May 21, 2013 by Chuck Bailey
Remember the Alberene Dream Team from the summer of 2011? This talented group of undergraduates poured themselves into research projects aimed at understanding the geology of the eastern Blue Ridge Mountains that summer and continued their work as part of their senior research during the academic year. Alex Johnson, the youngest member of the Alberene Dream Team, graduated from the College last Sunday (Andrea, Kevin, and Molly were in the class of 2012). The week before landing his diploma Alex helped lead a raucous field review across the Alberene quadrangle.
The U.S. Geological Survey funded our research and as such we have a responsibility to get this geologic map and the attendant data published so the results are accessible to the wider world. A necessary step towards publishing a geologic map is the field review. We invited geologists from the U.S. Geological Survey, the Virginia Division of Geology and Mineral Resources, academics, and other interested individuals to join us for a day in the field and asked for their critical comments on the map and our geologic interpretations.
We visited 10 outcrops: from roadside exposures of the basement complex, to an old soapstone quarry, to a magnificent outcrop of metabasalt with deformed pillows along the Hardware River. Alex Johnson and John Hollis framed most of the discussion with Professor Brent Owens and I chiming in on occasion. We argued our case and learned from other geologists.
This summer we’ll do a bit of targeted fieldwork to better resolve some problem spots on the map and make revisions based on the comments we received during the field review. Once that is complete we’ll submit it for yet another review. It is a long road to publication, but an important road to travel nonetheless.
April 12, 2013 by Chuck Bailey
Last week the William & Mary Geology department played host to a group of international geoscientists that descended upon Williamsburg from Japan and Oman. They were at William & Mary to attend the 3rd Critchfield Conference which focused on the Indian Ocean Basin: Navigating the 21st Century Marine Silk Road. Prior to their conference duties, we had the good fortune to rope them into delivering seminars in the Geology department and meeting with geology students.
Professor Toshio Mizuta, the former director of the International Center for Research and Education on Mineral and Energy Resources (ICREMER) at Akita University, Japan discussed his research on Kuroko-type massive sulfide deposits. Professor Takashi Uchida, Professor of Earth Science and Technology at Akita University, presented an overview talk on non-conventional energy resources such as gas hydrates. Collectively, their talks highlighted some new frontiers of mineral and energy exploration. As a mineral resource-limited island nation, Japan has focused much effort on seafloor mapping in a quest for discovering new resources.
Professor Abdullah Al-Ghafri of the University of Niwza, Oman delivered a seminar to a packed house that focused on his research on Aflaj, an ancient water management system used in arid regions through the world. Later this year I will be starting a geologic research project in Oman and Dr. Al-Ghafri will play a key role in helping me build connections with other Omani scientists. There were also representatives from the Oman embassy in Washington, D.C. and the Sultan Qaboos Cultural Center in attendance.
Geology is a science in which both time and place are important, and as such the Geology Department is well positioned to forge ahead into the realm of international education and research. In the not-so-distant future, we aim to run a geology and environmental field study program in Oman. A joint field trip with Japanese faculty and students to Alaska to explore base-metal deposits is also a possibility. Exciting times ahead.
November 26, 2012 by Chuck Bailey
Here is the opening question from the last problem set in my Earth’s Environmental Systems course (GEOL 110).
I thought my clues were amply generous. The photograph is of Palace Square in St. Petersburg, Russia. Google Earth is a great tool for checking out this scene and determining the latitude and longitude (59.9˚ N, 30.3˚ E). Inspecting the scene in Google Earth makes it clear that the photographer was looking to the South across Palace Square from a window in the Hermitage Museum.
That was the prelude. The 2nd part of the question asks.
Mike Blum, W&M Academic Technology Specialist Extraordinaire, took the photograph. His wife, Professor of Modern Languages Bella Ginzbursky-Blum, often directs William & Mary’s summer study program in St. Petersburg. I first saw the photo framed on the wall at their house and was captivated by the scene. When I asked to use the photo I told them NOT to tell me the date and time at which the picture was taken—if I’m going to ask W&M students to figure that out I’d better be able to do the same.
So just how do we figure out the date and time when the photograph was taken? The key lies in the shadow cast by the massive Alexander’s Column at the center of the square. Alexander’s Column is a large monument erected in the early 1830’s to celebrate Russia’s victory over Napoleon’s armies. It stands 47.5 meters tall and is reputably the world’s tallest column made from a monolithic block of rock (granite, in this case).
By making a triangle between the column and the shadow we can determine the solar elevation angle (Ψ) by either measuring it directly on the photo with a protractor (my students say that’s old school because they last used protractors in elementary school) or by using a dash of trigonometry. The solar elevation angle at the moment the photo was taken is 47˚.
The solar declination (δs) follows an annual path that crosses the equator at the equinoxes and reaches 23.45˚ N (Tropic of Cancer) on June 20th/21st and 23.45˚ S (Tropic of Capricorn) on December 21st/22nd. This path is graphically illustrated by the analemma, that strange figure-8 shape lurking in the Pacific Ocean on many globes.
Recall that St. Petersburg is located at 59.9˚ N latitude and we measured a solar elevation angle (Ψ) of 47˚ at Alexander’s Column. For the sun to reach a solar elevation angle of 47˚ in St. Petersburg the solar declination must be at 17˚ N or further north (Ψ = 90˚ – [Latitude of St. Petersburg – δs]), reading the analemma reveals that the solar declination is ≥17˚ N from May 9th until August 4th. At any other time of the year the sun never gets high enough in the sky to reach a solar elevation angle of 47˚ in St. Petersburg. Ok, we’ve narrowed the range of dates to just under three months, but we can do better.
The azimuth of the column’s shadow is pointing to the northeast (an azimuth of 41˚, actually), which means the sun is located to the southwest (an azimuth of 221˚ which is 180˚ from the shadow). Local noon occurs when the sun passes due south of a particular location (for mid-latitude locations in the northern hemisphere) and the sun tracks to the southwest in the afternoon—clearly this photo was taken in the mid-afternoon. The sun reaches its zenith at local noon and then the solar elevation angle gets progressively lower throughout the afternoon. Put another way, if the solar elevation angle in the afternoon is 47˚, it’d be even higher at local noon.
There is an explicit relationship between the solar elevation angle (Ψ) and the azimuth angle of the sun (α) that can be determined for any latitude and time. It’s given by two cumbersome trigonometric formulas (not shown), but if one’s latitude and the solar declination (date) are known we can calculate when the sun rises and sets and its position throughout the day.
For our picture of Palace Square, we know the solar elevation angle (Ψ) at that moment = 47˚ and the azimuth angle of the sun (α) = 221˚. There are only two days of the year that yield that combination of elevation angle and azimuth—June 3rd or July 11th at 14:54 (2:54 p.m.)*. I suspect it’s the earlier date—June 3rd. Look closely at the people in square: they are bundled up, suggesting it is a cool day in St. Petersburg, I’d expect cool weather in early June more so than July.
I forwarded my answer to Mike and Bella: Mike responded “Not bad. June 3, 2004 at 2:49 p.m.”. I was off by 5 minutes, but this is where the equation of time and the analemma come to the rescue.
The north-south component of the analemma illustrates the solar declination throughout the year, but the east-west component illustrates the equation of time and whether the sun is ahead or behind clock time. Because the Earth’s orbital path around the sun is elliptical, and the Earth’s rotational axis is tilted relative to the ecliptic plane, there is a difference between mean solar time and apparent solar time that varies regularly throughout the year. On June 3rd the sun is 3 minutes ahead of clock time—so my final answer is 14:51.
Did I only give credit for June 3rd at 14:51 local time? No, full credit answers went to anybody that put the date between June 1st and July 15th and called it mid-afternoon. Collectively, the class did fine. As I’ve mentioned in earlier posts, I want students to be able to think spatially: questions like this are meant to get spatial thinking skills into high gear.
