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.

NEW Formation of Tornadoes and Mesocyclones Animation

Click here to view Formation of Tornadoes and Mesocyclones Animation.

NEW Coastal Processes Animation

Click here to view new Coastal Process Animation

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?

Climate Change in the Pacific: State of Emergency

As outlined in a previous post, “Climate Change in the Pacific:  Help we’re drowning,” Pacific islands are bearing the first clear environmental shifts of global climate change.  Not only are the islands being threatened by rising sea levels, their territory and societies ‘drowning’ in the process; but, climate change is combining with other environmental conditions to jeopardize the essential fresh water sources that these insular societies depend on.

On October 2011, the Pacific island nation of Tuvalu declared a national state of emergency.   The emergency is that the country’s fresh water sources are running out and others are unfit for consumption.  Some areas of the island were projected to completely run out of potable, fresh water within two days of the declaration.  The conditions that led to the state of emergency are related to the longer term climate changes, but also to seasonal shifts.  A seasonal, La Niña weather pattern has been causing drought in Tuvalu.  Below-average rainfall has been experienced since June or at least and is projected to continue into December.  Most of the country’s fresh water supply comes from collected rainwater.  Another source of freshwater lies under the ground.  Yet, this source is limited.  Tuvalu is a series of low-lying coral atolls.  The geology of coral atolls does not support deep groundwater sources.  Further, the shallow groundwater that is found on these islands is being compromised by rising sea levels as salt water infiltrates the groundwater supply.  A reporting of animals deaths leads Tuvaluan Red Cross officials to question the safety of the groundwater supply for consumption.  Considering the nature of groundwater recharge, and most acute in Tuvalu, the lack of rainfall is accelerating the infiltration of seawater into subterranean water features.  The impacts of water shortages are felt in the islands’ traditional subsistence agriculture activities as well as water rationing affecting basic water services.  Tuvalu’s neighbor and New Zealand territory, Tokelau followed up soon after with its own state of emergency declaration.

The relief is coming from international organizations like the Red Cross as well as from the government of New Zealand.  The people of Tuvalu and Tokelau are being aided with water collection supplies, desalinization units and plenty of bottled water.  The larger affects are still yet to come.  In particular, questions about the long-term settlement of many low-lying Pacific islands have implications for nationhood, cultural traditions, economic rights, and logistics of mass migration.

 

Yes, Virginia, it was an earthquake.

It was immediately apparent from the news coverage on Tuesday, August 23, 2011 that people on the East Coast of the United States are not at all accustomed to having the ground move beneath them. Reactions ranged from “I thought it was a terrorist attack” to “Scary!”, and the story displaced other national and even international news stories for days.

People generally did the wrong thing during the quake – many ran outside, even though FEMA recommends that people who are inside a building stay where they are , drop, take cover, and stay away from windows and other glass (http://www.fema.gov/hazard/earthquake/eq_during.shtm). Even the US Geological Survey office in Reston, Virginia was evacuated!

On the West Coast, where I happened to be during the quake (in Seattle), people in general (and news anchors in particular) took great pleasure in comparing the Virginia quake to others of similar magnitude that happen much more frequently in the seismically active Northwest. Lots of ribbing and mocking – mostly good natured – took place in the days that followed the quake.

East Coast earthquakes are much less common than West Coast earthquakes, because the eastern edge of the United States is what is called a passive continental margin. It is the edge of a continent (North America), but it is not the edge of a plate, and the edges of plates are where most seismic activity tends to occur. The edge of the plate on which the North American continent is riding is in the middle of the Atlantic Ocean, at the Mid-Atlantic Rift. That is where the North American Plate is moving apart from the Eurasian Plate (and, further to the south, the African Plate); earthquakes (and volcanic activity, as well) do indeed occur along that rift boundary.

Actually, East Coast earthquakes happen all the time; they’re just usually not this powerful. The August 23 quake was the strongest ever measured in Virginia. The causes of many of these intraplate earthquakes are not thoroughly understood. Some involve the activation of old, deep-seated faults. The area in which this particular quake occurred, the Central Virginia Seismic Zone, had experienced seismic activity before, but not along known, measured faults. The largest known historic earthquake in this area was a bit father to the west, in 1875, and was likely a bit less powerful than the 2011 quake. 

