To follow up from the post below, I went a step further to discover more about these mysterious holes that are found around the world. Through a short research stint, I've found these holes are called sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, these are a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water. Sinkholes may vary in size from less than a meter to several hundred meters both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. They may be formed gradually or suddenly, and are found worldwide. These terms are often used interchangeably though many will distinguish between those features into which a surface stream flows and those which have no such input. Only the former would be described as sinks, swallow holes or swallets.Sinkholes have also been used for centuries as disposal sites for various forms of waste. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas. In contrast, the Maya civilization sometimes used sinkholes in the Yucatán Peninsula (known as cenotes) as places to deposit precious items and sacrifices.
Thoughts: Through examining the forming of sinkholes, I now have a better understanding of why and how it is former. It is also amazing to know that these holes have put into use by as disposal sites or even act as kind of a 'safe' in the Maya civilization. However, with more human-induced into the environment, we are actually creating these to endanger ourselves. Cities could well be disappearing because of the dangers of sinkholes.
