Friday, November 13, 2009
Tuesday, November 10, 2009
Northwest Branch GeoCache
Labels: geomorphology, maryland, piedmont, rivers, websites
Thursday, October 1, 2009
How to read a seismic cross section
So here's how this works: the top image is a map. It gives you a "bird's eye" perspective on earthquake locations at the subduction zone near Samoa. It shows you the epicenters (location on the earth's surface above a quake's actual location, called its "focus" or "hypocenter") of many earthquakes, along with Tuesday's big quake, shown with a star. The thick red line is the position of the trench, a bathymetric expression of the subduction zone. The epicenters are color-coded for their depth. Orange and yellow are shallow; green and blue are medium depth; and purple and red are the deepest. Notice that they make a sort of "rainbow" pattern, with the shallowest quakes in the east, and the deepest quakes in the west. This is "looking down" on the subducting slab: it's like we're able to "see" the subducting slab as it descends into the mantle.
The lower image is the cross-section. It gives you a "gopher's eye" perspective on the same data. A cross section is drawn along the line A-A' on the map. This is conceptually slicing the Earth open along that line, then removing half, and looking sideways at the remaining half. Note that the A-A' line is now along the top of the figure, representing the surface of the earth. Along the horizontal axis is horizontal distance, measured in kilometers. Along the vertical axis is depth, also measured in kilometers. The two axes are not drawn to exactly the same scale, but pretty close. In other words, 100 km of horizontal distance is approximately equal to 100 km of vertical distance (depth). The same data are plotted, or at least the subset of the map's data which happen to fall on that particular line, A-A'.
With this new perspective, a side-view, what do we see? Well, there's the star, which shows the depth of the quake that triggered all this discussion, and a whole bunch of other (historical) earthquakes. Now, instead of the epicenter being plotted, we're getting a more robust sense of the hypocenter (or focus). Note that the earthquakes are being generated in a big swath, starting at the surface in the northeast, and dipping down deeper and deeper to the southwest. This line of seismic activity reflects the jerking passage of the subducted slab of oceanic lithosphere. As it plunges down, it generates lots of shaking. This zone of seismicity was first described (independently) by two scientists, Kiyoo Wadati and Hugo Benioff: in their honor, it is referred to as the Wadati-Benioff zone. (Wikipedia has more) Their realization is our gain: we can "see" the subducted plate diving at an angle of 30 to 40 degrees. That's what's so cool about this:
Something that no human will ever directly observe is "visible" to us because we can pinpoint the three-dimensional location of thousands of earthquakes. These bumps and jolts reveal the position of the bumper and jolter: the subducting plate!
Labels: analogies, art, earthquakes, plate tectonics, websites
Wednesday, September 30, 2009
Awesome: Samoa subduction cross-section
The star gives the location of yesterday's temblor some regional context. This is a super-cool visualization of a subduction zone (in this case, the Pacific Plate subducting beneath the Indo-Australian Plate). I'll be using this image in my upcoming "earthquakes" lecture in Physical Geology. What a beautiful way of visualizing the plunge of a slab of oceanic lithosphere!
Labels: art, earthquakes, plate tectonics, websites
Thursday, September 24, 2009
National Geologic Map Database

You can then close the little "About" information tab in the lower right:

Next, grab the screen and scroll to an area that you're interested in:

Double-click or use the "zoom" lever at upper left to zoom in:

Open the "Map Unit Info" tab to select individual map units and learn more about them:

After you do that, clicking anywhere in the map will bring up information about the rock units generally found in that area:

If you need more information, hover over the rock unit name in the "Map Unit Info" tab:

Close the "Map Unit Info" tab and open the "Map List" tab to get a list of all the USGS geologic maps available in your field of view:

Click on one of them to open up a red "footprint" on the map showing the area it covers:

An additional window will pop up with information about the map. Click on the number "2" in this new window to open the map itself:

It opens in a new tab, and is initially quite zoomed-out:

But you can zoom in, of course:

In fact, you can zoom in really far, until you start seeing pixels:

