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The 3 layers of geology under the Pickering Lands

In this blog posting, I explore the geology under the Pickering Lands. Perhaps it’s not critical to know, but I like to be thorough in my quest to get to know a place, and that means going deep. Most people aren’t aware of all the history under their feet. If you are one of them, like I was, be prepared to be amazed.

There are basically three major layers under the Pickering Lands and the GTA in general. First at the bottom, is very hard rock from the Precambrian era, which is the oldest era on earth (>570 million years ago). This in itself is mind blowing. In Canada, we tend to think of everything as new, but no, we are ancient!

Next, on top of the Precambrian rock is sedimentary rock that resulted from sediment settling during the Ordovician period (505 to 438 million years ago) when this area was a tropical sea just south of the equator! This too blows my mind. Imagine how far this rock beneath us, which contains marine fossils to prove its history, has been!

Finally, on top forming the third layer is glacial till deposited by glaciers as well as sediment that settled during ice-free periods in the last 150,000 years. As glaciers came to this area, they transported a mixture of clay, silt, sand, pebbles and boulders, which is called glacial till.

Becoming aware of the underlying geology of the Pickering Lands or any land we are involved with gives us a greater appreciation of the land. It is not just “dirt and rock.” No. Any land we deal with has its own long and fascinating history that makes it uniquely what it is today and is worth discovering and aweing over.

Knowing a bit about the underlying geology also gives us a practical understanding of the land. For instance, in my last blog about my visit to Thistle Ha’ farm, I mentioned that the farmhouse was built of boulders collected from the property. These boulders are glacial till boulders!

Stay tuned for my next blog post in which I will talk in more depth about the soil of the Pickering Lands.

Disclaimer: I am not a geologist. Instead of referencing me, please go to these excellent references:

- Ontario Rocks: Three Billion Years of Environmental Change (2002) by N. Eyles

- Special Places, The Changing Ecosystems of the Toronto Region (1999) by B.I. Roots, D.A. Chant, and C.E. Heidenreich

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