Geology And Geophysics

How Sinkholes Form



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When witnessing their destructive potential, knowing how sinkholes form can become a more intriguing piece of knowledge. Sinkholes explained in the simplest way are holes, or depressions, in the ground. A sinkhole can also be said to be a hole in the surface of a land mass. Sinkholes differ in size; in fact, one of the sinkholes that became famous due to its size is located in Florida, near Tallahassee. It measured about six square miles, and was responsible for the disappearance of Lake Jackson in the year 1999. Sinkholes can happen any time without warning, and some of them can easily swallow cars, houses or even drain a lake. It is good to know the reality of the danger of sinkholes and the locations where they can occur, but knowing how sinkholes form is important as well.

Sinkholes are unique in that their activity is not always manifested in the surface of the land; therefore,  it is difficult to detect them beforehand. In other words, there is usually subterranean activity happening before a sinkhole forms, but then it is not noticed until it shows up as a huge hole. There are a few different ways that sinkholes form.

Dissolution of Limestone

Limestone, although considered a rock, is porous in nature. Due to that factor, limestone is capable of breaking, cracking and also dissolving. The development of sinkholes can be traced from many factors; however, the most significant of them all is mineral dissolution. For illustration purposes, here is a simple explanation on how it could occur: As the water moves through the earth or the soil, it becomes increasingly acidic due to the chemicals, both natural and artificial, that it picks up along the way. The natural acid retention happens because the water reacts with decaying and living plant matters. Moving along, the water reaches the limestone underneath. As a result, it will gradually dissolve the limestone; therefore, creating cavities and voids beneath. The soil on top of the limestone begins to collapse, and this collapsing creates sinkholes.

Development of Land

Usually, the process of development regarding sinkholes is gradual, but there are times when its activity becomes rapid, in terms of how sinkholes form. One of the situations that increases the development of sinkholes can be attributed to a construction improvement, or land development. When this occurs, the earth’s surface produces changes, concerning its distribution of weight and load on the soil underground. Some of the things that can most likely trigger a sinkhole activity are changes of water level in the ground, new buildings and houses, roadways, and the creation of retention ponds.

Diversion of Water Flow

Sinkholes are dangerous, since they can happen without warning. Sometimes, there is water running below the surface. As long as the water is running between the roof and the bed of the soil underneath, it is safe. The water supports the weight of the soil. However, if the said water is gone, then the land above it crumbles. Nature does the diversion of water on its own in most cases, but people in some instances do contribute, too; for example, in mining activities which are rampant in many countries, drinking water projects and irrigation activities that benefit thousands of farmers.

Knowing how sinkholes form could hopefully prevent future instances occurring that would threaten to cause harm to human beings; however, the unfortunate state of world industry dictates that the same behaviors that threaten soil stability will only continue in operation for quite some time.

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