Sinkholes are natural depressions or holes created on the surface of the Earth by karst processes. Sinkholes do not possess any natural external surface drainage in the sense that when it rains, the entire water remains into the sinkholes which eventually drain into the subsurface. Sinkholes forms in different sizes as they can be less than a meter or over 100 meters in depth while multiple sinkholes have gone as far as one thousand feet wide and over eleven hundred feet deep (Sarisarinama, Venezuela). Similarly, sinkholes can adapt to different shapes; some with shallow saucer-like shape, while others would adopt a more vertical shape. Sinkholes are really very unpredictable making them be very dangerous. Their steady nature of formation means that without elaborate geological research, it would be difficult to identify any emerging changes, making collapses very dramatic particularly in the urban setup.
Sinkholes can occur naturally or through man-made. The natural sinkholes are caused by erosion of underground water. Their development begins long time before it actually appears. Incidentally, we might think that the ground beneath us has a solid structure, but rather it’s made up of dirt along with rocks and others sediments. Following continuous penetration of water in between rocks, sediments as it makes its way down to its reservoir, it happens that it gradually erodes the materials and rocks.
In other instances, the water flow increases to the level where it sweeps away the underground structure of earth. The underground structure gets to a point when it’s too feeble to withstand the surface of the earth; it collapses and forms a sinkhole. How is human responsible information of a sinkhole? There are particular activities that involve drilling, inappropriate compressed soil excavation, broken water pipes, mining and construction can lead to the development of small to an enormous sinkholes.
Apparently, water emanating from the broken pipe would seep through earth strata eroding the underneath ground resulting to formation of sinkholes. In certain instances sinkholes are formed when the land surface transforms. There are areas that are vulnerable to erosion, areas whose bedrock are made up of carbonate rock and limestone may lead to the formation of sinkholes. As water goes through degenerating plant debris, there is the tendency of it becoming acidic. Further over the period of time, the overlying sediments dissipate and a sinkhole forms. Sinkholes are of three types namely: (i) solution sinkholes- mostly common in areas whose surface has a thin soil cover, revealing the bedrock beneath to frequent erosion by water.
When water gradually seeps through the bedrock, it carries along with it small parts of rocks. This kind of sinkhole has a bowl-like shape which is quite huge (ii) Cover-collapse sinkhole – forms when the bedrock is spread out by a broad layer of soil. Then moment the bedrock is eroded, dents begin forming in the rocky areas surrounding it. The aftermath means a number of weak points would start to develop in the layers of soil.
In the end, it culminates to a level where the weak points result to large hole or sinkholes and (iii) Cover subsidence sinkhole- where the bedrock seems to be surrounded by soil and materials which are not compacted together. The moment the bedrock begins to erode, the clay begins penetrating through the dents filtering into the cracks left behind. Further, over the time, this great phenomenon is formed. Sinkholes can greatly change the topography of a particular area as it might as well change the course of a stream of the underground water.