One geophysicist explained the cause of intraplate earthquakes like this: Imagine a plate the size of North America that is being jostled around on all sides by interactions with other plates. Obviously most of the earthquake activity will take place around the edges, but you’re also bound to be building up some stresses in the middle of the plate, too, which will eventually cause earthquakes to occur in the middle of the plate.

The details of the 2011 and historic quakes in the Central Virginia Seismic Zone can be found at the USGS Earthquake Hazards website (http://earthquake.usgs.gov/) . This is a truly rich resource that you should check out, if you haven’t already.

Of real concern is the lack of earthquake preparedness in the East. The general panic and uncertainty about what to do highlights this lack of preparedness. Another aspect is the general state of earthquake resistance of buildings in the East. Many older buildings are actually better suited to survive earthquake shaking than modern high-rises, which – unless specifically engineered to be earthquake-resistant, as they are typically now on the West Coast – are more likely to be rigid and subject to failure during seismic shaking. An interesting site with much information about cutting-edge research on earthquake engineering, damage assessment, and architecture is the Consortium of Universities for Research in Earthquake Engineering (http://www.curee.org/).

An additional educational resource that is worth checking out is Teachable Moments, provided by the University of Portland and IRIS Education and Outreach (IRIS is Incorporated Research Institutions for Seismology). You can find a Teachable Moment about the August 23 Virginia earthquake at http://www.iris.edu/hq/retm, and you can sign up to be on the Teachable Moments list-serv at the IRIS website (http://www.iris.edu/hq/programs/education_and_outreach/).

 Barbara Murck

Bluebird Hero

“His Blue Heaven” is an encouraging story about the recovery of a bird species previously in decline. Never listed as a Federal endangered species, the Eastern Bluebird (Sialia sialis) was nonetheless in serious decline through the middle of the twentieth century, and was listed as a rare or threatened species on some state lists.

Writing for the Boston Globe, Carly Gelsinger describes Robert Benson’s lifelong commitment to the songbirds. A retiree living south of Boston in the town of Stoughton, he has been enamored of bluebirds since he was a child, and was delighted when their recovery began in the 1970s. Since then, he has done whatever he can to improve their chances for survival. Finding areas with generally supportive habitat, his main focus has been to design, build, and maintain nesting boxes that provide safety for the birds.

The natural range of Eastern Bluebirds is the entire eastern portion of North America, yet another example of a pattern associated with the well-known 100th meridian phenomenon. It entered decline throughout that region for a variety of reasons, the most important of which was pesticides, particularly the chlorinated hydrocarbons that were the subject of Rachel Carson’s Silent Spring.  Hampering the recovery has been competition for habitat with such introduced species as sparrows and starlings.

Bluebirds are worth saving, not only for the beauty of their plumage and their song, but also because of their direct benefits to humans. For example, bluebirds can contribute to the production of environmentally sustainable wine grapes. As part of a program of integrated pest management, bluebirds can reduce or eliminate the need for insecticides. In recent visits to South Coast vineyards in Massachusetts, I have enjoyed observing these benefits directly!

In his journals, Henry David Thoreau demonstrated the value of prolonged, careful observation as the key to understanding the complex relationships within natural communities.  Similarly, Mr. Benson’s decades of careful observation allows him to understand bluebirds so profoundly that he has been able to design a variety of nesting boxes that are attractive to bluebirds but not to the sparrows or starlings that would occupy homes that would look very similar to most people.

Suggested activities:

1. Read the His Blue Heaven article carefully, and identify key geographic and ecological concepts beyond those mentioned above. Write an essay that describes how this story could compare to efforts to restore species or habitat local to your area.

2. Work with the North American Bluebird Society or similar organization to develop a project that would encourage species recovery on your campus or in your community.

Geo-STEM

Although education reform efforts in the United States have focused on basic writing and math literacy, many leaders are increasingly concerned about the erosion of the country’s leadership in the STEM disciplines:  Science, Technology, Engineering, and Mathematics. For this reason, STEM education is increasingly the focus of education reformers and stakeholders from regional business groups to state governments to the White House science advisors.

In my own outreach work with K-12 students (mainly at the middle school level), the relationship between geography education and STEM education is increasingly clear. Because geography is both a social science and a physical science, the relationships between geography and STEM are sometimes less than clear.

