Okay, so maybe you recognize that. No? Take another look:



That's tafoni, peppering the Bishop Tuff on the volcanic tableland north of Bishop, California. I went there in September as part of a weeklong GSA Field Forum. Tafoni is a distinctive weathering pattern presumed to be caused by salt weathering, often in sandstones. This particular example wasn't in a particularly salty location, and the rock being weathered was the Bishop Tuff, a welded volcanic ash deposit. But it's clearly the tafoni pattern:



Here's some tafoni resources from the geoblogophere:
Through the Sandglass 1
Through the Sandglass 3
Tafoni from About.com 1
Tafoni from About.com 2
The Dynamic Earth 1
The Dynamic Earth 2
A previous mention here on NOVA Geoblog



And one more... ??

...Just kidding. This last one is a metate, a Native American grain-grinding depression. There were a couple of them at this location, too. Like the tafoni, it's a hole in the rock. Unlike the tafoni, it's man-made. Would you believe we didn't go there for the metates or the tafoni, but some normal faults instead? ...I'll have to share them in a future post.

Labels: anthropology, california, conferences, history, travel, weathering

Heh! I love it.

Labels: art, blogs, evolution, history, humor, websites

You should check this out. The illustrations don't reproduce especially well in the PDF, but rest assured they are higher-fidelity in the print edition of the monthly magazine from the Geological Society of America.

It's good to know that some modern workers are following this proud tradition: I'd like to give a special shout out to Bobby Boessenecker, who posted some exquisite sketches on his blog this morning.

Labels: art, geology, history

It's the Earth's "birthday!" Today, October 23, is the anniversary of the 4004, BCE creation of the cosmos, according to Archbishop James Ussher, Primate of All Ireland and Archbishop of Armagh. Ussher is famous for having made a pre-geology attempt to date our planet using a literal interpretation of Biblical scripture and a carefull tallying of "begats." Though a scholarly and noble attempt given the intellectual context of his day, Ussher's ideas were soon supplanted with the discovery of deep time by geological studies, starting ~100 years later with another James, James Hutton. The accepted age of the Earth was pushed back further and further by subsequent geological work, and our currently accepted age for the planet (and the Solar System) is approximately 4.6 billion years. Despite these insights, there are a substantial number of "Young Earth" creationists who stick to Ussher's number, or a similarly itty-bitty age derived from a Holy Book of their choosing. This bizarre contention puts them in the awkward position of having to deny the fossil record, the decay of radioactive isotopes, the expansion of the universe, and (of course!) the evolution of species by mechanisms other than Special Creation by a diety. Because Ussher was a scholar and a thinker as well as a religious man, my suspicion is that if he were alive today, he would reject the close-minded anti-science that so many creationists voice.

I love the fact that Ussher's title was "Primate," considering that the main issue creationists have with evolution is that they don't want to be descended from non-humans. The word primate comes from the Latin for "first" (as in "primary") and reflects Ussher's position at the top of the Church of Ireland, and Linnaeus' view that the primates were "first" among the mammals, an anthropocentric bias that persists in uncountable ways today. The truth of the matter is that humans are primates, and so are baboons, lemurs, gorillas, and yes, even chimpanzees.

Ussher was indeed a primate -- just like the rest of us. Happy birthday!

Labels: geologic time, history, words

After a post the other day, Michael wrote in to ask for clarification of "Pumpelly's Rule."

AGI defines Pumpelly's Rule thusly*: "The generalization that the axes and axial surfaces of minor folds of an area are congruent with those of the major fold structures of the same phase of deformation."

We saw some of this same idea expressed in yesterday's annotated photo series featuring parasitic folds on larger folded (and boudinaged) quartz veins. There were bigger folds there, and then those bigger folds were decorated with little parasitic folds. The idea behind Pumpelly's Rule is that you could get a sense of what the big folds are doing by looking at the little folds. But even more revealing than parasitic folds at the hinge area of a larger fold are the little folds that you sometimes see on the limbs of bigger folds.

