The Oak Ridges Moraine is a geographic area in southern Ontario, Canada stretching from Milton to Rice Lake, near Peterborough. The Oak Ridges Moraine is one of the most significant landforms in southern Ontario. The moraine gets its name from its rolling hills and river valleys extending 160 km from the Niagara Escarpment to Rice Lake. It was formed 12,000 years ago by advancing and retreating glaciers.

The moraine contains the headwaters of 65 rivers and streams. It has a wide diversity of woodlands, wetlands, watercourses, kettle lakes, kettle bogs and significant flora and fauna. It is one of the few remaining continuous green corridors in southern Ontario: it remains 30 per cent forested and is one of the last refuges for forest birds in all of southern Ontario.

The moraine's sands and gravel deposits act like a giant rain barrel storing rain and snow melt. This underground water is then filtered through layers of sand and gravel (aquifers) and slowly released as cool fresh water to the rivers and streams flowing north into Lakes Simcoe and Scugog and south into Lake Ontario. The greatest threat to the function of the moraine is land development on and below its surface, particularly in the headwater areas.

Use of the moraine is currently under dispute; environmental groups such as the Sierra Club maintain the area's delicate ecosystem is threatened by development. Attractive forests and hilly relief typical of the moraine are a magnet for developers looking for building opportunities near the densely populated greater Toronto area. However, many planners and residents see a need to preserve it from the negative aspects of urban sprawl. Recent legislation has provided a means of preserving the moraine.

The Wisconsin glaciation's retreat, during the most recent ice age, created the moraine. As glaciers grow they pick up large amounts of soil, gravel and boulders. As the glaciers melt the rocks and soil they contain get washed away. The Wisconsin glacier retreated in more or less the direction of the moraine. As the glacier melted it split into two lobes, which lay north and south of the current location of the moraine. Rocks and soil released by the melting of these lobes was washed into the gap between them, laying down the material that now forms the moraine. .

External Links

• Government of Ontario - Ministry of Municipal Affairs and Housing: The Oak Ridges Moraine
• Natural Resources Canada - Earth Sciences Sector: Oak Ridges Moraine Groundwater Research
• Natural Resources Canada: Oak Ridges Moraine - A Ridge of Resources