Shake, Rattle and Roll: Earthquakes in Canada

People often ask if we have earthquakes in Ontario.
The answer is yes, we do experience earthquakes, but they are small in size and are uncommon in comparison to the east and west coasts of North America, where “big ones” have happened.
So, what causes an earthquake and why do we only have small ones in Ontario? As we know, during an earthquake, the ground shakes. That shaking results from the sudden release of force and energy that built up within the rocks over time. The sudden jolt causes the rocks to break and slip past each other and that makes the ground vibrate. These zones of broken rock are called faults. Around the world, earthquakes are caused by the shifting of large slabs of the Earth called tectonic plates — a lot like blocks of ice on the great northern rivers or lakes during spring breakup.
For example, most earthquakes along the West Coast of North America are generally associated with huge faults that occur where tectonic plates slide along, or below, each other. One famous example is the San Andreas fault in California.
Fortunately, we don’t have these types of faults in Ontario. The ancient and generally stable Precambrian Shield rocks that are one to three billion years old are what lie beneath the ground in our province. These old rocks, which are normally quiet with respect to big earthquakes, make up the Canadian Shield. So, we don’t expect to experience a major earthquake in Ontario any time soon.
However, there have been small earthquakes in southern Ontario and in some parts of northern Ontario. In southern Ontario, there are a number of weak earthquakes, which appear to be related to ancient faults that cross or run along the St. Lawrence River and Lake Ontario.
These ancient faults are thought to mark the boundaries between, or occur within, ancient tectonic plates.
Another area of active earthquakes is located in western Quebec, east of Lake Timiskaming and the Ottawa River. This zone is the source of earthquakes that can be felt in Sudbury, Toronto, and sometimes Sault Ste. Marie and Timmins. On June 23, 2010, I felt a moderately strong earthquake that occurred in that zone as I sat in my office in Sudbury.
In the Far North of Ontario, there are very few earthquakes and the ones that do occur are very small and generally not felt. That’s because of the strong, stable Canadian Shield rocks in this area. The cause of these weak earthquakes is not related to boundaries between tectonic zones. These small earthquakes may happen because the land is slowly rising along the shores of Hudson Bay and James Bay. (Editor’s note: Fyon expanded on this in the July 18, 2013 of Wawatay News.)
Around the world, when a major earthquake takes place under water, it is possible that a tsunami may form. You may remember March 11, 2011, when parts of Japan were destroyed by a tsunami created by an earthquake. Luckily, this is not likely in Ontario because our earthquakes are generally small and weak.
There have been some rare experiences where an earthquake under or near Lake Ontario has resulted in high waves and flooding.
On April 25, 1854, the shoreline of Lake Ontario at Niagara-on-the-Lake grew by about 150 metres and a series of waves up to two metres high flooded docks and property. This event is believed to have been the result of an earthquake that happened on the bottom of the lake.
Records of similar events have also been documented in 1847, 1853, 1895, 1923, and 1940 — surfing anyone? It would be interesting to know if there is traditional knowledge about similar events along Hudson Bay.
So, for you Elvis Presley fans, the next time you listen to the Elvis song “Shake, Rattle and Roll,” remember the lyrics: “I went over the hill, way down underneath”. Maybe, just maybe, Elvis was speaking about an earthquake that took place “way down underneath” – just like the Ontario beneath your feet.
To learn more about historical earthquakes that have taken place in and around Ontario you can visit Natural Resources Canada online at: http://www.earthquakescanada.nrcan.gc.ca or follow @CANADAquakes on Twitter.
Andy Fyon is the director of Ministry of Development and Mines’ Ontario Geological Survey. For more information about the geology of Ontario: http://www.mndm.gov.on.ca/en/mines-and-minerals/geology