Where sinkholes come from and why they happen

On August 23, a visiting Indian national was tragically killed after she fell into a sinkhole that appeared unexpectedly along Jalan Masjid India in Kuala Lumpur. The woman, Vijayaletchumy, 48, was walking on a concrete road outside Malayan Mansion when an eight-meter-deep sinkhole suddenly emerged and buried her alive. Relentless search and rescue attempts have followed, but the victim has yet to be discovered. Meanwhile, a wastewater specialist has raised concern that the victim may not have survived the rapid speeds at which water runs through sewer lines.

The incident has sent shockwaves through the local community and raised questions about the safety of urban infrastructure. Eyewitnesses reported hearing a loud cracking sound moments before the ground gave way, leaving bystanders in a state of shock and disbelief. Local authorities have cordoned off the area and are working tirelessly to assess the extent of the damage and potential risks to surrounding buildings.

Sinkholes form when a subterranean area cannot support the weight of its surface terrain. Simply explained, these cave-ins are produced by erosion beneath the ground surface.

This phenomena typically occurs in locations where the surface rock is composed of limestone or other forms of carbonate rock, salt beds, or other minerals that can be naturally dissolved by groundwater.

As flowing water gradually eats away at underground foundations and destabilizes the bedrock, concealed new caves appear. These may collapse, forming sinkholes. Underground erosion can occur either naturally or as a result of human activities.

Water movement is a natural force that exists all around us. It not only produces visible landscapes like karst pinnacles and sea stacks, but it also forms secret subsurface rivers and caverns. Limestone terrains are more susceptible to water erosion. Rain takes carbon dioxide from the soil before mixing with the subsurface water, making it slightly acidic.

This waterflow erodes the limestone sub-terrain, forming a network of caverns and voids. Cave-ins are especially common in the US state of Florida, which has a limestone-dominated landscape.

Urban planners and geologists are now calling for more comprehensive geological surveys in densely populated areas. Dr. Sarah Chen, a leading geotechnical engineer, emphasized the importance of regular underground assessments: "In rapidly developing cities, we often overlook what's happening beneath our feet. This tragic incident serves as a stark reminder that we need to invest in advanced technologies to detect and prevent such catastrophes before they occur."

Rapid urbanisation is also responsible for a high number of sinkhole accidents. Drought and high groundwater withdrawals, for example, can lower an area's buoyancy and cause subterranean portions to sink into cavities. Similarly, changes in groundwater composition caused by the entrance or removal of waterflows can flush away looser materials and result in sinkholes.

Faulty subsurface water lines may potentially cause disastrous urban sinkholes. Even a little breach between these pipes can introduce a huge volume of water into neighboring soil, dislodging it and eventually making the subsurface unstable. Despite the development of voids beneath the ground, no evident symptoms of instability emerge above it.

Because many of our utility pipes are located directly below ground, the paving of roads and paths frequently serves as a bridge over sinkholes, concealing sinister gaps below. If a cavity is not detected and repaired in time, the surface will eventually give way and consume everything above ground. Although sinkholes are rarely visible underground, various subtle clues may indicate a subterranean collapse.

Fractures in a foundation, the difficulty to properly close doors and windows, and the presence of circular ground fractures are all symptoms of ground instability that may indicate the emergence of a sinkhole.

Since Friday's sad accident, the government has advised Kuala Lumpur City Hall (DBKL) and all utility companies to do a mapping of all underground utilities in order to determine the state of the topography below and prevent further adverse incidents.

The incident has also sparked a global conversation about urban resilience and disaster preparedness. Cities around the world are now reviewing their infrastructure management strategies, with a particular focus on underground systems. Experts are advocating for the integration of advanced sensing technologies and real-time monitoring systems to detect early signs of ground instability. This tragic event in Kuala Lumpur may serve as a catalyst for improved urban planning and safety measures worldwide.

One of the most well-known sinkhole incidents occurred in Guatemala 14 years ago. On May 30, 2010, a massive sinkhole formed without warning in Guatemala City, the Central American country's capital.

The massive crater, which measured 20m wide and 90m deep, engulfed a three-story factory and its security guard. According to reports, the sinkhole formed as a result of a mix of events. Natural reasons, such as a tropical hurricane and a volcanic eruption, had damaged subterranean stability in the area, as has human activities, resulting from sewer pipe leakages. Sinkholes in natural settings have sometimes produced breathtaking natural views.

For example, the Great Blue Hole off the coast of Belize has become a renowned scuba diving spot. The marine sinkhole, measuring 300m wide and 135m deep, was previously a limestone cave system before the ocean rose.

As the search for Vijayaletchumy continues, the incident has highlighted the vulnerability of urban landscapes to natural phenomena. It serves as a somber reminder of the delicate balance between human development and the forces of nature. City officials and urban planners worldwide are now faced with the challenge of not only addressing immediate safety concerns but also developing long-term strategies to create more resilient and adaptable urban environments in the face of unpredictable geological events.