There are some design flaws in the interface, but overall, I think I'm willing to overlook them so I can get access to this sort of information. It strikes me as very, very useful: a rich dataset, waiting to be mined.
Thursday, August 20, 2009
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
Tuesday, August 11, 2009
Some more recommendations
Weather vs. climate (Surprising Science, a Smithsonian blog)
The new Wooster Geologists blog, featuring some awesome imagery of the Canadian Rockies.
Some advice about finding the right geology grad program for you (from Christie at the Cape)
Labels: climate change, global warming, politics, websites
Monday, August 10, 2009
Virtual samples
Here's my favorite... Or maybe this one? ...Or potentially this one? No, no: definitely this one.
Actually, this is pretty cool too. Sigh... too many to choose from. Too hard to pick just one fave...
Hat tip to Lee Allison!
Good stuff from the past week
The geography of tapirs, from the Why Evolution Is True blog.
The declining emphasis on literacy in our society, from Alternet.
Women geoscientists who read and/or write blogs: complete this survey!, from Kim.
Outcropedia, a new web project to catalog and share key outcrops.
Climate change graph jam, from Tamino. (With follow-ups from Lockwood)
Skeptics & athiests visit the Creation Museum. (ABC News)
Labels: blogs, evolution, graphics, humor, maps, politics, websites
Friday, July 31, 2009
Some other Rockies projects
Ringing Rocks (Bob)
Lewis & Clark Caverns (Charlie)
Gros Ventre Landslide (Chris)
Monday, June 15, 2009
Wedge accreted
Labels: blogs, geologic time, geology, websites
Wednesday, June 10, 2009
Flash animations in geology
Hat tip to Pete Berquist for this link!
Saturday, June 6, 2009
HOME
An impressive talk, and the film he alludes to was released yesterday, for free.
The movie HOME is available now, for free download. Enjoy!
Labels: environmental, meetings, movies, websites
Monday, June 1, 2009
Not all scientists study human health...
Labels: geologists, science and society, websites
Wednesday, May 27, 2009
Climate denial crock of the week
Labels: climate change, websites
Sunday, May 17, 2009
Wolfram Alpha
You have got to check this out. (Wait for it to load, then watch the introductory video.) This appears to be a vision of the future for folks who are interested in data.
Hat tip to Babak for this alert.
Monday, April 20, 2009
Lowenstern interview on YouTube
Part I:
Part II:
Part III:
Thanks Stef!
Labels: volcano, websites, yellowstone
Tuesday, April 14, 2009
NASA Earth image of the decade
My personal choice? I'll bet you think it looks familiar... It's this one:
Labels: contest, satellite imagery, websites
Sunday, April 12, 2009
Cool cache of photos
Thursday, April 2, 2009
Saturday, March 7, 2009
GSW on Wikipedia
Saturday, January 31, 2009
Clever cover
Whoever designed that deserves a bonus. Pretty clever.
Labels: art, blogs, books, climate change, global warming, websites
Friday, January 16, 2009
Distinguishing felsic from mafic (from space!)
The image, originally from NASA's Earth Observatory (one of the finest websites I know of for those interested in Earth science), shows a collection of volcanoes in the western Arabian Peninsula. A large version of the image (unlabeled) is here.
The most spectacular thing about this image is the color contrast between the volcanoes on the left versus the volcanoes on the right. This spectacular contrast is indicative of the rock types involved in each volcano. On the left, felsic lava was erupting, which cooled into the extrusive rock rhyolite. On the right, mafic lava was erupting, which cooled into the extrusive rock basalt. Mafic igneous rocks like basalt have a higher proportion of the elements iron, magnesium, and calcium as compared to elements like silicon, potassium, and sodium. Felsic igneous rocks are, in a sense, distillates of mafic source rocks: they are made of minerals that are more easily melted.
Also worth noting is the way the basalt overlaps the rhyolite between Jabal Bayda' and Jabal Abyad tells us that the rhyolite came first, and the basalt came second, an example of relative dating. And these insights can be gleaned from space... or more accurately, from our computer screens, depicting an image from space. That's pretty incredible, when you think about it.
