{"id":394808,"date":"2026-01-06T07:04:15","date_gmt":"2026-01-06T07:04:15","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/394808\/"},"modified":"2026-01-06T07:04:15","modified_gmt":"2026-01-06T07:04:15","slug":"heres-how-sinkholes-can-form-underground-long-before-anyone-realises","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/394808\/","title":{"rendered":"Here’s how sinkholes can form underground long before anyone realises"},"content":{"rendered":"

Residents in Melbourne’s north-east were shocked on Tuesday to discover a sinkhole had appeared<\/a> in their local park.<\/p>\n

A hole about 8 metres wide and 5 metres deep formed at the formerly-pristine AJ Burkitt Oval in the suburb of Heidelberg overnight.<\/p>\n

\"A<\/p>\n

The sinkhole appeared suddenly, with residents left shocked at the crater it left on their local oval. (ABC News)<\/p>\n

While sinkholes can appear suddenly, the holes that form them could be slowly forming over the course of years or even centuries.<\/p>\n

Due to a variety of reasons from erosion to nearby human activity, a cavity might form underneath the earth.<\/p>\n

\"Guatemala<\/p>\n

In extreme cases a sinkhole can consume entire buildings, like this Guatemalan sinkhole in 2010. (Reuters: Casa Presidencial)<\/p>\n

Over the top of the cavity, a surface layer of earth forms a ceiling, making the ground appear unchanged to anyone looking at it.\u00a0<\/p>\n

But eventually, when the surface layer becomes too thin and weak, it collapses and leaves a sinkhole.<\/p>\n

What causes sinkholes?<\/p>\n

There are a range of reasons a sinkhole might form, each with their own timeframes.<\/p>\n

On the longer end of the scale are sinkholes formed by a chemical process known as suffosion.<\/p>\n

In this case, groundwater dissolves certain kinds of carbonate rock like limestone, hollowing out the earth over thousands of years.<\/p>\n

It’s this long, gradual process that created the ancient limestone sinkholes seen around Mount Gambier<\/a> in South Australia.<\/p>\n

\"A<\/p>\n

The Umpherston Sinkhole in Mount Gambier is an example of an ancient sinkhole formed by gradual chemical processes. (ABC South East SA: Eugene Boisvert)<\/p>\n

But sinkholes can form much more quickly if the circumstances are right.\u00a0<\/p>\n

With enough water present, soil can go through a process called liquefaction, becoming so saturated that it becomes weak and prone to collapse.<\/p>\n

Flowing groundwater can even carry off soil away from the area altogether, creating cavities underground.<\/p>\n

\"Water<\/p>\n

A large 2020 sinkhole in Kew was caused by a broken pipe for storm water access. (Supplied: Lou Miller)<\/p>\n

A broken stormwater pipe was blamed for a sinkhole forming in a Kew park in 2020<\/a>, while a burst water main in Port Melbourne created a car-swallowing sinkhole<\/a> in 2014.<\/p>\n

\"Cars<\/p>\n

This sinkhole opened up after a water main burst in Port Melbourne in 2014. (ABC News: Roy Frattinger)<\/p>\n

In some cases, soil that is weakened by water is pushed over the edge by human activity.<\/p>\n

Investigators say nearby tunnel boring machines in Melbourne’s north-east likely contributed to the appearance of the sinkhole on Tuesday in Heidelberg<\/a>.<\/p>\n

In 2023, tunnelling through wet, sandy soil at the Snowy 2.0 site also caused a sinkhole to open up and bring digging to a standstill.<\/a><\/p>\n

Loading…<\/p>\n

Sinkholes formed by digging can lie hidden for decades, before finally opening up.<\/p>\n

In Ballarat, where the terrain is dotted with old mineshafts, sinkholes are a common occurrence, with one Ballarat East resident returning home in 2007\u00a0to find his backyard had\u00a0caved in<\/a>.<\/p>\n

\"ses<\/p>\n

In 2007 a sinkhole emerged beneath this\u00a0home in Ballarat East, reaching an estimated depth of 5 metres. (ABC Ballarat: Jarrod Watt)<\/p>\n

How easy is it to detect sinkholes?<\/p>\n

The ceiling that remains on a sinkhole, even as the ground beneath it is eroded away, makes them difficult to detect before they collapse.\u00a0<\/p>\n

Francois Guillard is a senior lecturer in geotechnical engineering at the University of Sydney, and said predicting where sinkholes would form was difficult.\u00a0<\/p>\n

\"A<\/p>\n

Sinkhole formation depends on the state of the soil underground, making it difficult to identify where one will appear. (ABC News)<\/p>\n

“The visibility of it at the surface is actually quite sudden, because it’s the collapse of the roof over a cavity that can have been formed for a year,” he said.<\/p>\n

“That makes things quite difficult, because you would need to know really what is the condition of the soil underground, and that’s something that is hard to assess in general.”<\/p>\n

There are a range of techniques in use to attempt to identify sinkholes, from taking soil samples to analysing satellite imagery.<\/p>\n

Seismic waves are also used to detect changes and weakness in the soil underground.<\/p>\n

\"An<\/p>\n

A large sinkhole beneath a major road in Tokyo swallowed a truck in January 2025. (Kyodo\/via Reuters)<\/p>\n

But Dr Guillard said it was difficult to perform this kind of modelling over a wide area.<\/p>\n

“It’s possible to do this kind of assessment on a localised region but on broader areas, it’s more difficult,” he said.<\/p>\n

“There is still quite active research in this area to try to improve this kind of tool.”<\/p>\n

How do you fix sinkholes?<\/p>\n

Generally, the way to fix a sinkhole is to fill it back in.<\/p>\n

Geotechnical experts will fill the hole, often with special resins or concrete to stabilise the soil.<\/p>\n

But Dr Guillard said identifying the original cause of the sinkhole was paramount in preventing further damage.\u00a0<\/p>\n

\"Sinkhole\"<\/p>\n

Repair works are set to get underway at the Heidelberg sinkhole soon. (ABC News: Danielle Bonica)<\/p>\n

“Controlling underground water flow can be quite difficult,” he said.<\/p>\n

“You need to control the drainage and you don’t want to just divert the water because then you can have the same problem 100 metres away.”<\/p>\n","protected":false},"excerpt":{"rendered":"Residents in Melbourne’s north-east were shocked on Tuesday to discover a sinkhole had appeared in their local park.…\n","protected":false},"author":2,"featured_media":394809,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[64,63,17710,10588,210885,210886,85],"class_list":["post-394808","post","type-post","status-publish","format-standard","has-post-thumbnail","category-sports","tag-au","tag-australia","tag-erosion","tag-geology","tag-sinkhole","tag-soil","tag-sports"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/394808","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=394808"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/394808\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/394809"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=394808"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=394808"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=394808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}