Heat might have played a part in B.C. rockfall

Numerous rock climbing routes on the renowned Grand Wall of the Stawamus Chief in Squamish, B.C., are closed after a large slab broke off.

The society that supports rock climbing in the area says hot weather might be to blame.

BC Parks confirms the rockfall happened early Tuesday morning in the provincial park and a geotechnical assessment is underway.

A statement from the Ministry of Environment and Climate Change Strategy says numerous climbing and bouldering routes have been closed because the rockfall was much larger than others that have occurred recently along the face of the roughly 600-metre high granite dome.

Social media posts by the Squamish Access Society report a series of rockfalls began late last month as much of B.C. was sweltering under temperatures that broke 40 C in several regions, including Squamish.

The society says studies done in Yosemite National Park in California show that water seeping into fractures running behind and parallel to a sheer rock face can be just as damaging during extreme heat as they are in winter, when the freeze-thaw cycle can pry sheets of rock from the mountainside.

Rocks falling from the crags of the Stawamus Chief are common, but the society says what happened Tuesday caused "catastrophic damage" to the Grand Wall and Grand Wall Boulders, which attract climbers from around the world.

"There remains significant risk of further rockfall and there are a number of downed trees in the Grand Wall Boulders," the site says.

It says everyone should stay out of the entire area because of the frequency of rocks falling over the last month.