What causes sinkholes? This is the question that haunts every house owner in all areas of the world.
Sinkholes occur due to underground faults or a fracture in the earth’s surface. Underground pressure and weight may also cause a sinkhole to form. When there is a collapse in the earth’s surface, the force of the collapsing layers can push the soil outwards and create a hole. The hole then gets filled with air and the soil expands back again.
There are many different types of sinkholes but the most common type is a “cover-subsidence sinkhole”. It is a result of the soil shifting from beneath the foundation causing the floor to cave. The soil movement can be triggered by an unexpected rise in sea or lake levels, wind, rain, and even melting ice. In this type of sinkhole, the rim of the hole is higher than the level of the surrounding ground, which may make the rim unstable.
The second most common type of sinkholes occurs when there is an over-pressure on the soil close to the foundations. Over years of pressure, it can cause cracks in the strata. This cracking leads to caverns and cavities, which can hold groundwater. Eventually, these cavities expand and collapse, exposing the surrounding ground water. If it rains for a long time, the excess moisture can cause mudslides and flash floods.
Sometimes an area that receives little rainfall or hardly any rainfall can have sinkholes due to poor external drainage. Usually the land around the sinkhole gets saturated with mud and is difficult to drain away. This type of sinkhole can sometimes be confused with a subsidence hole. A subsidence hole occurs when the soil near a house slips down because of the natural movement of the earth.
Another type of sinkhole occurs when the ground nearby sinks with time. This often happens when there is a fault in the earth, causing the soil to slip off its axis. When this happens, the surrounding soil shifts with it and makes a path for water to flow into. This can result to cave-in, which is a kind of cover-collapse sinkholes form. Cover-collapse sinkholes form gradually as the ground around it starts to erode.
One of the known factors that can make sinkholes develop is by the presence of gypsum. Gypsum is a type of soluble salt, and it forms the base material for the formation of a sinkhole. Over years, the build-up of gypsum can take a big amount of time. As a result, the soil around the hole starts to erode, exposing the exposed cavity, which can either be filled with dirt, or soil similar to what was used previously.
Scientists have pointed out that the most probable cause of sinkholes happens to be the changing of the gravitational force on the earth’s surface. Although they have not been able to explain exactly how this occurs, they have noted that there are instances where they occur even when there is no present gravitational force. These cases, they noted, are more likely to occur near mountain ranges where there are less vegetation and a higher concentration of clay mineral deposits. Clay, they noted, is a very potent absorbent. If it were to soak up some of the groundwater, which is necessary for holding the groundwater in place, it would allow the sinkholes to form.
Aside from the above-mentioned factors, another factor believed to play a role in the occurrence of sinkholes is the lack of adequate drainage. Some areas, particularly those that do not have any man-made structures on them, are prone to sinkholes. Sinkholes are actually small cavities on the bedrock, and they usually occur when the soil is subjected to great amounts of pressure. Another possible factor that can lead to the occurrence of sinkholes is the dissolution of limestone. When limestone is exposed to great amounts of pressure, it may result in the cracking of the limestone, which leads to the formation of cracks in the ground.
When these cracks widen and become larger, they might eventually connect with each other, resulting in sinkholes.
Provided by Antonio Westley
Disclaimer: This article is meant to be seen as an overview of this subject and not a reflection of viewpoints or opinions as nothing is definitive. So, make sure to do your research and feel free to use this information at your own discretion.