Bookmark this page
Provincial Links

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:

  • Kettle lakes, such as Lake Wilcox, Musselmans Lake and Hackett Lake shown in this picture
  • Hummocky terrain (also sometimes called "knob and kettle" topography) on the west side of the York-Durham line just south of Aurora Rd. in Whitchurch-Stouffville and in the north-west part of King Township
  • Glacial kames such as the large hill that Hwy. 9 bisects at Dufferin St. in King Township
  • Beach Ridges from glacial Lake Algonquin found along Hwy. 9 just west of Hwy. 400 and on Weston Rd. just south of Hwy. 9

Why is the Moraine important?

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

  • Parts of the Moraine serve as a groundwater recharge areas and other parts serve as groundwater discharge areas for approximately 65 watercourses, of which 35 are found within the Greater Toronto Area (GTA)

  • The steep slopes and poor soils for agriculture in many parts of the Moraine have resulted in the area containing the majority of the remaining natural areas in the GTA bio-region including forests, wetlands, and habitat for wildlife species
  • The public open spaces on the Moraine, including the 5,000 acres of Regional Forest tracts in York Region provide opportunities for regional scale recreation, education and nature appreciation

  • The gravel and sand of the Moraine provides aggregate materials used in construction projects within the GTA

  • The Moraine historically has accommodated towns, villages, and urban areas which provide housing and employment opportunities for many people within the Region. In many parts of York such as King Township and Whitchurch- Stouffville, agriculture is a viable and important activity