Boating Emergencies: Dial *16 (star 16) on your phone, or channel 16 on your marine radio.


Ancient Lake, Modern Danger

Lake Ontario, the most easterly of North America's five Great Lakes and the smallest by surface area, has a rippled surface that gives off a diamond-like glitter on sunny days.

It's a quality peculiar to this lake. The native Iroquois people saw it a thousand years ago when they gathered on its pebbly shores during the summer months for recreation, as did their ancestors, ten thousand years before them, who migrated from the south in the wake of retreating glaciers after the last ice age. They named the lake “Ontario”. The word, thought to derive from the Huron tongue, means “Lake of Shining Waters” This proglacial lake was created by the retreat of the middle Wisconsin glacier as it melted after the last ice age, which extended from approximately 85,000 to 11,000 year ago. The weight and movement of the massive glacier carved a basin, which filled with water as ice still blocked the present-day drainage path east to the Atlantic Ocean through the St. Lawrence Valley. The only outlet for this lake was at Rome and Utica in New York. The water exited there to the Atlantic Ocean through the Mohawk and Hudson River Valley.

When the glacier had retreated north, scientists referred to this original lake as Lake Lundy. After the waters of Lake Lundy fell due to the rise of the land, it became a smaller lake now known to scientists as Lake Iroquois. The shoreline of Lake Iroquois has been carbon dated at approximately 12,000 years old. Once the giant Wisconsin glacier retreated north of the St. Lawrence Valley, the lake's current drainage passage through the St. Lawrence River to the Atlantic Ocean opened up, and the lake's water fell to sea level.

Toronto now lords over this ancient lake, a sprawling modern city of glass and steel whose skyline is punctuated by the familiar CN Tower, the tallest freestanding structure in the Western Hemisphere. The city's harbour is insulated from the cold open lake by a sandy island complex, which has a mini amusement park and petting zoo at one end, and a busy executive airport at the other. The Toronto islands were created by sand and other alluvial material from the eroding Scarborough bluffs, which was washed westward and deposited in its current location over the centuries by the lake's strong currents.

As today's boaters and swimmers reflect on this history of Lake Ontario, we would like to remind them that the waters are very cold. Cold enough to kill. This is why we strongly encourage everyone to wear a life jacket while enjoying the beauty of the waters they plan to enjoy.

We also remind our readers that the lakes waters can rise causing hidden dangers, as happened in the summer of 2017. Looking at the photo of the pier below the surface is a warning for sailors and power boaters alike.


  • Alluvial material: typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel.
  • Glacier: A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation over many years, often centuries.
  • Iroquois: also known as the Haudenosaunee (or “people of the longhouse” are members of a confederacy of Aboriginal nations in northeastern North America. Originally a confederacy of five nations inhabiting the northern part of New York State, the Iroquois consisted of the Seneca, Cayuga, Oneida, Onondaga and Mohawk. When the Tuscarora joined the confederacy early in the 18th century, it became known as the “Six Nations.”
  • Proglacial Lake: In geology, a proglacial lake is a lake formed either by the damming action of a “moraine” (or ice dam) during the retreat of a melting glacier, or by melt-water trapped against an ice sheet due to isostatic depression of the crust around the ice.

Quick Facts

  • Lake Ontario is the 14th largest lake in the world and has a shoreline 712 miles (or 1146 kilometers) long.
  • Lake Ontario is situated at an elevation of 246 feet (or 75 meters) above sea level.
  • Lake Ontario stretches 193 miles (or 311 kilometers) in length, and 53 miles (or 85 kilometers) in breadth
  • The average depth of Lake Ontario is 283 feet (or 86 meters), with a maximum depth of 802 feet (or 244 meters).
  • Lake Ontario is named for the Iroquois word “ontara” which means "lake," with “Ontario” translated as "beautiful lake.”
  • Provides drinking water for the 2.5 million residents of Toronto, the capital city of the province of Ontario, and Canada's most-populated city.

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