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Features of the Oak Ridges Moraine

How was the Oak Ridges Moraine formed?

Imagine standing on your front lawn and staring up at a wall of ice a mile high. Seems incredible doesn't it, but less than a million years ago glaciers about that deep covered this part of Ontario. In fact, in this area of the Province two huge rivers of ice, one from the north and the other from the south met.

When the glaciers started to melt and the ice left the area some 10,000 years ago, the glacial debris frozen within the glaciers or pushed together between the glaciers was left behind.

The rolling hills, and the kettle lakes of the Oak Ridges Moraine, are today's surface reminders of our glacial history.

What is the Oak Ridges Moraine and where is it?

The Oak Ridges Moraine (ORM) is a prominent ridge of land formed by glacial sediments, including gravel, sand and glacial till. It is one of the most complex and largest glacial remnants in Ontario.

Rising in the Region of Peel and Counties of Dufferin and Simcoe in the west and running in a generally east-west direction for +/- 160 km into Northumberland County, the Moraine forms the drainage divide between Lakes Simcoe and Ontario and acts as the headwaters for over 35 rivers and streams in the Greater Toronto Area (GTA). Among these stream systems are the Rouge, Don, Humber and Ganaraska Rivers flowing into Lake Ontario and the Black, Holland and Uxbridge and Pefferlaw Brooks flowing into Lake Simcoe.

The GTA portion of the Moraine stretches a distance of some 90 kilometres (56 miles) and covers over 1,250 square kilometres (480 sq. miles) of the area. 8 of the 9 area municipalities in York Region have some part of the Moraine in within its boundaries. Approximately 33% of the total land area of the Region of York is within the Moraine, with the municipal percentages ranging from approximately 3% of the Town of Markham in the Moraine to approximately 82% of the Town of Whitchurch-Stouffville.

The Moraine varies in width from approximately three kilometres (two miles) at its narrowest point near Lake Scugog, to approximately 24 kilometres (14 miles) at its widest point in York Region.

What kinds of landscapes are associated with the Moraine?

There are a variety of landscapes associated with the Moraine and with our glacial history. Some of the most recognizable of these features in York are:

Why is the Moraine important?

The Oak Ridges Moraine is important for a number of reasons including: