The freezing and melting of Canada's lakes and rivers are a beautiful but sometimes dangerous consequence of our four-season weather.

Johanna Wagstaffe explains how a potentially dangerous ice jam is made — and why it's important to know how they are made — all in this week's Science Smart video, in the player above.

If you have a science question you'd like answered, send Johanna a tweet (@Jwagstaffe) or an email: johanna.wagstaffe@cbc.ca.