Why pose a question like this? Who, especially in a first-level non-majors course, is likely to employ this type of analysis (photogrammetry) somewhere down the road? Very few I expect, although photogrammetric analysis is regularly employed by intelligence agencies (how do you think the Russian missile sites in Cuba were sussed out back in 1962?) and has been utilized to offer insight on controversies such as who first reached the North Pole. But more importantly, I want William & Mary students to use their own observations to understand the world. These types of questions might appear to come from ‘left-field’, but neatly demonstrate how much can be discovered about the Earth’s environmental systems from close inspection of everyday scenes.
*St. Petersburg is on Moscow time.
October 26, 2012 by Chuck Bailey
Water gaps are intriguing and iconic landforms that have long drawn humans to them. We are all familiar with streams and rivers flowing in valleys; a water gap is dramatically different- it’s a place where a river cuts though a ridge or mountain range. Thomas Jefferson discusses the Potomac River water gap in his Notes on the State of Virginia (1785), declaring in an often-quoted passage: “This scene is worth a voyage across the Atlantic.”
For me, the prose that comes earlier in the same paragraph is even more vivid.
The passage of the Patowmac through the Blue ridge is perhaps one of the most stupendous scenes in nature. You stand on a very high point of land. On your right comes up the Shenandoah, having ranged along the foot of the mountain an hundred miles to seek a vent. On your left approaches the Patowmac, in quest of a passage also. In the moment of their junction they rush together against the mountain, rend it asunder, and pass off to the sea.
The Appalachian Mountains are flush with water gaps (e.g. Delaware water gap, Cumberland gap), but water gaps are common features in many mountain ranges worldwide. Water gaps are important as they typically form a route of conveyance through steep and mountainous country and they’ve long been utilized as routes for wagon trails, railroads, and highways. The Potomac River water gap through the Blue Ridge Mountains has been a pivotal place in American history since Colonial times.
Southwest from Harpers Ferry the Blue Ridge Mountains form an unbroken topographic barrier for 240 km (150 miles). The next water gap is near Lexington, Virginia, where the James River has carved a 10-km (6 mile) gorge through the Blue Ridge, a range with peaks over 1,200 meters (4,000 feet) in elevation. This is an impressive gap- see for yourself by playing this Google Earth tour through the James River water gap (kmz).
How can a stream cut a path across a mountain ridge or range that lies in its course?
At the Potomac River water gap Jefferson opined:
…this scene hurries our senses into the opinion, that this earth has been created in time, that the mountains were formed first, that the rivers began to flow afterwards, that in this place particularly they have been dammed up by the Blue ridge of mountains, and have formed an ocean which filled the whole valley; that continuing to rise they have at length broken over at this spot, and have torn the mountain down from its summit to its base.
TJ is certainly entitled to his opinion, but he’s not the only one to wax poetic on this topic.
For another take on the landscape consider John Denver’s famous lyrics in the song Country Roads:
Almost heaven, West Virginia
Blue Ridge Mountains, Shenandoah River
Life is old there, older than the trees
Younger than the mountains, blowing like a breeze
So according to John Denver the trees are younger than the life, and both the trees and the life are younger than the mountains (i.e. old mountains).
But what about the Shenandoah River? Is the Shenandoah River older or younger than the Blue Ridge Mountains? In Jefferson’s landscape model, the mountains formed first, creating a topographic barrier that was later breached by the river carving out a water gap. But there is another possibility: what if the rivers were there first and the mountains formed later? In this model, the rivers are older and maintain their courses while the mountains are uplifted. These rivers would be antecedent streams that pre-date the current topography through which they flow.
What do you think? Are the Blue Ridge Mountains older than the rivers (Potomac/Shenandoah and James systems) that flow through these impressive water gaps? Or do these rivers pre-date the formation of the Blue Ridge and Appalachian Mountains?
