Sinkholes: Illinois vs. Florida

Recent sinkhole events in both Illinois and Florida made national news and highlighted a little-known geohazard, raising many questions and concerns of property damage and safety. Sinkholes are a common surface expression found mostly in regions of karst topography. Karst is a Slavic word for a large, flat field, which is typical of the landforms in Slovenia that contributed the name. The presence of sinkholes tells the geologist that a particular type of geology, hydrology, and environmental impacts can be expected. Most sinkholes are formed by the dissolution of calcite-bearing rocks. As precipitation (H₂0) makes its way through the hydrologic cycle, it picks up carbon in the atmosphere, soils, and rocks in dissolved form (CO₂). This creates a mild corrosive known as Carbonic Acid (H₂CO₃), which can dissolve the mineral calcite found in limestone (CaCO₃) and dolomite {CaMg(CO₃)₂}. Other sinkholes are formed by the dissolution of evaporites or anhydrites of copper (CuSO₄), calcium (CaSO₄), and gypsum {CaSO₄ (2H₂O)}. Regardless of their formation, the hazard exists when this process leaves a cavity beneath a thin soil or rock covering. The cavity continues to grow until a critical mass is reached where the roof can no longer hold the weight and it collapses. Likewise, this can occur when weight is added by someone or something (cars, infrastructure, golfers, etc.).

There are several types of sinkholes but most occur as either solution sinks, where rock is slowly dissolved but there is no connection to the subsurface, or collapse sinks, which overly cave systems and transport material to the subsurface creating an excavation with a throat. The former are prevalent in karst but are relatively harmless, while the latter are more rare but far more costly and dangerous, since they can extend several hundred feet vertically and spread laterally for hundreds of feet. The sinkhole that caused the death of Jeff Bush in Hillsborough County was of the collapse variety, slowly forming over hundreds or thousands of years, culminating in a brief collapse event. This sink was 20-30 feet wide and 30 feet deep. Unfortunately for residents, this is a common part of the landscape there, as much of Florida has karst topography. The limestones in Florida are porous and the water table is high, creating much dissolution that forms thousands of sinkholes and caves. Many of these will have a thin rock or soil mantle, which enhances the hazard, as we are often unaware of their presence until collapse initiates.

The Illinois event represents another type of sinkhole, known as suffosion or soil-piping. This occurs when water transports soil and overburden to the subsurface creating a cavity. While these occur naturally, they are aggravated by human influences in the watershed that change hydrology and drainage, such as pavement, rooftops, and other impervious surfaces. These runoff modifications can cause excessive soil and substrate to be transported to the subsurface, creating a sinkhole. Likewise, this process occurs when there are leaks or breaks in water pipes. Fortunately, Mark Mihal suffered only a dislocated shoulder when a suffosion sink opened up under his feet on the golf course. The most likely culprit is a leaking irrigation pipe commonly used to water the green.

So what can we do to prepare and mitigate damages and loss of life from sinkholes without expensive and technical seismic and geophysical equipment? Primarily you should be aware of where you live and the range of local geologic hazards. Those living in earthquake country have management and emergency preparedness plans. Living in karst similarly requires knowledge of human impacts and geohazards found there. Hazard mapping of these features in karst can offer awareness and contribute to local management and best practice plans to help mitigate property damage and loss of life. Potential hazard zones can be established to restrict or regulate development in high-risk areas. Only active awareness and participation within an integrated management plan in karst topography will help avoid future loss of life and property damage.

‘The testimony of rocks’ in science v. creationism

The ongoing battle between creationists and scientists is still raging. Polls conducted over the last 30 years have indicated that more than 40% of Americans believe that God created life fewer than 100 centuries ago (Gallup, 2012). A majority of this population also believes that scientists have been actively perpetuating an anti-faith conspiracy for centuries.

In the Geological Society of America‘s November issue of GSA Today, David Montgomery’s account of this debate condemns creationists for abandoning “faith in reason” and discarding a centuries-old theologic understanding that “rocks don’t lie.”

Click to read more of Montgomery’s account The evolution of creationism from GSA Today. Additional commentary is available here: Geology and creationism.

More jobs, fewer funds for the Geosciences

The geosciences are hiring. Thanks to booming mineral and petroleum industries and increasing awareness of climate change, geoscience jobs are multiplying faster than the number of qualified applicants in the United States, Europe, and Asia.

Despite this increased demand, universities across the globe are downsizing their geosciences programs. Last year, Open University, which boasts about 4,500 Earth Science students per year, cut all residential geoscience courses. The university’s reasoning? Read Steven Drury’s article for earth-pages  to find out.

The production of geoscientists: a cautionary tale from the Open University

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Living Lectures

By Wiley author Barbara Murck

“We don’t need to go to lectures, we’re livin’ it.” – Cali, one of our fantastic students in the University of Toronto’s Ecuador 2012 Summer Abroad course.

I’m passing along this quote, just in case you needed additional reinforcement on the value of field experiences for students. Cali said this spontaneously while we were hiking up the volcano Bartolome in the Galápagos Islands, and it quickly became – for me – the quote of the course.

