Subsidence is a depression of the ground on the surface due to extraction of minerals from underground coal mines. It occurs in two forms, namely, trough and sinkhole subsidence. Trough subsidence is a depression covering a large surface area whereas sinkhole subsidence is a localized phenomenon occurring due to sudden collapse of overburden into the underground voids.The impact of sinkhole subsidence on the environment can occasionally be very catastrophic,destroying property and even leading to the loss oflife. The environmental components can be defined aspublic health and safety, social relationships, air and waterquality, flora and fauna.The paper discusses the causes and Impact of sinkhole subsidence on various environmental aspects. The paper also highlights the researchers who work on different models for risk assessment of sinkhole subsidence, this has been done by using various methods, namely, empirical, semi-empirical, remote sensing & GIS, numerical method and geophysical method to save human life, environment and prevent the loss to property.
What causes sinkholes? It's a question that's been on many minds lately, following the news that a sinkhole had opened suddenly beneath a home not far from Tampa, Fla. last Thursday and swallowed up a man who lived there.
As the name suggests, sinkholes are naturally occurring holes in the surface of the earth. Sinkholes can form gradually or -- as in the tragic case in Florida -- suddenly. They form in areas where water flowing underground has dissolved rock -- typically limestone -- below the surface, leading to the formation of underground voids into which the surface sediment falls, according to the website of the Florida Sinkhole Research Institute. They vary in size from 1 to 600 meters.
Sinkholes are found all over the world. In the U.S., sinkholes are especially common in Texas, Alabama, Missouri, Kentucky, Tennessee, Pennsylvania, and Florida, according to the U.S. Geological Survey.
Experts say that thousands of sinkholes form in Florida each year, the Associated Press reported. In addition to sitting on highly porous limestone, the state has additional factors that can lead to the formation of sinkholes, including extreme weather and aquifer pumping.
"There's hardly a place in Florida that's immune to sinkholes," Sandy Nettles, the owner of a geology consulting company in the Tampa area, told the Associated Press.
In an effort to prevent injuries, deaths, and property losses caused by sinkholes, scientists have tested various methods of detecting the underground cavities that can lead to sinkholes. These include radar, seismography, and electrical resistivity testing, according to the institute's website.
You don't have to be a scientist to be able to recognize certain signs that a sinkhole is about to open up. A brochure issued by the Southwest Florida Water Management District lists several sinkhole warning signs, including slumping trees or fence posts; the formation of small ponds in areas where water has not collected before; wilting of small, circular areas of vegetation; and structural cracks in walls.
But despite efforts to spot sinkholes before they occur, there are still plenty of unpleasant -- and occasionally tragic -- surprises. Said Settles, "There's no way of ever predicting where a sinkhole is going to occur."