Depending on the sense of the asymmetry of these folds, we call them either "S" or "Z" folds. The parasitic folds are more symmetrical towards the apex of the fold, but more asymmetrial along the limbs. Check out this diagram to see how small S-folds and Z-folds relate to the larger structure of the main fold. Blue arrows indicate the relative sense of shear on each limb of the main fold:


Pumpelly's Rule suggests that we don't need to see the whole picture to understand what's going on. Simply seeing the areas of the diagram highlighted in red are enough to give a sense of the bigger picture.

So how does that relate to this photo, which prompted the question?


Behind me in the photo, you can see an outcrop of the Cretaceous-aged Thermopolis Shale, exposed on Bridger Canyon Road, in the southern part of the Bridger Range, Montana. It has some sandstone layers in it. These sandstone layers, with their high color contrast against the surrounding black shale, record a series of lovely S-folds. The strata here dip moderately to the west. The S-folds relate the sense of shear on the larger structure of the Bridgers: they suggest that the bedding here is overturned, and that you're looking at the eastern side of a big north-south-striking anticline. In the southern Bridgers, therefore, the overall structure is an overturned anticline. Hiking west & uphill confirms this interpretation stratigraphically: as you go up, you go "back in time," encountering older and older strata: from the Thermopolis into the Kootenai, into Jurassic formations like the Morrison, the Swift, and the Rierdon.



Moral of the story: small observations can have large implications.

Raphael Pumpelly made this observation in 1894, presumably during his tenure as the head of the USGS New England Branch. Pumpelly sounds like he was an interesting guy, leading expeditions in Asia when that was a seriously sketchy prospect. In addition to his Rule, he is honored with a mineral named after him, pumpellyite.

* If you don't have a copy of AGI's Dictionary of Geological Terms, a good resource for looking things up online is this Dictionary of Mining, Mineral, and Related Terms sponsored by Hacettepe University in Turkey.

Labels: cretaceous, history, jurassic, montana, mountains, structure, websites

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

No need to hear me say it... Get it straight from the source:

Library of Congress Hosts Lecture By Sandra Herbert, Feb. 18

The Science, Technology and Business Division of the Library of Congress will celebrate the 200th anniversary of Charles Darwin's birth with a lecture by Sandra Herbert, one of the world’s leading authorities on Darwin. She will discuss her book Charles Darwin, Geologist, which explores how geology changed Darwin and how Darwin changed science.

Herbert will lecture at 11:30 a.m. on Wednesday, Feb. 18, in the Pickford Theater on the third floor of the James Madison Building, 101 Independence Ave. S.E., Washington, D.C. A book-signing will follow the lecture, and the science reference staff will display Darwin items from the Library's collections. The event is free and open to the public; tickets or reservations are not needed.

In "Charles Darwin, Geologist," Herbert provides a fresh perspective on the life and accomplishments of Darwin, who was born on Feb. 12, 1809 (the same day as Abraham Lincoln) and whose thoughts and theories about the natural world hold true today - 150 years after the publication of his "On the Origins of Species by Means of Natural Selection" (London, J. Murray, 1859).

While Darwin is best known for his voyage on the HMS Beagle, his study of finches on the Galapagos, and his theory of evolution, he had wider interests in the field of science, including geology. According to Herbert, "In the 19th century, geology attracted persons of imagination, like Darwin, because of its promise of knowledge of the distant past." Herbert shows how Darwin's study of geology and his developing ideas about geological systems profoundly shaped his creative insight and scientific methods as he worked toward an understanding of evolution and natural selection.

Charles Darwin, Geologist, written largely at the Library of Congress, won the Geological Society of America's Mary C. Rabbitt Award, the American Historical Association's George L. Mosse Prize and the History of Science Society's Levinson Prize for Historical Work in the Life Sciences as well as the Albion Book Prize given by the North American Conference on British Studies.

Herbert recently retired as director of the program "the Human Context of Science and Technology" and professor of history at the University of Maryland, Baltimore County. She is also editor of the Red Notebook of Charles Darwin (1979) and Charles Darwin's Notebooks, 1836-1844: Geology, Transmutation of Species, Metaphysical Enquiries (1987).

As a Distinguished Visiting Scholar for 2006-2007 at Christ's College in Cambridge, Herbert assisted the university with its plans to celebrate Darwin's bicentennial. Herbert first saw the Charles Darwin Archives at Christ College when she was a graduate student at Brandeis University. The archives contain Darwin's notebooks, papers and correspondence, and when she discovered the material she remembers thinking "It was like finding out Shakespeare had left unpublished plays behind."

