It's Just so Basic

pH Scale DiagrampH Scale DiagramThe snakes have not chosen to make Manitoba their home because of the limestone ground; however, the fact that the ground is made of limestone is a very important part of the puzzle. These snakes spend the winters in dens, so what geologic forces created the dens that we see today? To understand this, it is necessary to take a short chemistry lesson.

Illustration of acidic rain dissolving limestone rock in the groundIllustration of acidic rain dissolving limestone rock in the groundPH is the measure of how acidic or basic a particular chemical or compound is. Acidity or alkalinity (base) is determined by measuring the activity of hydrogen ions within the subject. The more hydrogen ions a compound has, the lower the pH will be, and the lower the number of hydrogen ions, the higher the pH will be. The pH scale measures from zero to 14. A pH of zero to seven means the compound is acidic, while eight to 14 is basic. A pH of seven means that it is neutral, like distilled water. When an acid and a base come into contact with one another, they tend to neutralize each other as their combined pH gets closer to seven. As we learned earlier, limestone is formed from calcium carbonate which is quite basic on the pH scale. Conversely, rainwater has a lower pH, meaning that it falls into the acidic category of the pH scale. This means that when rainwater falls from the sky onto the limestone, the two react with one another and the alkaline limestone is slowly eaten away by the more acidic rainwater as it seeps into the ground. In Manitoba, near the area of the Narcisse Snake Dens, the rainwater was doing just that to the limestone ground. As the rainwater would enter the limestone it would create underground rivers, channels and huge caverns that were not visible from the surface of the ground. The rainwater was essentially slowly eating the limestone from the inside out. Underneath the ground, large caves much like Carlsbad Caverns in New Mexico were being created.

boardwalkIllustration of acidic rain creating caves within limestoneWinters in Manitoba are very cold, with temperatures often dipping down to minus 50 degrees. The limestone rock is subjected to these freezing temperatures year after year, and the freezing and thawing of water that can accumulate within the cracks and caverns in the limestone significantly weaken these areas. Over time, many of these underground caverns have weakened to the point of collapse, causing large sinkholes. There are many of these sinkholes throughout the Narcisse area, with three large ones being about as big as a living room. These sinkholes have come to be known as the Narcisse Snake Dens.