“In the Sacramento River delta north of San Francisco Bay, islands, agricultural lands and communities below sea level are protected from surrounding water channels by more than 1,100 miles of dirt levees, many of which date back to the California Gold Rush.” NASA now has a method to monitor them using radar. Quote from the NASA press release.
The Colorado Geological Survey has one of the best geology pages on the web. Their Geologic Hazards in Colorado page is so valuable because it has links to several excellent videos about the state’s important hazards.
“Radar data, if collected routinely from airborne systems or satellites, could at least in some cases foresee sinkholes before they happen, decreasing danger to people and property.” Quoted from the NASA press release.
Did you know that there are seven distinct depressions on Earth that are over 100 meters below sea level, and twenty-three that are over 10 meters below sea level and ten more that are at least two meters below sea level? We have a google map that points to ten of these depressions and a list of the remaining locations.
Most homeowners insurance policies have exclusions that make them worthless when the home is damaged by common geologic problems such as floods, earthquakes, landslides, mine subsidence, cavern collapse and expansive soils. When a home is damaged the homeowner often is surprised that his “all perils” policy has these exclusions.
In what has to be some of the worst luck, a sinkhole developed beneath the property of the National Corvette Museum, in the karst area of Kentucky, and eight of the most valuable corvettes on the planet fell in. Security video is posted on the museum’s website.
“The United States is losing wetlands in coastal watersheds at a significant rate, according to a new report released today by the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration. [...] It concludes that more than 80,000 acres of coastal wetlands are being lost on average each year, up from 60,000 acres lost per year during the previous study.” Quoted from the U.S. Fish and Wildlife Service press release.
“Scientists at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and Scripps Institution of Oceanography at UC San Diego have enhanced existing GPS technologies to develop new systems for California and elsewhere to warn of hazards from earthquakes, tsunamis and extreme weather events.” Quoted from the NASA press release.
“Communities and coastal habitats in the southern Chesapeake Bay region face increased flooding because, as seawater levels are rising in the bay, the land surface is also sinking. A USGS report concludes that intensive groundwater withdrawals are a major cause of the sinking land, or ‘land subsidence’, that contributes to flooding risks in the region.” Quoted from the USGS press release.
Scientists from the Arizona Department of Water Resources and the Arizona Geological Survey explain some of the land subsidence and earth fissure problems associated with ground water production in Arizona. The video, When the Ground Splits Open, is by Arizona Public Media.
An article on the New York Times website tells about the Bayou Corne Sinkhole, located in Louisiana above a salt dome where about 25 acres have subsided. The salt dome has been solution mined and the cavities produced by that mining have been used to store a variety of petroleum products.
The interactive Natural Hazard Viewer focuses on four hazards common to Arizona — geologic faults and earthquakes, earth fissures, floods and wildfire. Each hazard is described in detail and displayed as a layer on a map. Moreover, the natural hazard information is dynamic; site updates will occur as new or revised hazard data becomes available.
Editor’s Comment: Every state geological survey should have one of these!
A sinkhole about 200 feet wide and 90 feet deep has opened near the community of Sharon Springs, Kansas. Although no buildings have been damaged there is a problem with visitors venturing close the the edge and climbing in to explore the bottom.
National Geographic has an interesting article about how many small communities on the seaward edge of the Mississippi River delta are being lost to subsidence and sea level rise.
The community of Leeville (shown in Google map below) is featured in the article. If you toggle between “Map” and “Sat” you will see how the map greatly overstates the amount of dry land – at least on the day that the satellite image was acquired.
The Illinois Geological Survey has a publication titled: Karst Landscapes of Illinois. From the publication “Two conditions are necessary for karst landscapes (green areas on map): (1) Soluble rocks, generally limestone and dolostone, must lie at or near the surface of the ground. (2) The loose soil covering the soluble bedrock must be thinner than about 50 feet.”
The Florida Geological Survey has an informative poster titled “Florida’s Sinkholes”. It shows their geographic distribution, explains how they form, describes different sinkhole types, explains why they are a hazard and explains what to do if a sinkhole occurs near your home.
Did you know that most homeowners insurance policies do not cover damage from any type of subsidence? That includes collapse from sinkholes, oil production, ground water pumping and underground mining activity. Most insurance companies offering homeowners coverage exclude almost any type of geologic hazard from coverage – unless you make specific arrangements to acquire it yourself.
Last week a sinkhole opened beneath a home in Florida while the occupants were sleeping. One man’s bed fell into the sink and the efforts of family and rescue workers were not successful in retrieving him. Now he is presumed dead and demolition equipment is there to remove the structure while the sinkhole continues to enlarge. Injuries from sinkholes are rare but this situation shows how suddenly they can occur.
A large sinkhole under buildings in Guangzhou, China triggers their collapse.
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