The Library of Congress maintains one of the largest and most diverse collections of scientific and technical information in the world. The Science, Technology and Business Division provides reference and bibliographic services and develops the general collections of the Library in all areas of science, technology, business and economics, with the exception of clinical medicine and technical agriculture, which are the subject specialties of the National Library of Medicine and the National Agricultural Library. For more information, visit http://www.loc.gov/rr/scitech.

Labels: evolution, history, meetings

As promised, here's some details for the event I mentioned the other day:

2:15- 4:45 Lisa Williams: Various displays of models, samples, artifacts, posters.
2:15 - 2:25 Bill Stanclift: Piano
2:25 -2:30 Reva Savkar : welcome and introduction of first speaker
2:30 - 2:45 Ralph Eckerlin: "Review of Darwin's life and accomplishments"
2:50- 3:10 Tom Macke: "Lincoln"
3:15 - 3:30 Karla Henthorn: "Common Misconceptions About Darwin"
3:35- 3:50 Jill Caporale: "The poetry in Darwin"
3:55 - 4:05 Nan Peck: "fun Lincoln-Darwin game"
4:10- 4:25 Bill Gorham: "Thomas Henry Huxley: Bulldog"
4:30 - 4:45 Callan Bentley: "Charles Darwin, Geologist"

200th Birth Anniversary of Lincoln and Darwin Celebration: The event will be held in the Ernst Community Cultural Center Forum on the Annandale campus of NOVA, Feb 12, 2009, starting at 2:15pm.

Labels: evolution, history, meetings, nova

My clever & creative colleague Reva Savkar (chemistry) is putting together a celebration of the 200th birthday of two important individuals in the history of the world: Abraham Lincoln and Charles Darwin, both born on February 12, 1809. The event will be held in the Ernst Community Cultural Center Forum on the Annandale campus, starting at 2:15pm.

The details are still being organized, but the event will feature short talks, music, and activities both from NOVA faculty and outside guests. Confirmed so far are: Bill Stanclift, Reva Savkar, Ralph Eckerlin, Tom Macke, Karla Henthorn, Jill Caporale, Nan Peck, and Bill Gorham.

I'll be presenting a 15-minute talk, starting at 4:30pm entitled "Charles Darwin, Geologist."

The event is free & open to the public. Join us!

Labels: evolution, geology, history, meetings, nova

Strange Maps has an interesting piece up today about where West Virginia came from (as a state): turns out it was all about the Civil War. The accompanying map shows the original proposed name for West Virginia, "Kanawha," as well as a proposed demarcation between Virginia and Maryland that trended along the western margin of the Blue Ridge physiographic province. If this boundary had come to pass, Virginia would have gotten the Valley & Ridge province, but Maryland would have retained the Blue Ridge, Piedmont and Coastal Plain.

Labels: blogs, blue ridge, coastal plain, history, maps, maryland, piedmont, valley and ridge, virginia, west virginia

This is how good it is to be a professor on summer break: Yesterday afternoon, after composing yesterday morning's epic account of my Massanutten trip, I toodled on over to the Palisades Museum of Prehistory to (a) drink beer and (b) talk rocks with the museum's curator, Doug Dupin.

The Palisades Museum of Prehistory is in far western Northwest DC, near the Dalecarlia Reservoir and Sibley Hospital. There, you'll find a neighborhood called the Palisades, and in the Palisades, you'll find Doug Dupin's house. In Doug's backyard, you'll find what appears to be a nice shed. Turns out, this is the museum. It's a long story, but basically it boils down to this: Doug was a cartographer, but a contract went sour, and so he was staying at home with a lot of time on his hands. He decided to grow some grapes to make wine, and store that wine in a self-dug wine cellar. He started digging the hole, and encountered arrowheads, pot sherds, and other artifacts. He got intrigued, and decided to showcase the findings atop the wine cellar in a self-made museum.

If you want more details, the Washington DC CityPaper profiled Doug in a 2006 article. A good read; I recommend it.

Doug is a great guy -- pursues what he's interested in, be it homebrew, viniculture, skateboarding (he once rode the length of the C&O Canal on a self-made board -- read about it in this New York Times Magazine article), or archaeology.