FYI, here's what NASA's William Stefanov wrote as the caption for this exceptional image:
The western half of the Arabian Peninsula contains not only large expanses of sand and gravel, but extensive lava fields known as haraat (harrat for a named field). One such field is the 14,000-square-kilometer Harrat Khaybar, located approximately 137 kilometers to the northeast of the city of Al Madinah (Medina). The volcanic field was formed by eruptions along a 100-kilometer, north-south vent system over the past 5 million years. The most recent recorded eruption took place between 600-700 AD.
Harrat Khaybar contains a wide range of volcanic rock types and spectacular landforms, several of which are represented in this astronaut photograph. Jabal ("mountain" in Arabic) al Qidr is built from several generations of dark, fluid basalt lava flows. Jabal Abyad, in the center of the image, was formed from a more viscous, silica-rich lava classified as a rhyolite. While the 322-meter high Jabal al Qidr exhibits the textbook cone shape of a stratovolcano, Jabal Abyad is a lava dome; a rounded mass of thicker, more solidified lava flows. To the west (image top center) is the impressive Jabal Bayda'. This symmetric structure is a tuff cone, formed by eruption of lava in the presence of water. The combination produces wet, sticky pyroclastic deposits that can build a steep cone structure, particularly if the deposits consolidate quickly.
White deposits visible in the crater of Jabal Bayda' and two other locations to the south are sand and silt that accumulate in shallow, protected depressions. The tuff cones in the Harrat Khaybar suggest that the local climate was much wetter during some periods of volcanic activity. Today, however, the regional climate is hyperarid - little to no yearly precipitation - leading to an almost total lack of vegetation.
Labels: basalt, blogs, igneous, middle east, satellite imagery, volcano, websites
Sunday, December 21, 2008
WIRED covers AGU
Thursday, December 18, 2008
Props
Tuesday, December 9, 2008
Regatorgnition
I've never heard of Regator before. Anybody else in the geoblogosphere getting such a note? There are several of us featured on their website under "geology": Lounge of the Lab Lemming, Hypo-theses, Harmonic Tremors, Andrew's Geology Blog at About.com, Olelog, Looking for Detachment, All My Faults Are Stress-Related, Magma Cum Laude, Oakland Geology, Arizona Geology, and Highly Allochthonous. (my apologies if I missed anyone)
Labels: blogs, geologists, websites
Monday, December 8, 2008
Raw Bolivian landscapes on Oddee
Labels: salt, south america, websites
Friday, December 5, 2008
Recommendation: "How sinkholes work"
Thursday, November 6, 2008
Marli Miller's geology photographs
A couple of weeks ago, I mentioned AGI's Image Bank, and to illustrate it I picked three photos by Marli Miller (at the University of Oregon). Dr. Miller has written me and shared a link to a website she has put together to share high-resolution images of geological features and processes. Educators have permission to download the photos for teaching (non-commercial) use. And everyone can benefit from visiting to check out the many gorgeous images there.
Election maps
Four years ago, this website gave me some solace in looking at the breakdown between "red" and "blue" states. Now the author, Mark Newman, has performed some similar cartography on the 2008 presidential election results. Monday, October 20, 2008
Meteorites in Ordovician limestones!
Sunday, October 19, 2008
Gray rock quiz
Labels: igneous, metamorphism, minerals, nova, sediment, websites
Saturday, October 18, 2008
AGI Image Bank
Wednesday, October 1, 2008
Cinematic maps
Maintained by the Digital Scholarship Lab at the University of Richmond (Virginia), the website makes us of so-called "cinematic maps" which show how geopolitical data have changed over time for the lower 48 United States.
The different maps tell stories over time; I think it's a cool display of interesting information. However, a major omission is the exclusion of Alaska and Hawaii as contributing U.S. states. Check it out; let me know what you think.