Let me know and we’ll return to this question in a follow up post.
October 4, 2012 by Chuck Bailey
My Geology 110 course, Earth’s Environmental Systems, is a big class. 195 students are enrolled and we meet for 50 minutes at 9 a.m. on Monday, Wednesday, and Friday. A big part of my job is to keep these 195 students engaged during our class meetings. This semester I am using LectureTools, a web-based software tool, that allows students to follow my presentations, ask questions, answer questions, and solve problems in class using their laptops, iPads, and smart phones. I get real time feedback from students: “Chuck, that last slide confused me”, “Chuck, please don’t put that question on the exam!”, etc. I ask questions and we can collectively see just how well they’ve done. Based on the answers I can change the pace or direction of the lecture. LectureTools has much promise. Thus far, the response from students ranges from mildly positive to robustly jubilant.
Understanding spatial relations on planet Earth is at the heart of understanding the Earth’s Environmental Systems. For many students, sorting out spatial relations is a challenge. We’ve considered solar elevation angles and insolation which leads to thinking about the Earth’s seasons and its axial tilt. Last Friday, I put up this satellite image of the Earth and asked:
On what day was this photo taken?
Notice the Earth is illuminated from its far northern reaches (Greenland) all the way to the Southern Ocean and Antarctica. The picture was taken by the Meteosat 9 satellite on September 22nd—the autumnal equinox (for the northern hemisphere). I expected it would be easy to tell that it was one of the equinoxes. But which equinox? The abundant sea ice in the Southern Ocean means that the region is emerging from its winter (the northern hemisphere’s summer). The results from my class were far different than my expectation. 61 of the students got the answer correct (that’s 37%), but 63% of the responses were incorrect and more people chose the summer solstice over the spring equinox. Yikes, we have a problem.
Having the results for everybody to see, immediately after students have answered a question is a great innovation. I then talked the class through the observations required to know that the image was taken on the autumnal equinox.
On Monday morning I tried a similar question on my charges.
Indeed this photo was obtained on the December solstice as evidenced by the illuminated region in the Antarctic and the darkness in the northern latitudes. A majority of the class got the question correct, but a sizable fraction was still confused. Better results, but not what I was hoping for. I followed this question with an annotated image illustrating a tilted Earth and a labeled equator. It’s all so easy when things are labeled!
On Wednesday I threw the class a related question and assumed that the third time would be the charm. LectureTools enables me to ask image questions in which students click on a map or an illustration to answer a question. My question concerned the current location of the subsolar point at 9:30 a.m. (EDT) on Wednesday, October 3rd. The subsolar point is the place on the planet where the Sun is directly overhead (solar elevation angle = 90˚).
The autumnal equinox had passed 10 days earlier, thus the subsolar point is a few degrees south of the equator. It was mid-morning in Williamsburg and in Greenwich, England (located on the Prime Meridian) it was mid-afternoon, thus noon (the time when the Sun reaches its zenith) was to the east of Williamsburg and to the west of Greenwich. The subsolar point at that moment was in the Atlantic Ocean to the east of Brazil.
A sizable fraction of the class placed the subsolar point in the Atlantic Ocean to the east of Brazil—nice work! Unfortunately, others placed the subsolar point in the northern hemisphere or worse yet, far to the north of the Tropic of Cancer (that never happens!). Not good news. But this in-class assessment paints a clear picture of what students grasp and, more importantly, don’t grasp. Back to the drawing board? I’ve got to figure out how best to help students learn these concepts and master spatial relations. I am a believer in “Practice Makes Perfect”, we shall see what the fourth try brings!
September 26, 2012 by Chuck Bailey
The James River’s basin spans much of Virginia. Its headwaters start amongst the high ridges of the Allegheny Mountains, and the river system covers some 700 kilometers (~400 miles) before debouching into the Chesapeake Bay at Hampton Roads. The river crosses four of Virginia’s five geologic provinces and exposes a wide array of rocks. Outcrops in and along the James provide key exposures for geologic research, and I’ve written about our numerous adventures on the river before. It is also an ideal watershed for reflecting upon hydrologic systems.
