. Starting with the Ediacaran, the exhibit went through time in a series of sub-exhibits. Each started with a diorama, and then showed the fossils that the diorama was based on. There were some INCREDIBLE fossils there -- absolute stunners. Kirk confided that's just how he wanted it -- not a thousand small fossils, but a few massive ones that just knock your socks off. It was very impressive. Around 10pm, I bade Kirk farewell, and left the museum. I drove up to Boulder, Colorado, and holed up in a hotel for the night.

I feel really lucky to have visited three amazing paleontological museums in one day, and to have had personal tours from the elite of Denver paleontology. Many thanks to Matt and Kirk for making time to show me around!

Now I'm off to check out Boulder, and maybe hike in the Flatirons above town. More later.

Labels: colorado, dinosaurs, fossils, kansas, minerals, travel

While toodling along the web on some other business this week, I stumbled across this publication by the Virginia Department of Mines, Minerals, and Energy.

I had no idea that there were any diamond finds in Virginia. But apparently there are, scattered across three different physiographic provinces!

On Thursday's excursion, Chris and I tried to find the "Front Royal Peridotite," one of seven locations mentioned in the DMME publication. It's a single dike which crosses State Road 626 southeast of Waterlick, Virginia. But to no avail! There were no outcrops visible on either side of the road, and there was a dense little cluster of houses bearing manicured lawns. Bummer. That would have been cool.

I'll try and visit a couple other localities mentioned in the report over the next year or so, and hopefully I'll find some of these igneous source rocks, though I don't hold out much hope of actual diamonds.

Labels: blue ridge, diamonds, minerals, piedmont, valley and ridge, virginia

This is the image on the cover of the April 2008 issue of Geology:

Wow, eh? Here's what they have to say about it: "The image shows a perfectly preserved Devonian phacopid trilobite, which was collected at Hamar Laghdad in Morocco (cephalon is 10.2 mm diameter). The shell is silicified with a high iron content, while the lenses retained their original calcitic composition, hence the color difference. This can probably be explained by the different crystal size and the porosity of the shell. Photo by: Christian Klug and Hartmut Schulze."

Labels: art, fossils, minerals

On Thursday, I posted some reflections on one of the talks at the most recent meeting of the Geological Society of Washington. At the same meeting, there was another talk that got my attention, and I wanted to briefly share its findings with the geoblogosphere. The talk was entitled "Mineralogy of the Atmosphere: Assessing environmental and health impacts of airborne particulate matter." It was given by Reto Giere, of the University of Freiburg, Germany. (He's currently in DC as a Visiting Investigator at the Geophysical Laboratory of the Carnegie Institution of Washington.)

Reto's research has lately focused on particulate matter in the air. He collects it and then evaluates it using transmission electron microscopy, X-ray diffraction, and other techniques. The first point he made in Wednesday's talk is that "soot" is a matter of definition. Natural and anthropogenic sources can both be found in the sub-1-micrometer range. If you look at small particulates, Switzerland's environmentally-lauded train system actually generates three times as much "soot" as their traffic output.

So what's in that "soot?" Turns out that a lot of it is anglesite, PbSO4 and some of it is gunningite, ZnSO4'H2O. (There are also droplets of elemental selenium, Se.) The majority of these metal sulfates (and others) are coming from flue gases from power plants. And the thing is, because they're so small, all these goodies end up in our lungs. Reto has run modeling experiments to see what weight-percent of the average person's dose of inhaled metals gets extracted by the lung fluid. In one week, 80% of the zinc was absorbed by the lungs, 55% of the nickel, and 35% of copper. Yum! (I would have been interested to see the actual masses of these absorbed metals compared to the quantities present in a typical vitamin pill, but that wasn't covered.)

There's good news that stems from Reto's work too: the particular "cocktail" of minerals in a sample may be diagnostic of a specific source, which would be useful for forensic identification of polluters. Overall, I found it an interesting talk, on something I'd never really thought about before.

Labels: environmental, gsw, minerals

So this weekend, as part of my ravenous Netflix consumption, I watched Libby, Montana, a documentary which explores the effects of vermiculite mining in the namesake town. The vermiculite in question is augmented with a less desirable mineral: the amphibole known as tremolite. Tremolite grows in a long, fibrous habit, which has been given the name... asbestos. So the deal with Libby is that essentially everyone in town either worked in the vermiculite mine, or was married to someone who worked in the vermiculite mine. A bunch of them inhaled tremolite fibers, both workers and family members. A bunch of them developed lung diseases like asbestosis or mesothelioma. A lot of them died. The movie ends with a moving tribute to the dead. It's some bad stuff. W.R. Grace, the company operating the vermiculite mine, is demonstrably culpable for their employees' deaths.

Tremolite is one of the nastier varieties of asbestos, but not all minerals that happen to grow in that shape are carcinogenic. Some, like chrysotile, (the variety mined at the type locality) have not been found to be as dangerous (by authorities like the USGS). But because many varieties of asbestiform minerals do cause disease, many people (particularly in the litigious U.S.) have opted to ban all minerals of the asbestiform habit. This has resulted in umpteen gazillion public buildings being stripped of their asbestiform minerals, whether or not those particular minerals have been shown to be disease-causing. It's like banning all round candy just because you think that red M&Ms are carcinogenic (which isn't even true). So this brings us to my home institution of Northern Virginia Community College (NOVA). This week, if you were to come visit me in my office in the CF building, here's what you would see (photo).

We're doing asbestos abatement. Amazingly (from a legal standpoint), I'm still allowed to keep working in my office, ten feet away from a what appears to be a major asbestos removal project. The local source is the floor tiles, which look pretty much like linoleum, but are apparently held together with the strong "asbestos" fibers. Which asbestos mineral exactly? Don't know. Probably never will. Last year, they did the same thing in a separate building, the one where my classes are held.

As a P.S., I'll mention that halfway through the day yesterday, I noticed someone put duct tape over the words "Asbestos" and "Cancer and Lung Disease Hazard." No longer that particular danger, apparently...

Labels: minerals, montana, movies, nova