Thanks Judith G. for alerting me to it!
Friday, August 15, 2008
Three-dimensional trilobite images
With undergraduate student Martha Buck, he's taken pyritized trilobite fossils from the upper Ordovician Frankfort Shale ("Beecher's Trilobite Beds") near Rome, New York, and X-rayed them. A series of X-ray images taken at different angles have been spliced together into a movie, which gives a real sense of the three-dimensional nature of the fossil, as well as insight into the finer details of its anatomy like legs and antennae, which don't often fossilize:
This is Triarthrus eatoni. You can replay the movie by refreshing the page on your Internet browser. The full suite of images is available on this page. Check it out!
Labels: fossils, ordovician, websites
Monday, August 11, 2008
Illustration page updated
Saturday, July 19, 2008
Friday, May 16, 2008
Volcano monitoring: last night's PGS meeting
The meeting was held at Fort Meyer Officer's Club. It's on a military base adjacent to Arlington National Cemetery, and before entering, my Prius had to be searched for bombs (as did all other civilian vehicles). The Officer's Club was about what you would expect, I guess -- kind of 1950's decor, elegant once. I noticed they had compact fluorescent light bulbs in all the sockets, which pleased me. PGS meetings consist of: (1) beer downstairs in the lounge, (2) dinner upstairs in the "Campaign Room," (3) business details, and (4) a talk by a guest speaker.
Last night's speaker was Bill Burton, from the USGS's volcano hazards and monitoring program. Bill's office will be launching a comprehensive new volcano website later this year, and he gave us a brief preview of its features in last night's talk. If you'd like a look for yourself, they have a beta version of the site online now.
I was struck by two things about Bill's talk. First, that the volcanoes that the USGS has fully equipped with monitoring instruments (high-precision GPS, seismographs, etc.) provide a wealth of information which makes it relatively easy (relative to say, earthquakes) to predict eruptions. We've learned enough that we can use subtle signals to issue eruption watches and warnings, for both people on the ground and planes in the air.
At the end of the talk, I asked Bill about this: "How much more money would your office need to outfit the under-instrumented volcanoes to the level you think they need?" Bill estimated $80 million, both for installation and the constant upkeep these instruments require. This morning on the drive into work, I heard that the new farm bill has $450 million set aside for Chesapeake Bay environmental work, so while $80 million seems like a lot to me, I guess it's not all that much in the grand scheme of things. In a post this morning, Nicholas at The Critical Zone examined this issue of huge numbers, and all the science that could get done with that money.
Monday, May 5, 2008
Tag Crowd for my C&O Canal geology book
Saturday, April 26, 2008
Darwin online
Also, NPR did a piece on the material being made web-accessible.
Monday, April 14, 2008
World Mapper
For instance, countries scaled to their population sizes:
Or here's the number of preventable deaths per country:
Build your own, or let me know if you find any other interesting ones...
Thanks to Anastassia for tipping me off on this one!
Sunday, April 6, 2008
Northern Ireland geology website (BBC)
Anyhow, Alan clued me in to a new series from the BBC called "Blueprint," wherein they examine the natural history of the Emerald Isle. There's a cool interactive aspect to the website where you get a map of Ireland and a choice between "Plants/Animals," "Humans," and "Land." Choose "Land" and then select what you want to learn more about. Then you get a series of images, conversations, or videos about different aspects of Northern Ireland's geologic history. It's pretty cool -- there's a really enthusiastic dude (William Crawley) talking about the eruption of the Giant's Causeway, and also examinations of "the Chalk," graptolites, and granite gneiss. They even mention the Iapetus Ocean! (Which was a big focus of the field trip I led today!)
Labels: chalk, giants causeway, northern ireland, websites
Saturday, March 15, 2008
Unscrew yourself

