1004 - Under the Surface

Beneath the wooden fence in front of you lies a fissure-a large crack in the bedrock that water can pass through. Fissures are part of special landscapes known as karst topography, which contain large areas of soft rock that can dissolve in water. As parts of the bedrock dissolve, a system of sinkholes, caves, and underground water reservoirs, called aquifers, starts to form.

Much of the world’s fresh water is held in these natural aquifers. Karst aquifers, like the one here, get filled by rainwater and snowmelt that falls through the fissure and collects beneath the Earth. Since this surface water doesn’t have to pass through much sand or soil to reach the aquifer, it doesn’t have a chance to filter properly. It is then very easy for these water supplies to become polluted.