If you could slice open the Moraine from end to end, you would see three main sand-and-gravel layers separated by clay and tills – something like a triple-Decker sandwich – situated at different depths below ground surface. Of these three layers, the middle layer, referred to as the Oak Ridges Moraine aquifer complex, is the largest and the most extensive. The movement of precipitation and melt water below the surface of the ground is highly complex and difficult to map.The Moraine is composed primarily of sands and gravels, which are much more porous than silts or clay. Because of this 80% of surface water on the moraine sinks down through these sands and gravels to the aquifers below.
Aquifer complex- a system of natural reservoirs that receives and the stores infiltrating water, which is filtered and cleansed on its downward path.
Water discharges from the ground along the Moraine, seeping into marshy wetlands, springs and intermittent streams that start off as thin ribbon of water and end up as a full-blown river.