3/15/17. #22 - Subsidence - Rapid Sinkhole at Winter Park, FL in Rapid Subsidence Defined and Illustrated

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Audrey Maxwell
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Web Exercise #3 (Volcanoes) Late- closing at 1:00 today Web Exercise

question in Part II #22 - Subsidence - Rapid Sinkhole at Winter Park,

underground cavity removes support for rock above, which collapses

Subsidence Coal Mining OR by downward dissolution of soluble rock

Coal Mining - involves human-constructed cavity (underground coal

Coal Mining After underground roof supports are removed, subsidence

1 Web Exercise #3 (Volcanoes) Late- closing at 1:00 today Web Exercise #4 (Landslides) DUE WEDNESDAY Use Hazard City to answer matching question in Part II #22 - Subsidence - Rapid Sinkhole at Winter Park, FL in 1981 Rapid Subsidence Defined and Illustrated Creation of underground cavity removes support for rock above, which collapses over cavity (collapse sinkhole) Formation of collapse sinkhole Rapid Subsidence Coal Mining OR by downward dissolution of soluble rock (limestone) starting from surface (solution/subsidence sinkhole) A.Coal Mining - involves human-constructed cavity (underground coal mine); full recovery mining removes ~all coal. A.Coal Mining After underground roof supports are removed, subsidence occurs in days or weeks, indicated by circular or elongate depressions, ground fractures. Coal Mine Subsidence near Sheridan, WY 1

A.Coal Mining - room and pillar mining (~50% coal

Pillars = unmined areas that support overlying rock. A.

, lignite, bituminous in WY, ND) "soft coal" in weak

Great Britain, Wales Room and pillar mining (not coal)

Sinkholes - circular depressions (often water-filled)

other soluble bedrock (marble, gypsum, halite -

2 A.Coal Mining - room and pillar mining (~50% coal removal), subsidence may not occur (if rock is strong). Pillars = unmined areas that support overlying rock. A.Coal Mining Subsidence is worst for underground mines of low-grade coal (e.g., lignite, bituminous in WY, ND) "soft coal" in weak sedimentary rock; Examples = ND/WY, CO, PA, IL, western Great Britain, Wales Room and pillar mining (not coal) Rapid Subsidence B. Sinkholes - circular depressions (often water-filled) usually in limestone (dolomite, less often) bedrock and other soluble bedrock (marble, gypsum, halite - geologically uncommon). Rapid Subsidence- Sinkholes Sinkhole formed over natural cave Sinkhole formed over natural cave Rapid Subsidence - Sinkholes In US sinkholes are common in FL, AL, GA, TN, MO, PA incipient sinkhole 2

In US sinkholes are common especially in Florida In US

Sinkholes - Karst Topography Karst topography = landscape

disappearing streams Sinkholes - Where in Illinois?

= caves Monroe County, IL Formation of Sinkholes Form during

light/heavy groundwater removal) Step 1-Need source of acid

produced when CO 2 dissolves in water (atmospheric CO 2 in

Formation of Sinkholes Step 2 - During high water table

cave, greatly weakening rock (removes buoyant support of

3 In US sinkholes are common especially in Florida In US sinkholes are common especially in Florida Central Florida Sinkholes - Karst Topography Karst topography = landscape dominated by underground caves + surface sinkholes, lakes, disappearing streams Sinkholes - Where in Illinois? In southwest and northwest Illinois Green = sinkholes, black = caves Monroe County, IL Formation of Sinkholes Form during periods of fluctuating water table (rainy/dry seasons or light/heavy groundwater removal) Step 1-Need source of acid (carbonic acid, H 2 CO 3 ) to dissolve limestone H 2 CO 3 produced when CO 2 dissolves in water (atmospheric CO 2 in rain, decomposition of organic matter/humus in soil water) Formation of Sinkholes Step 2 - During high water table levels, slightly acidic groundwater (GW) dissolves limestone, creating underground cavities. Step 3 - During low water table levels, water drains out of cave, greatly weakening rock (removes buoyant support of water), collapse can occur quickly (hours to days). CO 2 (from soil and atmosphere) + H 2 O à H 2 CO 3 (carbonic acid) C org + O 2 à CO 2 (soil CO 2 ) 3

Sinkholes Artificial Sinkholes in Urban Areas Buried sewer lines, electric/cable wiring, underground subways

Example = very deep cavity (60 ft wide, 300 ft deep) formed in Guatemala City, Guatemala in May, 2010; due to

easily washed away More Guatemala photos at: http://www.csmonitor.

