How the Oak Ridges Moraine was formed

Summary

The transcript details the formation of the Oak Ridges Moraine over the last two million years during repeated ice ages, particularly the Wisconsin glaciation. As glaciers melted, they created channels that deposited sediments, forming a continuous ridge extending 160 kilometers. The area, once dominated by glacial lakes, transformed over time into a diverse ecosystem with tundra vegetation giving way to coniferous forests and eventually deciduous trees like oaks and maples. This landscape supported both wildlife and the nomadic tribes of Ontario's first people, shaping the environment that European settlers encountered over 400 years ago.

Takeaways

• ❄️ The last two million years have seen Canada and the northern US undergo an ice age with glaciers advancing and retreating.
• 🏔️ The Wisconsin glaciation was the last major ice advance, covering most of Canada and parts of the northern US, with ice thickness reaching over two kilometers in some areas.
• 🌊 As glaciers retreated, they formed two lobes that created a distinct crack along the future ridge line of the Oak Ridges Moraine.
• 💧 Torrential flood channels developed beneath melting ice, carrying sediments and creating the initial core of the moraine.
• 🌄 These flood channels are now represented by the valley systems of the Holland River, Black River, and Pefferlaw Brook.
• 🛤️ Water collected in troughs held by ice slopes and the Niagara Escarpment before draining south and southwest along meltwater channels.
• 🏞️ The retreating ice left behind a giant accumulation of tills and stratified materials, forming a continuous ridge about 160 kilometers long.
• 🗺️ The Oak Ridges Moraine, rising over 300 meters above Lake Ontario, remains a prominent landform in southern Ontario even after the ice sheets retreated.
• 🌱 By 9,000 years ago, tundra vegetation gave way to coniferous forests, which later transformed into oak and maple forests.
• 👥 The landscape that developed supported wildlife and nomadic tribes, and it was the same landscape encountered by the first European settlers over 400 years ago.

Q & A

What significant climatic period affected Canada and the northern US in the last two million years?

The last two million years were marked by an ice age characterized by glaciers continually advancing and retreating across the landscape.

What was the Wisconsin glaciation?

The Wisconsin glaciation was the last major ice advance that covered most of Canada and parts of the northern US, with ice thickness reaching over two kilometers in some areas.

How did the Oak Ridges Moraine form?

As glaciers began to retreat and melt, they divided into two lobes, creating a crack that allowed torrential flood channels to develop beneath the ice, carrying sediments and forming the initial core of the Oak Ridges Moraine.

What geological features can be seen today as a result of the melting ice?

The well-defined valley systems of the Holland River, Black River, and Pefferlaw Brook are remnants of the flood channels created during the melting of the ice.

What role did the Niagara Escarpment play during the ice age?

The Niagara Escarpment acted as a highland that helped hold water in troughs formed by the ice, which eventually drained away along meltwater channels.

What were the large glacial lakes that formed as a result of the melting ice?

The melting ice led to the formation of large glacial lakes, including Lake Iroquois, where present-day Ontario is located, and Lake Algonquin, which covered areas of the future Great Lakes Huron and Michigan.

How thick is the Oak Ridges Moraine today?

The Oak Ridges Moraine remains a prominent landform in southern Ontario, up to 200 meters thick and rising over 300 meters above Lake Ontario.

What type of vegetation returned to the Oak Ridges Moraine after the ice retreated?

After the ice retreated, small hardy tundra vegetation initially returned, which was soon replaced by coniferous forests consisting of spruce, fir, and pine species.

What kind of forest dominated the Oak Ridges Moraine 6,000 years ago?

By 6,000 years ago, the Oak Ridges Moraine was dominated by towering oaks and maples, supporting various wildlife species and the nomadic tribes of Ontario's first people.

How did the landscape of the Oak Ridges Moraine greet the first European settlers?

The landscape that greeted the first European settlers just over 400 years ago was characterized by the diverse ecosystems supported by the towering trees and rich wildlife of the Oak Ridges Moraine.