Motorcyclist dies after being swallowed by sinkhole in South Korea

The cause of the sinkhole remains unknown. Seoul officials said they planned to conduct a “detailed and comprehensive investigation.”

“We will identify the cause of the accident as quickly as possible to ensure that such incidents are not repeated and that citizens can use the roads confidently,” Seoul Mayor Oh Se-hoon told reporters at the scene on Monday.

The sinkhole in the South Korean capital “appears to be due to collapse of infrastructure,” Andrew Farrant, a geologist at the British Geological Survey, told NBC News in an email Tuesday.

While natural sinkholes are caused by the dissolution of soluble rocks such as limestone and salt, other sinkholes are formed by the collapse of man-made underground voids, notably old mine workings and tunnels, Farrant said.

Since it’s hard to protect oneself from a hole suddenly opening up, more could be done to prevent the forming of sinkholes, with a good ground investigation being “essential,” he said.

Climate change, in particular more frequent and heavy rainfall, combined with increasing urbanization is likely to generate more sinkholes in future, he added.

Seoul officials said a total of 223 sinkholes appeared in the city from 2015 to 2024.

Sinkholes can be human-induced, with some correlated to land-use practices such as groundwater pumping and construction, according to the U.S. Geological Survey.

The incident in Seoul follows a similar one earlier this year in the Japanese city of Yashio, when a truck and its driver were swallowed by a sinkhole the size of a large swimming pool. The 74-year-old driver was never found after a two-week search.

Officials said the hole was most likely caused by a damaged sewage pipe.

There is no database for sinkholes in the U.S., but according to the U.S. Geological Survey the states with the most reported damage from sinkholes are Florida, Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania.

In December, a 64-year-old woman searching for her cat was found dead in Westmoreland County, Pennsylvania, several days after she fell into a sinkhole that authorities said was most likely caused by mine subsidence.