Doug attended my "Walkingtown, DC" walking tour of DC's geologic history, and brought along a few odd rocks for me to identify. At the end of the tour, he invited me over to see his museum. Yesterday, I finally got the chance to do that. We cracked open a couple bottles of Dogfish Head 60-minute IPA and started browsing his collection of found prehistoric objects. Doug was very interested in my analysis of rock types (apparently archaeologists use a different set of terminology for describing what rock types projectile points are made out of).

On his own property and in neighboring areas of the Palisades, Doug has found hundreds and hundreds of objects, many of them beautifully worked arrowheads of flint, quartzite, and rhyolite. There are also some oddballs that don't fit with the human prehistory theme: a 1791 coin bearing the image of Louis XVI, crystals of amethyst and gypsum, old glass bottles, rounded river cobbles, and anything else that caught his attention. One of the most astounding things I saw yesterday was a huge woolly mammoth tooth. Doug told me a friend of his found it in the Potomac River while canoing (I think he said near Seneca Creek, but that was a beer and a half in, so maybe I've got that wrong). But there it was, a fully ridged mammoth molar; unmistakable. I hadn't heard of previous mammoth finds in our area, but I guess it's not surprising they were here.

Anyhow, I had a great time, and I recommend that everyone in the DC area make an appointment with Doug to go check out his collection and support his project.

Labels: cenozoic, dc, history, mesozoic, museums, piedmont, tourism

This one's a good one to assign to Historical Geology students who don't have time to read The Map That Changed The World. It's part of the series "On the Shoulders of Giants" by NASA's Earth Observatory: William Smith.

I love the way these pages are laid out: a single column of text with illustrations of different sizes and dimensions interspersed with the content. It's like a Dorling Kindersley book. NASA must have some good web designers on the payroll.

Labels: books, fossils, geologists, history, stratigraphy

Here's a photo of one of the cool things that my Honors students and I got to see on our recent trip up to Buffalo, New York (for the northeastern section meeting of GSA ):

That's an original, signed edition of the William Smith geologic map, brought to the meeting courtesy of the Buffalo Library. It is one of only two in the United States; the other is at the Library of Congress. The map found a home in Buffalo (of all places!) thanks to Chauncey Hamlin, the head of the Buffalo Museum of Science (then called the Buffalo Society of Natural Science) from 1920 to 1948. During his tenure, he assembled a collection of first editions of many seminal scientific works. First editions of Charles Lyell's Principles of Geology and Herbert Hoover's* translation of Agricola's De Re Metallica were also on display at the conference.

* Yes, that Herbert Hoover, at least according to Wikipedia.

Labels: geology, history, maps, meetings, nova

It's funny how one thing leads to another. In promoting our Climate Change Symposium on Friday, I wrote to Cerphe (pronounced "Surf"), probably the best DJ in the world, who's on air in the afternoons on 94.7 The Globe, our DC-area "world-class rock" station that also features a green message. Cerphe wrote back, saying he'd get some mentions on the air this week, and also mentioned that his wife has a small business building green homes. I noticed that the business is headquartered in Bentonville, Virginia, out in the Shenandoah Valley between Massanutten Mountain and the Blue Ridge. And it occurred to me that I've looked at a bentonite layer out there in the Valley (see photo), not too far away from Bentonville. Bentonite is a common clay mineral that in stratigraphic layers is usually interpreted as weathered volcanic ash. (The one pictured above is possibly the "Big Bentonite" that accompanied the onset of the Ordovician Taconian Orogeny in eastern North America.) Could it be that bentonite is named for Bentonville, Virginia? Well, Wikipedia tells me that "The absorbent clay was given the name bentonite by an American geologist sometime after its discovery in about 1890 ...after the Benton Formation in Montana's Rock Creek area." So that took me to the entry on Fort Benton, Montana, which was named for the first 5-term U.S. Senator, Thomas Hart Benton. He was an advocate of westward expansion by the United States, the idea that later was dubbed "Manifest Destiny." So: as near as I can follow, bentonite is a mineral named for a place, which is in turn named for a man. What this has to do with world-class rock and climate change is anybody's guess.

Labels: appalachians, history, montana, volcano