What would it look like if Napolean Dynamite designed a website to promote energy conservation by switching out lightbulbs? Maybe something like the "Unscrew America" website. The navigation is a bit of a head-spinner, though. Take your Dramamine before you start moving that mouse around.Labels: energy, environmental, websites
Friday, February 29, 2008
Weirdness with a geologic name
Reading David Byrne's blog last week, I was alerted to the existence of The Museum of Jurassic Technology in Los Angeles. When I went to this museum's website, I found a phantasmagoria of odd objects and pseudoscientific farce. It's not supposed to be real; it's supposed to be art. But... why "Jurassic?" Like a lot of McSweeney's works, it seems a little too clever for me to "get." Though not a geologist, Byrne seemed similarly perplexed: "the mixture of the real ... and the imaginary... is a bit of a head twister at first."
Wednesday, February 27, 2008
Svalbard's sea monster
National Geographic has an article online about a cool new fossil from Spitsbergen, Svalbard (the Arctic island achipelago belonging to Norway). It's a plesiosaur, a marine reptile from the Jurassic period of geologic time. The front flipper is almost ten feet (3 m) long! The online article includes a picture gallery (the site, the fossils, and National Geographic's beautiful reconstructions).
Wednesday, February 13, 2008
Google "My Maps"
It occurs to me that My Maps might be a good way to share geologic knowledge about outcrop locations. One thing that I found frustrating and limiting in my first few years of teaching was that there was no good single source to go to find out about relevant outcrops. It took time and experience to find out where the cool rocks were. Is it a good idea to put this information online in a publicly-accessible format so beginning instructors and interested students/amateurs can visit interesting outcrops? (I sure would have appreciated it four years ago!) Or does that run the risk of letting rockhounds and less-than-ethical geovandals onto previously-secret locations? Is there a benefit to the ancient barriers in outcrop-information flow? Is it better to pass this information on from wise elder to trusted neophyte?
Friday, January 25, 2008
New article up at Geotimes
Labels: northern ireland, websites
Sunday, January 20, 2008
Geology of Maine
The Maine Geological Survey maintains a terrific website with lots of information about the state's umpteen gazillion geological locales.I feel like you could run a virtual field trip to Maine with the wealth of quality information and and images they have on this site. It's all well illustrated with lots of photos of structures and geologic contacts.
Learn more about the granite dikes at Pemaquid Point Lighthouse.
Or learn about where to find pillow basalts.
Or check out the giant purple crystals at Mount Apatite.
Or check out the distinctive dark feldspars of Maine's only "shonkinite".
It's all there, plus much, much more! Enjoy.
Wednesday, January 9, 2008
iTunes U?
I like this idea, but wonder how much time it's going to take. In general, I am super-duper excited over the advent of increased sharing online, and the decline of barriers to sharing. One of my pet peeves has been academic journals. Many are published by huge publishing companies like Elsevier, who make money off of them. For many years, scientists (and other scholars) who wanted to publish their research were forced to give up the copyright to their work and turn it over to one of these companies. Other scientists (or other scholars) who wanted to read about the research then had to pay OUTRAGEOUS subscription fees for these journals. I'm talking thousands of dollars a year -- far beyond the means of anyone who doesn't have a massive academic bureaucracy backing them up. To me, this seems massively unjust. It's the scientists who produce and consume the research; and publishing companies appear to make crazy profits off of all that stressful labor by others. ...Reminds me of slavery!
However, the Internet has the potential to change all that. With the net, anyone can publish their research online, and someone else on the other side of the world can access it 2 seconds later. With this, of course, comes the potential for lousy scholarship and fakery in research. At least that's the line touted by Elsevier and their ilk. Peer review is still essential, and it's going to be cool to see which journals get on board with the new reality. One I checked out recently is PLoS One. (They had a research article on really cool jellyfish fossils from the Cambrian, which is how I found out about them.) Somewhat more basic is the Journal of the Virtual Explorer, where my thesis advisor and some colleagues published an article (about kink banding) in 2004.
And while you're talking about the distribution of online information, it would be remiss not to mention Wikipedia. Wikipedia is HUGE among my students. I frequently use it myself as a handy reference. But handy doesn't mean accurate. Because anyone can edit the entries on Wikipedia, it's not guaranteed to be peer reviewed. A competitor, Citizendium, hopes to out-wiki Wikipedia with fully-refereed articles written by identifiable authors. WIRED explored their competing styles in their recent "Geekipedia."
More information about the iTunes U / online lecture phenomenon is available in a Washington Post article from the end of December.
Historical paleontology art at the Smithsonian
The Smithsonian's department of paleobiology has a webpage devoted to displaying some art that was used in some old scientific papers on fossils. There's a beautiful variety of images there, like this frontal view of a Triceratops skull that was used to prepare a lithograph, which then appeared in a paper by legendary paleontologist Othniel Charles Marsh (archnemesis of Edward Drinker Cope). Check out the full variety of art here.Labels: art, fossils, smithsonian, websites
Monday, December 24, 2007
Astronomy picture of the day
The "Astronomy Picture of the Day" web site showcases a different image of the Cosmos every day. Nice! I've got it on my RSS feed, so everyday when I log into my Google account, I've got an image like this one greeting me. Clicking on the image takes you to a larger version and a more detailed description of the pic.
