Create maps that show where the geology causes greater risk for subsidence B.

Regulate human activities that increase risk (e.g., groundwater pumping or coal mining) D.

4 Sinkholes Artificial Sinkholes in Urban Areas Buried sewer lines, electric/cable wiring, underground subways can disturb soil, causing voids to form. Example = very deep cavity (60 ft wide, 300 ft deep) formed in Guatemala City, Guatemala in May, 2010; due to burst sewer pipe or storm drain that produced underground cavity during heavy rain; loose volcanic pumice is easily washed away More Guatemala photos at: Galleries/In-Pictures/Guatemalasinkhole 28 images of sinkholes, man-made and natural, from The Atlantic: o/2013/07/sinkholes-when-theearth-opens-up/100552/ Clicker Question Based on what you have learned for earthquakes, landslides, volcanoes. What should society do to mitigate potential disasters due to subsidence? A. Create maps that show where the geology causes greater risk for subsidence B. Create laws or zoning rules that restrict land use in high-risk areas C. Regulate human activities that increase risk (e.g., groundwater pumping or coal mining) D. Educate public officials and the general public about processes and risks E. All of the above Mitigation of Rapid Subsidence Produce subsidence hazard maps and restrict land use, regulations for groundwater use or coal mining methods Sinkhole Hazard Map Coal Mine Subsidence Hazard Map Winter Park, central Florida in Sinkhole quickly grew over 48 hours, took several homes, 6 Porsches, parts of 2 streets, part of city swimming pool; ~100 m wide, ~30 m deep; damage = ~$2 million Winter Park Sinkhole 4

Winter Park, central Florida in 1981 Winter Park Sinkhole - Side View Winter Park, central Florida in 1981 - City

Sinkhole) Lake Chesterfield (Wildwood), Missouri in 2004 23-acre lake vanished in few days in this St.

western Florida in 2013 sinkhole opened suddenly beneath bedroom of house, man fell to his death into it; it

Drained Clicker Question Review: Which of the following best describes societal risk related to subsidence? A.

B. Subsidence can occur anywhere but because it is usually a fairly slow process, it causes little damage and

5 Winter Park, central Florida in 1981 Winter Park Sinkhole - Side View Winter Park, central Florida in City eventually stabilized and sealed sinkhole, converted it to beautiful urban lake Lake Rose (over Winter Park Sinkhole) Lake Chesterfield (Wildwood), Missouri in acre lake vanished in few days in this St. Louis suburb when it went down sinkhole due to collapse of limestone bedrock at bottom of artificial lake Seffner, western Florida in 2013 sinkhole opened suddenly beneath bedroom of house, man fell to his death into it; it quickly enlarged to ~30 m wide, ~20 m deep; house had to be demolished Seffner sinkhole Lake Chesterfield - Drained Clicker Question Review: Which of the following best describes societal risk related to subsidence? A. Subsidence is very unpredictable- we never know where or when it may strike and as a result it often kills people. B. Subsidence can occur anywhere but because it is usually a fairly slow process, it causes little damage and rarely kills people. C. Subsidence occurs only in certain areas that are well known. It causes substantial amounts of damage but rarely kills people. 5

SINKHOLES WHERE AND WHY THEY FORM

SINKHOLES WHERE AND WHY THEY FORM In the wake of the sinkhole that developed beneath a Florida man s bedroom, tragically killing the man as he was sucked into the earth, many people are searching for information.