Geology Expert Shares the Factors Behind Sinkholes & Reveals the Signs That the Ground is Collapsing

Universiti Kebangsaan Malaysia (UKM) Engineering Geology and Soil Mechanics expert, Nor Shahidah Mohd Nazer, believes that the continuous rain for the past few days is believed to be one of the main factors in the occurrence of such sinkhole incidents.

An empty cavity

According to Nor Shahidah, this situation will cause the existence of empty cavities because the surface of the soil layer at the bottom is continuously eroded or lifted by sediment. This causes the surface to be just waiting for the time to collapse when the layer above can no longer support the load.

She explained that for that incident, we can see based on the video available on social media that there is a rather strong flow of water in the lower area.

"This water flow is one of the causes of the existence of a channel from the main river and it was worsened by the heavy rain that happened a few days before. Even before that incident, Kuala Lumpur was hit by floods and overflowing rivers caused flooding in several areas," she added.

She further said, "This indicates that the soil is in very high concentration and the water flow is exacerbating the erosion below. Therefore, some areas will experience continuous lifting of sediments causing the existence of relatively large empty cavities that will eventually collapse when the upper surface cannot support the available load."

"Also, sinkholes can occur as a result of the geology of the area that is based on limestone because the nature of limestone can dissolve in water so it can form a cavity that can cause the wall to collapse called a sinkhole. However, the dissolution of the rock takes hundreds or millions of years," she said when contacted by Gempak.

Signs of areas prone to the risk of sinkholes

Meanwhile, Nor Shahidah also shared the signs of an area being potentially exposed to the risk of landslides. "We need to pay attention to the surface, which will have a circular crack."

"It will appear when a cavity has existed on the base surface and the load on the surface is only temporarily accommodated by the pavement, so when the bottom is empty it will settle a little and form a circle," she stated.

"It also happens when there is a river in the area and the river suddenly disappears and appears in another place, this is one of the common examples of areas underlain by limestone. However at Masjid India, we could not observe this because the water flow of the river is at the bottom, " she explained.

To prevent the same incident from happening, Nor Syahida thinks that the incident can be avoided if the responsible parties conduct 'scanning' in areas where sinkholes have the potential to occur.

"Avoiding the occurrence of sinkholes is quite difficult because it is something that we cannot see with the naked eye unless we can see the round cracks, which are the infiltration of the surface that occurs."

"However, it is difficult to know the duration for such incidences to occur. Therefore, among the steps that need to be taken to prevent the same incident from happening again is that the responsible parties need to scan the areas where there is a potential for sinkholes to occur. They then have to close these holes using routing techniques. That alone is enough to cover the cavity," she said.