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

Concept Caching: Hydrothermal features in Iceland

From our Concept Caching image cache that hopes to promote student spatial awareness by relating specific features on the Earth’s surface with their visual character and GPS coordinates. Through the site photographs and GPS coordinates demonstrate core concepts in geography.  Images are “cached” for viewing by core concept and by region.  Images are certainly useful for introducing visual content to students in all Geography classes.

The Icelandic landscape is one of the most unique and interesting on Earth.  One of the few land-based rift zones, it is a standard discussion in any Physical Geography or Geology course.  Geothermal features are not only observed and studied, but they are harnessed for energy.  These geothermal features have also proved a “harsh reminder” for the power of the Earth, as discussed in the post, Geography Directions: Eyjafjallajökull: Geography’s Harsh Reminder. The March 2010 eruption of the Eyjafjallajökull volcano had upset the operation of transportation and economic networks that bridged the Atlantic.  The costs, in time and money, were staggering.  Even more unnerving is the nature of such a geologic event, as it was virtually impossible to predict and to mitigate.

Geography Directions: Eyjafjallajökull: Geography’s Harsh Reminder

From our Geography Directions site reviewing Wiley-Blackwell’s Geography Compass review journal covering the entire discipline.  Keep up with cutting edge academic geography.  These articles may be useful for introducing students to the discipline or may be appropriate for upper division Geography classes.

The eruption of Iceland’s Eyjafjallajökull on 20 March 2010 caught Europe dangerously off-guard. For two months, waves of ash closed some of the world’s busiest airspace. An estimated ten million passengers were left stranded, international train services collapsed under the heightened strain of people seeking alternate transportation, and governments were left to deal with angered airlines seeking to regain some portion of lost revenue. In total, over one hundred thousand flights were cancelled. The legal and political fallout of Eyjafjallajökull’s eruption continues today. A fundamental questions lies at the heart of this debate: why wasn’t Europe better warned or prepared? Amy R Donovan and Clive Oppenheimer (University of Cambridge) highlighted this problem in their March 2011 Geographical Journal commentary. The danger such natural events as Eyjafjallajökull pose, as Donovan and Oppenheimer argue, is that they lie outside the traditional realm of managerial governance.

Many natural events, however dangerous, lend governments two favours: first, relatively ample warning; second, comparatively localised impact. Hurricanes are an excellent case-in-point. Every summer NOAA, the United States’s oceanographic and atmospheric monitoring agency, continuously tracks existing storms and recalculates their future projectories. Excepting such hurricanes as Andrew and Katrina–most hurricanes cause damage across a limited geographic expanse before weakening significantly in strength. The snowstorms that rack the American northeast are similarly tracked in advance so that appropriate precautions can be taken (even if, in the event, those precautions prove inadequate).

The Eyjafjallajökull eruption, much like the 2004 Boxing Day tsunami and the 2010 Haiti earthquake, presents a very different scenario. Such events are difficult to forecast, even more difficult to contain, and–like other natural events–impossible to prevent. But, as The Geographical Journal commentary noted, preventative steps could have been taken. Although the Met Office’sVolcanic Ash Advisory Centre (VAAC), clearly noted the airspace risks posed by Iceland’s Eyjafjallajökull and Mýrdalsjökull volcanoes, this information was not included in the annual National Risk Register, nor did it predicate the implementation of ‘sophisticated, integrated UK or EU policy in advance of the recent volcanic activity’ (p. 2). One hopes that the Eyjafjallajökull airspace fiasco will serve as a reminder of our inability to tame the extremes of physical geography.

By Benjamin Sacks

To view the original article please visit the Geography Directions Blog.

Erosion, Mass Wasting, and Geologic Forms

Description: A collection of interactive images and panoramics that highlight geologic forms by photographer Martin van Hemert.  Click on the image to rotate the view, zoom in/out, and get a 360-degree look at erosion, mass wasting, and other concepts in Geology.

Source: http://www.utah3d.net/

Date last accessed: 29 April 2010

Links:
http://www.utah3d.net/SulpherCreek_swf.html
http://www.utah3d.net/DoubleArch1_swf.html

Discussion questions:
What kinds of mass-wasting processes occur where you live?  Can you identify any evidence that would suggest how rapidly or how slowly mass wasting is moving regolith downslope?  Look especially for signs of creep, which occurs almost everywhere.  Some clues are bent tree trunks, curved fences, lobes of soil on grassy slopes, and tilted gravestones.

Sedimentary Virtual Tour using Google Earth(tm)

Sedimentary Tour
Tour created by Professor Randy Rutberg, CUNY Hunter.

This virtual field trip is designed to show students examples of sedimentary rocks. The tour is designed so that students see each location from above. This helps them orient themselves geographically. I’ve created a number of locations (pushpins) and have labeled them with key words to help orient myself as I go through the tour. In some cases I have made the “pushpins” invisible so that they would not obscure the view.  These labels could easily be changed. I have included Mesa Verde, CO as I think this demonstrates the link between geology and anthropology. In this case, and in some others, the resolution is not sufficient to see the rock formations. However, the tour can be paused and then the blue squares can be “clicked.” This will bring up photographs of the rock formation.

Learning Objectives:

1.  Identify examples of sedimentary rock.

Download File: sedimentary_tour

On the Cutting Edge

Description: A website for Geoscience faculty On the Cutting Edge offers workshops, activities, online assets, and resources that are up-to-date on current research and teaching methods.  The project is supported by the National Science Foundation.

Date last accessed: 2/22/2010

Link: http://serc.carleton.edu/NAGTWorkshops/index.html

Earthquakes and Earth’s Interior

The Wiley GeoDiscoveries Media Libary has numerous animations, simulations and interactivities that help to explain the science behind Saturday’s earthquake in Chile.

Here are a sample of some of the media assets available [viewed best using Internet Explorer]:

Asset:  Earthquake Animation
Description: Simple Illustration of an earthquake at a strike-slip fault and the chain of events that may be brought about as a result, including bridge failure and flash floods.
Link:  http://www.edugen.com:30120/geodiscoveries/resources/ch09/print/earthquake_animation/index.htm

Asset: Earthquakes, Plates, and Margins Drag and Drop
Description: A drag and drop exercise in which you must correctly place the names of various plates on a diagram of the globe whose regions are highlighted according to quake depth.
Link:  http://www.edugen.com:30120/geodiscoveries/resources/ch09/print/plates_drag-drop/index.htm

Asset: Tsunami
Description: Simulation of a tsunami along a coastline.
Link:  http://www.edugen.com:30120/geodiscoveries/resources/ch09/print/tsunami/index.htm

Underwater Plate Cuts 400-Mile Gash

Description: Discussion of the plate boundaries related to the recent quake near Chili. 

Source: NYTimes

Date: 2/28/10

Link:  http://www.nytimes.com/2010/02/28/world/americas/28quake.html

Questions for Discussion:

What are some of the important questions about plate tectonics that remain unanswered today?

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