Laurentian River System
The Southern Laurentian Channel is an ancient underground river in southern Ontario, Canada.<ref> Template:Cite news </ref><ref> Template:Cite news </ref><ref> Template:Cite news </ref><ref> Template:Cite news </ref> The river predates the recent ice ages.<ref name=OakRidges2014-08-04/> The river valley was filled with glacial debris. Water still flows down this old valley—underground. The source of the aquifer is the Georgian Bay,<ref name=":0">Template:Cite book</ref> approximately Template:Convert away.
In 2003 it was discovered that the southern section of the Laurentian aquifer reaches under High Park in Toronto, Ontario, Canada.<ref name=":0" /> This is believed to be where the Laurentian River System drains into Lake Ontario. An overflow pipe is visible running into Spring Creek in High Park and is always at a steady flow. Its current purpose is to enrich local coldwater wildlife in the creek and relieve hydrostatic pressure. The area surrounding the outlet is stained red indicating a high iron content. The water flowing from it is naturally pure and cool, at around 6-9 degrees Celsius or 42-48 degrees Fahrenheit.
During the discovery of the Laurentian Channel, a well was drilled to investigate further. While it was being drilled, a massive burst of water, silt and gravel suddenly rocketed out of the well. Somehow, the Laurentian Channel's flow to Lake Ontario had been blocked, causing a huge pressure buildup.
The bedrock under Toronto has several dips believed to be carved by the Laurentian River.<ref name=GeologyToronto1980/>
The Laurentian Channel, 25–30 km wide in some areas, 100 km long, and greater than 100 m deep, still lacks data regarding its total size and sediments, relying on well sites for information. Sediments in the channel range from sands and gravels near the bottom and clay-like silts near the top.<ref>Template:Cite journal</ref>