Sinkhole in Hemel Hempstead

The recent sinkholes in Hemel Hempstead left a lot of people shocked and surprised and the size of the hole, and how quickly it happened. 

The fact that it was occurring on people's driveways, alongside the motorways and nearly underneath people's houses was terrifying for some to understand.

The 15ft deep sinkhole closed the M2 motorway near Kent.

These sinkholes occur after heavy rainfall. Rainfall seeps through the soil absorbing carbon dioxide and reacts with decaying vegitation, creating a slightly acidic water. Water moves through spaces and cracks underground, slowly dissolving limestone and creating a network of cavities and voids. As limestone dissolves, the pores and cracks are enlarged and carry more acidic water. 

Sinkholes are therefore formed when land surface above collapses or sinks in to the cavities, or when surface materials is carried downward in to the voids. 

Weather

To look in to the cause of limestone and sinkholes, we have to look at our weather and why it could be the main cause of the problem.

Much of the worlds weather is determined by the movements of jet streams. Jet streams are the current of air that travels the globe at high altitude. British weather is usually determined by the streams blowing in across the Atlantic from Southern United States.

Does climate change also have a part to play?

Yes, anything that affects the amount of energy absorbed from the sun, or the amount being radiated by the Earth, that is the affect of climate change.
There are growing evidence that the warming is due to vastly increased- qualities of greenhouse gases in the atmosphere. Strongest, most important greenhouse gas is the water vapor.

What causes Sinkholes then? 

Sinkholes occur when there's a collapse caused in the surface area. Chemical dissolution of carbonate rocks or suffusion processes in sandstone. You have two types of sinkholes, artificial or natural.
Natural processes of erosion is a gradual removal of soluble bedrock by percolating water, which is the collapse of a cave roof.
Groundwater may dissolve the carbonate cement holding the sandstone particles together, which gradually forms a void.

Artificial processes are mines and salt cavern storage in salt dons. They can occur from over pumping and extracting of groundwater and subsurface fluids. 

Limestone

Myself and Ashleigh have come together and after a few hours of research, we have decided that our topic will be around limestone and the sink holes.

We will reserch what creates sinkholes and why they appear, how limestone affects it and the bedrock of Wales.

Included in the podcast will be our visit to botonocal gardens and st fagans.

We are both very excited to create a fun and creative podcast.