Local mystery: What was that big boom yesterday?

by Brent Eades

I’ve seen and received numerous reports of ‘an explosion’ heard in parts of Mississippi Mills yesterday at about 4:20 pm. Some people say that ‘the house shook’, and a commenter on Facebook thought something had hit his house.

But 24 hours later no one seems to know what it was. Local police and firefighters report no incidents, and a search of online seismic mapping tools show no detected earthquakes in the region then.

And it clearly wasn’t fireworks, or a meteor, as some folks have proposed.

My money was on a ‘frostquake,’ or cryoseism. From Wikipedia:

A cryoseism, also known as an ice quake or a frost quake, is a seismic event that may be caused by a sudden cracking action in frozen soil or rock saturated with water or ice. As water drains into the ground, it may eventually freeze and expand under colder temperatures, putting stress on its surroundings. This stress builds up until relieved explosively in the form of a cryoseism.

Initial indications may appear similar to those of an earthquake with tremors, vibrations, ground cracking and related noises, such as thundering or booming sounds.

PRECURSORS:

The ground must undergo saturation from thaw or liquid precipitation prior to an intruding cold air mass.

Most frost quakes are associated with minor snow cover on the ground without a significant amount to insulate the ground, and a rapid temperature drop from approximately freezing to near or below zero degrees Fahrenheit, which ordinarily occurred on a timescale of 16 to 48 hours.

Here’s some data I downloaded from Environment Canada showing local temperatures between midnight Saturday and midnight yesterday. There was indeed a dramatic drop in temperature, and there has been a lot of precip and little snow cover.

Problem with this theory: a Facebook commenter says that Environment Canada has discounted the event as being a frostquake. So what was it then?

If you have any ideas add them in the comments section below, or email millstonenews@gmail.com.