Certainly very few students (and very few profs) get the opportunity to visit the Galápagos, the Andes, or the Amazon, and we went to all three of them for this course. The trip was amazing – life-changing – for all of us, in many ways. Swimming with sharks, sea lions, and penguins, seeing a pygmy marmoset from less than 2 meters away, and hiking up the highest mountain on the Equator (Volcan Chimborazo) were some of my personal highlights.

The trip was more than just fun and eye-opening. It was also physically and mentally intense, and it had a very serious academic core. The ground we covered, both literally and academically, was impressive. We went from freezing in parkas and hats at 5300 m altitude in the Andes, to hot and sweaty in rubber boots in the Amazon, to snorkeling in the Pacific Ocean in San Cristóbal. Academically the breadth was just as significant. Between my own lectures and those of my Canadian and Ecuadorean co-instructors we covered everything from fisheries, tourism, and oil development to island biogeography, rainforest ecology, and invasive species to hotspot volcanism, subduction zones, and El Niño – and more.

For me there were some “small” moments that really drove home the importance and impact of teaching in the field. In the Galápagos I gave a lecture on atmospheric and oceanic circulation systems that most of my students had heard already in their first Environmental Science course, and probably in other courses as well. But teaching about the trade winds in a classroom in Toronto is one thing; asking students to monitor the wind every morning and check the clouds brings them to a whole different level of understanding. When they realized that, yes, in the Galápagos the wind actually does blow steadily from the SSE every day, all day long, the significance of the trade winds and how the whole atmosphere circulation system fits together really solidified their understanding. Walking upright in a lava tunnel on Isabela Island and measuring thick sequences of pyroclastics in the Andes demonstrate the power of geologic processes in a very immediate and physical way. Seeing penguins that are endemic to the tropics, and understanding the role of the cold Humboldt and Cromwell currents in moderating temperatures on land makes a connection between life and the physical environment in a way that is virtually impossible in the classroom.

Although it was truly great to have the opportunity to go on this trip to Ecuador with our 32 wonderful students, I do actually believe quite strongly in the value of field experiences closer to home. We have instituted a program of field trips for our introductory Geography students. There are 300 students in the course, and the instructor takes 100 to 150 of them at a time (with help from Teachings Assistants) on a series of field trips in the Toronto area. They visit housing projects, look at shorelines, take soil samples, monitor the weather, and look at urban development. For some of them it seems like it must be the first time they have set foot outside of their own homes, the world is so new to them. This is not the case, of course, but it definitely is new for them to be looking at their world through academic eyes.

We can offer this type of experience to our students. We can’t get all of them to the Andes, the Amazon, or the Galápagos, but we can make an effort to ensure that every student gets outside – preferably a little bit out of their comfort zone. Ultimately, if we want our lectures to be meaningful we need to get students away from the lecture hall and into an environment where it all comes together and makes sense.

Latitude by the Glass

In his recent article Chardonnay with Latitude, Boston Globe wine and food writer Stephen Meuse draws attention to the geography of wine. As with anything that varies spatially (such as coffee), geography can be used to learn about wine, just as wine can be used to learn about geography. The clever title of Meuse’s article reflects his decision to write about several wines whose common characteristic is particularly geographic: they are all made from grapes of the Chardonnay variety, but from the northernmost extremity of that grape’s geographic range.

Meuse describes the influence of both soil mineralogy and climate on grapes, and then provides tasting notes and retail information for a number of wines from close to 50 degrees North latitude. All of these wines are found in Europe, five degrees or more north of the northernmost wines in the Americas, though Meuse does not explain this difference, which has to do with the directions of currents in the north Atlantic Ocean. Northwestern Europe is warmed by the Gulf Stream, just as northeastern North America is cooled by the Labrador Current.

In his book The Geography of Wine, geographer Brian Sommers explains not only the geographic factors underlying terroir; he also examines the economic and social geographies of wine consumption and distribution. Wine, in fact, is of such interest to geographers that an entire specialty group of the Association of American Geographers is dedicated to wine scholarship.

Suggested activity:

Working as individuals or small groups in a class, identify common food or beverage items. What ingredients are required to produce each item? What factors determine where those ingredients can be produced? To what extent has human geography — such as patterns of trade or migration — influenced the location of these ingredients? What patterns of transportation are involved in producing the ingredients, processing the food or beverage, and delivering the product to consumers?

Tortilla Curtain

Former British Prime Minister (and future Nobel Laureate) Winston Churchill introduced the use of “curtain” as a metaphor for barriers in global geopolitics. He first used the term Iron Curtain in a 1946 speech at Westminster College in Fulton, Missouri. He applied coined the phrase to describe the rapidly growing post-war rift between the West and those countries allied with or controlled by the Soviet Union. That divide quickly became so profound that many students are likely to be unaware that the United States and the USSR were allies in World War II.

Churchill’s great, metaphorical divide is most often associated with the very tangible Berlin Wall (1961-1989), whose physical dismantlement is correlated with the demise of the Soviet Union and the fading of the Iron Curtain concept. The term

Bamboo Curtain was the eastern counterpart to the Iron Curtain, applied to the boundaries between Asian command economies (such as China and North Korea) and neighboring capitalist countries. The term was never as widely recognized as Iron Curtain, both because of its discontinuity and because alliances among communist countries were frequently shifting.

In his 1995 novel Tortilla Curtain, T. Coraghessen Boyle applies the curtain metaphor to cultural divides within North America.