Last week a weathermaker crept northeast from Louisiana and brought rain to the mid-Atlantic on Tuesday the 18th. Some parts of the Appalachian Mountains received 3 to 5 inches of rain; eastern Virginia garnered less precipitation, but all in all it was a rainy day across the region. In the coming weeks I’ll ask my Earth’s Environmental Systems class to consider what happens throughout a drainage system when it rains, but this late September event was, dare I say, a textbook example of a flood wave passing through a basin and worthy of a post.
Watch the animated stream hydrograph of four U.S. Geological Survey gaging stations in the James River drainage basin to see the impact of this rainfall event. Before the arrival of the rain, the James and its tributaries were flowing steadily at relatively low late summer flow rates. The rain commenced late on Monday the 17th and continued throughout most of the day on Tuesday. The Bullpasture River, a small tributary stream in Highland County, responded with alacrity. At 9 a.m. on Tuesday the Bullpasture River had about 90 cubic feet of water passing down its channel every second (ft3/sec or cfs), by 3 p.m. the water level in the river jumped up by 5 feet, flow exceeded 4,000 cfs, and the stream was coursing above flood stage.
The rain came to an end on Tuesday evening. By that time flow on the Bullpasture was falling while the James River at Lick Run near Clifton Forge was about to start its climb, topping out at 6,400 cfs in the early morning on Wednesday. All the while, the James continued to flow placidly past the gaging stations in Scottsville and Richmond.
This pulse of water reached Scottsville on the morning of Thursday the 20th. Although the river never reached flood stage in Scottsville, the water rose ~3 feet in less than 3 hours and topped out with a flow of ~8,300 cfs just before midnight. It was mid day on the 20th when the James started a slow and sluggish rise in Richmond. The river continued to rise for over a day, eventually cresting at 11 p.m. on Friday the 21st. With a peak flow of 8,350 cfs in Richmond, the James did not reach its bank full discharge, but was well above the long term median flow.
The river distance between Clifton Forge and Richmond is ~350 km and it took the flood wave* nearly three days (65 hours actually) to traverse that distance. So what’s the average velocity of this pulse rolling down the river? After the river crested, all 4 hydrographs follow a similar trajectory with the flow dropping off exponentially over time. Why is the shape similar and what controls rate at which the hydrograph drops off?
Floods can wreak havoc on riverfront communities, especially if they arrive unannounced. But the surge from a storm through a drainage basin is relatively systematic and predictable. Upstream gage data make it possible to estimate both water height and the arrival time of high water, potentially averting dangerous situations. That’s one of the many reasons the U.S. Geological Survey gages rivers and it is a topic worth studying in the Earth’s Environmental Systems course.
*Although it did not actually flood along most of the James River, the concept is exactly the same.
August 29, 2012 by Chuck Bailey
William & Mary is back in business for another academic year. I teach my first class at 9 a.m. on Wednesday—Geology 110: The Earth’s Environmental Systems; it’s an introductory class with 200 students enrolled. Later, on Wednesday afternoon the College will gather for Convocation, and this is the ceremony that really kicks off the academic year.
In Earth’s Environmental Systems we’ll spend much time during the first week or two discussing the Sun and its relationship to the Earth. Consider the Sun and its path across the sky here on campus during the first day of the new semester, August 29th 2012.
The Sun will rise at about 6:36 a.m. (EDT) and will first appear above the horizon in the east-northeast. As morning progresses the Sun will rise ever higher in the sky, tracking out a southeasterly course. At local noon the Sun will be directly to the south and at its maximum solar elevation angle for the day (~62˚ on August 29th). Watch the animated graph to the see the path of the Sun across the Williamsburg sky.
Here’s a question: why, on August 29th, does local noon occur just after 1 p.m. rather than at 12 p.m.?
