What is a sinkhole? How to teach about the formation of sinkholes

The idea of the ground literally opening up under your feet, without any warning, is the stuff of nightmares or fantasy novels. But sinkholes are a very real issue occurring across the globe – they can appear anywhere at any time and cause widespread havoc and chaos to everyday lives. This article looks at how to teach about the formation of sinkholes and how to engage students about this fascinating and terrifying natural phenomenon.

Engaging your students about the causes of sinkholes

Sinkholes offer the opportunity to cover a wide variety of subjects in school or university, including geology, earth science, geography and history. The shocking visual impact of a sinkhole ensures that children of all ages will be captivated by this incredible phenomenon.

A powerful way to start your lesson or lecture is to give visual examples of the devastating impact that sinkholes can have on our daily lives. BBC Active Video for Learning has distributed a fascinating and thrilling educational science programme, Swallowed by a Sinkhole (Horizon). This programme examines what happened in Tampa, Florida when local resident Jeff Bush was swallowed by a sinkhole without any warning. He and his entire bedroom disappeared and his body was never recovered.

This sets the scene for the programme to consider how sinkholes are formed, delving deep into the earth’s history for answers. The programme also asks a compelling question which is highly relevant to all of us across the globe – are we likely to see more and more sinkholes appearing on our planet, and what does this mean for us? Using powerful video and visual images to convey the terrifying reality of a sinkhole will ensure that your students are captivated and eager to learn more.

What are sinkholes and how do they form?

A sinkhole is the name for a hole in the ground which is created when a layer of rock underneath the ground is dissolved and eroded by acidic water. Sinkholes mainly happen in areas of “karst” terrain, where soluble bedrock such as limestone can be dissolved by water. Once the rock is fully eroded it creates a cavity below the surface, and the top levels of ground soil can collapse into the cavity when the weight above becomes too heavy.

Sinkholes can vary enormously in size – some are only a few feet across and some, such as the devastating sinkhole in Florida, are large enough to swallow rooms, cars and buildings. Long periods of intense rainfall or poor drainage can make areas more susceptible to sinkholes. There can be some warning signs of potential sinkholes in populated and urban areas – sometimes cracks can appear in the foundations of houses or doors and windows may not close properly. Sinkholes often, however, appear without any warning at all which is why they are a particularly shocking natural phenomenon.

Sinkholes around the world

Sinkholes are appearing without warning in every corner of the globe. Some of the most infamous and terrifying examples include a 65-foot-wide and 100-foot-deep sinkhole in Guatemala City, which swallowed an entire 3-storey factory and killed 15 people. In China’s Chongqing District, the deepest sinkhole in history was recorded at 662m deep and 626m wide. Other significant sinkholes have been noted in Bolivia, Croatia and in the UK.

In the county of Hertfordshire, UK, there have been two incidents of sinkholes during the last year. In 2014, a 35-foot-wide and 20-foot-deep sinkhole opened up in a residential road in the town of Hemel Hempstead, resulting in the evacuation of 17 nearby homes. Recently in St Albans, local residents were stunned to be woken in the early hours of the morning by the sound of a crash to see a 20-metre-wide hole had appeared in their road. There had been possible warning signs the week before, when a local postman injured himself on a drain cover that gave way. One of the local residents speaks about their experience:

“We live close to the sinkhole and we’re lucky that we can stay in our home. After the collapse, we went away for 5 nights, staying with friends and in local hotels. It was important for us to be at home because we have our things to hand so we could carry on with our lives as normally as possible. Moving musical instruments, swimming kits and text books for 3 children to a hotel seemed really unattractive! Our local friends have been really supportive in many ways; inviting us for meals, taking our laundry and giving us a parking space on their driveway. It’s been an unsettling time but we’ve managed to carry on going to work and school as usual. I think that’s helped us cope well together as a family so far.”

Sinkholes are a global issue that affect homes and families across the world. With more and more examples available of the impact that sinkholes have on our lives, students will be fascinated to learn more about their formation.

BBC Active Video for Learning offers thousands of high quality BBC educational programmes covering a wide range of topics. These powerful educational resources will enrich your next class or lecture and are perfect for bringing any topic to life.