In a recent letter to Dr. John Holdren, one of President Obama’s top science advisors, a coalition of geography organizations makes a strong case for geography and geospatial education as part of a national STEM-education policy. The Coalition of Geospatial Organizations (COGO) includes both the Association of American Geographers and many organizations with more specific, technical missions, such as the American Society for Photogrammetry and Remote Sensing.

All of the groups agree that the current state of thinking on STEM is too narrow in its exclusion of geography. Specifically, they make the case for geographic education, which they note is missing from the PCAST report Prepare and Inspire: K-12 STEM Education for the Future. They make the following arguments for its inclusion:

• A 2009 White House budget calls for placed-based policies and programs
• A 2006 Department of Labor report identified geospatial technologies as one of twelve New and Emerging Occupations
• In 2010, the Department of Labor identified geography as a Knowledge and Skill Area central to employment involving the geospatial technologies it had previously identified
• The National Science Foundation provided $7 million in funding to geography research projects in 2009-2010
• National Geospatial Technology Center for Excellence is funded in part by NSF for the purpose of improving university-level geography education; strong geography education in the K-12 sector is a prerequisite for success in these efforts
• President Obama has said, “We must educate our children to compete in an age where knowledge is capital, and the marketplace is global.”
• The PCAST report itself warns that methods for teaching STEM disciplines must be developed that allows students to apply what they learn to real-world problems. Geography is an integrative discipline that is well-suited to this critical need.

The case for geographic education is not limited to careers and technology, of course; as I have argued before my own state government’s education officials, geography is an essential foundation for cultural literacy and public diplomacy as well, and are good preparation for a wide range of both STEM and non-STEM careers.

Suggested activities

1. Contact education leaders in your state – perhaps starting with the state’s Geographic Alliance – to learn the current status of geographic education in the state.
2. Review the 18 standards for geography education identified in the Geography for Life project. Which of these are most relevant to the geospatial careers for which the COGO group advocates?
3. Make a list of the geospatial technologies on which you rely – directly or indirectly – each day. How many e-commerce web sites, for example, employ Geographic Information Systems as part of their interface with potential customers?

Concept Caching: Glacier Bay

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.

Climate change, climate change, climate change.  It certainly bears repeating, if a refrain leads to awareness.  This seems like the dominant discourse to engendering climate change awareness.  Climate change will have (and is having) wide-reaching consequences, some we can predict and many others we cannot.  And of stories of affected landscapes, the high-elevation and high-latitude environments are the most often mentioned.  The post, Geography Directions: Permafrost, carbon and thermokarsts: the Arctic importance offers a slightly different spin on the hackneyed talk of glacial melt.  Instead of continuing to focus on the changes in quintessential landscapes-under-threat, like this one of Glacier Bay, Alaska, the article discusses carbon storage processes in periglacial landscapes.  By focusing on periglacial carbon storage, the article provides another avenue for understanding the Earth’s Carbon Cycle.  Further, periglacial landscapes are also undergoing transformation; however, these areas are also landscapes of human settlement and activity.  If periglacial, permafrost and thermokarsts aren’t sexy enough, then subsiding lands, sinking buildings, and trucks mired in mud should offer some tantalizing bases for climate change mitigation.

 

Geography Directions: Permafrost, carbon and thermokarsts: the Arctic importance

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 Arctic covers 5% of the total land mass of the earth and reaches across every longitude: it is important. It is estimated that 1.4 times more carbon is stored in permafrost than is currently circulating in the atmosphere, and there is 1.5 times more carbon in permafrost than is currently being stored in all the earth’s vegetation. William Bowden (2010) outlines this in a Geography Compass article, and explains the relationships between permafrost, thermokarsts and climate change.

Permafrost is soil or rock which remains below 0^oC for at least 2-3 years at a time. When permafrost thaws it loses its internal structure and subsides unevenly, and the resulting formation is called thermokarst. The transition from permafrost to thermokarst has important hydrological, geomorphological, biogeochemical and ecological importance to arctic landscapes. Globally, this transition may also release the stored carbon which, due to microbial processes, may be released as carbon dioxide or methane.

In April, a special edition on climate change was published by the journal, Philosophical Transactions of the Royal Society. It outlined key research questions required to better understand the impact of greenhouse gases on climate change. The arctic was prominently featured, and in particular the concern over permafrost melt and potential methane release. Scientists seem to agree that research is needed to understand the transitional process from permafrost to thermokarsts and the possible implications on the global climate.

By Caitlin Douglas

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

 

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