What Are Sinkholes, How Do They Form And Why Are We Seeing So Many?
Despite the insurance company taking responsibility, the recent sink hole case in Charlton, London, has us a little uneasy. So, we thought we’d take a look into just what causes them and what we can do about them (if anything).
More recently, the UK has seemed to be experiencing a large case of sinkholes. It’s not just the London case that prompted this piece, either. Over the past few months, we’ve experienced a number of sink holes opening up, and it’s not just on the road – a 15ft sinkhole opened up on a residential road in Hemel Hempstead, resulting in the evacuation of residents.
It’s not just the UK suffering from sinkholes. A case not long ago involved a 40ft wide sinkhole opening up in the US, swallowing a number of rare cars displayed at the national Corvette Museum in Georgia.
Despite none of these cases actually causing any physical injuries to a human being, that’s not to say that these sinkholes are safe. Sinkhole effects are surprisingly easy to deal with, despite obviously looking very dangerous, and that they are but once they have exposed themselves, councils are able to deal with the matter safely.
One of the more serious cases of sinkholes, that we know of, was back in 2010 in Guatemala City, when a crevice 65ft wide and a massive 100ft deep opened up. This incident took the lives of 15 people, while consuming a three-story building. This particular sinkhole was caused by a number factors; water from storm Agatha, as well as water damage from a local sewer pipe.
So, what exactly is a sinkhole?
Well, a sinkhole is a hole that forms underground which has basically eroded, which is often caused by a number of factors. The Earth is formed of a number of plates that are constantly moving and underlying ground, over time, loses its structure, under the laying of the tarmac of roads. As the hole gets bigger the cover, or tarmac, can’t support its own weight and collapses, exposing the sinkhole.
More often than not, these crevices are caused by natural processes, however, an influx of water, say from a burst water pipe, can also weaken the structure. You never know how big they are until they expose themselves and they can vary in size, massively. Sinkholes usually happen on karst terrain, which is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum – any substance which is able to be dissolved by water.
There are predominately two types of sinkhole; a cover-subsidence sinkhole, which forms slowly over time and a cover-collapse sinkhole, which can appear suddenly and at pretty much any time – both of which are formed by the processes described above.
But, why now? Why does it feel like there are a lot of sinkholes forming lately? Well, the majority of recent sinkhole occurrences have taken shape due to the effects of human happenings. So, whether that be because of a particular construction which has been used to concentrate the fall of rain, or whether it’s from man-made constructions like the roof of a house, where rain is controlled via the likes of a drainpipe etc.
England in general has recently suffered one of the wettest winters we have on record, so it’s not a complete shock to the system that these sinkholes are appearing at a slightly higher rate than we recall to have experienced in the past. Not only that, the South East of England, where the majority of recent sinkhole occurrences have taken place, is built upon a large quantity of soluble chalk, making the perfect conditions for sinkholes.