Photo: Jon Thorpe

Anne Bright awoke at 1:34 a.m. on Monday to what she thought was thunder.

Then she felt the entirety of her downtown Squamish home shake, and realized this was not a routine rainstorm. The window panes were rattling, reverberating with the sound.

"It was the loudest crash — it sounds almost like a train shunting, and then you hear repetitive things afterward," Bright said.

"There were a couple of loud crashes — not as loud as the first one — and then afterward you could just hear rumbling."

When she went outside and saw her neighbours looking at the Stawamus Chief, she realized that for the fourth time, a major rockfall had occurred on the monolith. Including a fall on Slhanay, this marks the fifth major rockfall event in Squamish this year.

Seismic readings from the Incorporated Research Institutions for Seismology show that a station at Watts Point registered the earth-shaking event at the popular climbing area.

The chart shows a hefty spike at the time of the rockfall, showing the incident was large enough to make the ground tremble.

There was no actual earthquake, however, as Earthquakes Canada did not register such an event.

The people who felt and heard the fall say that noise persisted beyond the initial crash. Bright said she heard sounds coming from the Chief for about 20 minutes.

Steve Quane, head geologist at the Sea to Sky Fire and Ice Aspiring Geopark, said the most likely cause of the event was recent rainfall coupled with extreme heat that occurred this summer.

The heatwave likely caused the rock to expand during hot cycles and contract in cooler temperatures. This would create stress fractures. On top of that, a recent deluge of rain would be the final trigger that set the fall in motion.

Quane added that this is happening more often now, most likely as a result of climate change.

As of Sept. 20, BC Parks has shut down a number of climbing areas in the North Walls. This order adds to closures where the Grand Wall meets the Western Dihedrals, and their respective bouldering areas, which is where the first three rockfalls this year occurred.

The Ministry of the Environment said that no one was injured in the rockfall, and geotechnical engineers will be investigating the matter.

In the meantime, the ministry said existing closures are expected to remain in effect throughout the winter, as the areas are susceptible to more rockfall.

A second rockfall Sept. 20 occurred near Angels Crest Trail about 4:45 p.m.

There were no reports of injuries from the second slide.

“We ask people to stay away from the area until BC Parks can assess the situation and until they deem okay to return,” said Cpl. Dallas Langley of the Squamish RCMP in a news release. “While this area is popular for recreation enthusiasts, we need to make sure people stay safe.”