Insolation (incoming solar radiation) is the flow of solar energy intercepted by exposed surfaces. Insolation is a rate per unit area (watts/meter2). The amount of insolation received at any given point is a function of the solar elevation angle—the larger the solar elevation angle the greater the insolation. Insolation varies greatly as the solar elevation angle changes during the course of the day. Discerning how and why insolation varies across the Earth is fundamental to understanding the Earth’s environmental systems.
For many years Convocation has taken place in the courtyard of the Christopher Wren building, located on the west side of the Wren building. Convocation begins at 5:15 p.m. at that time the Sun will be 28˚ above the horizon at an azimuth of 260˚ (to the west-southwest), and as the ceremony rolls on the Sun will progress ever westward.
The Wren courtyard is well located to receive copious insolation during Convocation, and as such the temperature in the Wren courtyard is typically elevated to garish levels throughout the speeches and fanfare. Just ask the choir and faculty sitting in the courtyard, all tricked out in their robes and academic finery, about the temperature during Convocation. “It’s like being a disconsolate pig, all trussed up and stuffed into a three-sided brick oven…” groaned one of my colleagues. A three-side oven is an apt comparison as the vertical brick walls of the Wren building receive up to twice as much insolation as the nearby Earth’s surface, this heats up the bricks which, in turn, heat the surrounding air much more effectively than any blustery speaker ever could.
For this year’s Convocation, the College is moving the ceremony from the western courtyard to the eastern facade and front yard of the Wren building- what a brilliant idea! The venerable Wren building will provide shade for Convocation goers. After Convocation the incoming class of W&M students will proceed westward through the Wren building and emerge onto campus as the newest members of our community. This change in Convocation symmetry is a good idea. Paying due diligence to the physical reality of late August insolation and seeking a shady refuge in the Wren building’s eastern yard is a brilliant idea.
May 15, 2012 by Chuck Bailey
It’s just a day after commencement and I have landed in Arizona to await the arrival of 26 students enrolled in Geology 310: Regional Field Geology. The semester may be over, but the fun is not. Over the next three weeks we will traipse across the landscape of northern Arizona and Utah. We’ll study the geology of the Colorado Plateau from the bottom of the Grand Canyon to the top of the La Sal Mountains. This is the place where geologists go to see geology, well exposed and glorious. As access to the web permits, I’ll post status reports of our adventure.
May 3, 2012 by Chuck Bailey
The spring semester is rushing towards its conclusion. Classes have ended, final exams are underway, and graduation is just over a week away. The Geology Department’s class of 2012 is an accomplished and talented group. As I’ve noted before, all geology majors complete a year-long, independent senior thesis—this project is part of what makes the Geology experience at William & Mary unique. This year’s senior research projects were wide-ranging, from investigations of fossil shark tooth morphology, to lead geochemistry in New England soils, to magnetic anomalies in the Blue Ridge, to Mesozoic rift basin formation, and beyond! Two Saturday’s ago, the department came together for Senior Research Saturday, an eventful symposium in which seniors presented their research to friends, families, faculty, and peers. They played to a packed house and talks were followed by a suitably celebratory reception.
The class of 2012 not only talked up their science on campus, but also took to the road and presented the results of their research at professional meetings from Charlottesville to Asheville to San Francisco. Doug Rowland’s research on arsenic in groundwater at Jamestown was even highlighted by the History Channel. W&M geology students do meaningful research—but being able to effectively communicate that research is an essential part of being a public scientist. We put a strong emphasis on presentations in the Geology department and it’s rewarding to have our students showcase their research on a larger stage.
Earlier in the spring, our seniors led the departmental field trip and discussed their research at field sites from the Coastal Plain to the Blue Ridge Mountains. Watch a video from the trip and see for yourself! It is cool to see the geology seniors engaging their peers and teaching the faculty a thing or two! These activities don’t happen everywhere, but collaborative field trips and student leadership experiences are a delicious staple in the William & Mary Geology Department.