• Yukon's Mount Steele, before and after the Oct. 11, 2015 landslide. (Photo: NASA Earth Observatory)

A cataclysmic landslide occurred in Canada last month — and hardly anyone noticed.

The massive October 11 slide on remote Mount Steele in Kluane National Park — equivalent to the weight of 33 million pickup trucks — would have gone undetected if scientists at Columbia University hadn't noticed that some unusual seismic activity had been reported by an unmanned monitoring station 25 km from the collapse site, reports the National Post.

The landslide was then confirmed by a NASA satellite, which zoomed in on the area and discovered an enormous debris field surrounding the mountain.

Had the 45-megaton slide occurred in a populated mountainous region, it likely would have resulted in casualties. Instead, the landslide is expected to rank among the top 10 strongest of 2015 worldwide — with no harm done.

Notable Canadian landslides

Landslides are a common occurrence in Canada - particularly in the Rockies - causing an estimated $200-400 million in damages annually, according to Natural Resources Canada. They can be triggered by earthquakes, excessive rainfall or human activity and pose a significant threat to life and property. Here are some notable landslides that have occurred in Canada in the last 120 years:

April 29, 1903: Frank, AB

Just after 4 a.m on April 29, 1903, 90 million tons of limestone rock suddenly tumbled down the side of Turtle Mountain, obliterating the eastern edge of the mining town of Frank. An estimated 90 people were killed, making it the deadliest landslide in Canadian history.

November 12, 1955: Nicolet, QC

Situated at the point where the Saint Lawrence and Nicolet rivers meet, the town of Nicolet sits on layers of sand and marine clay, making it prone to landslides. On November 12, 1955, seven acres of highly unstable clay gave way, sweeping six buildings into the Nicolet River. Three people were killed and a cathedral and trade school were destroyed.

January 9, 1965: Hope, BC

With an estimated volume of 47 million cubic meters of rock, mud and water, the Hope Slide remains the largest landslide ever recorded in Canada. Two small earthquakes were recorded in the area that day, but it’s still not clear what triggered the slide, which killed four motorists. A massive scar of bare rock can still be seen on the side of the mountain today.

August 1, 1973: Harbour Breton, NL

After weeks of heavy rain, a steep hill above the town of Harbour Breton suddenly gave way around 3 a.m. on August 1. Four houses were swept into the harbour, resulting in the death of four children. The youngest of the 14 survivors of the disaster was 21-month-old Cavell Hickey, whose crib was carried into the attic of her house by the torrent of mud and water, allowing rescuers to reach her through the roof.

January 19, 2005: North Vancouver, BC

Along with its mild climate, the beautiful ridges, creeks and forests that surround Vancouver make it one of the most desirable places to live in Canada — but the West Coast lifestyle comes with risks. Following a heavy winter rainfall in January 2005, a slope in the picturesque Berkley neighbourhood of North Vancouver gave way and crashed into a home, killing local teacher Eliza Kuttner and forcing the evacuation of several other homes. The incident sparked litigation against the city and realtors, but ultimately led to improvements in local disaster prevention policies.

Want more landslide info? Explore the Canadian Disaster Database using this interactive map from Public Safety Canada