Big volcanoes can put on quite a show, from giant mushroom clouds to thunder and lightning.

Sounds a bit frightening, but some also have a whimsical side: They can make smoke rings/! Well, fog rings.

The same kind of fog you can make by exhaling on a cold winter day. And according to physics, that makes you and a volcano a little less different than you might imagine. [intro jingle] Fog and smoke rings are both types of vortex rings. And vortices are /everywhere/.

They occur any time something drags on a fluid. The drag forces the fluid to move sideways and forward and backward, all at the same time. And that makes the fluid start to swirl. ~ And Boom.

Vortex. And vortices are literally all around you: even air/ which physicists consider a fluid, whirls into a vortex whenever you move part of your body. You can’t see them, but I’m totally vortexing it up right now!

The same sort of swirling happens when fluid bursts out of an opening, like your mouth. The sides of the opening slow the fluid down, and a vortex forms along the opening’s edge: That’s how you get a vortex /ring/. Part of the trick to making a good fog ring in the winter is to keep your mouth still and puff the air out all at once.

If it escapes quickly and smoothly, there’s a big speed difference between the air that slows around your lips and the air that shoots out the middle. That creates more drag and more swirling, so you have a better chance of seeing a ring as the water vapor in your breath condenses into fog. ~

Now, all that careful breathing might seem pretty far removed from the chaos of an eruption. But if the same phenomenon happens in two different places, scientists can place a pretty safe bet that there might be a similar cause behind both.

And recently, one team studying volcanic vortex rings published some simulations that showed this intuition is true /here, as well. Magma inside a volcano can hold trapped gas, including water vapor. ~ And in general, lots of trapped gas means more violent eruptions once the gas explosively escapes at the surface. But sometimes the magma moves into a side vent slowly enough that its gasses leak out gradually. ~ This often produces clouds around the volcano when the water vapor that used to be inside the magma condenses after it hits the outside air. ~ But the team’s simulations showed that if some rock blocks the exit, the pressure can build until that block breaks apart, and a /burst/ of gas escapes all at once.

And just like air leaving your mouth, the edge of the new hole drags some gas backward. The gas swirls, and, after condensation, there’s a visible ring. And on top of just being /neat/, studying these fog rings might give volcanologists a sense of a volcano’s underground structure, including where weaker or stronger rock might be.~ ~ But even if it doesn’t, this research shows us that anyone who can make a fog ring in winter is a little bit volcanic.

Thank you for watching this episode of SciShow. And If you like looking at fancy science rings, you might get a kick out of a few pages in our 2024 calendar. Because after more than one year of service, the James Webb Space Telescope has managed to image a bunch of space /rings/.

I mean just Take a look at these beauties around the star Fomalhaut – you’re looking at the first asteroid belt ever observed around another star! And JWST discovered there was more than one of them! Head on over to dftba.com/SciShow to order yours, today! [♪ outro ♪ ]