Why does the ozone layer float?

Laura - Obviously, the ozone layer is really important because it protects us from UV rays. But actually, that's one of the reasons why it actually is up there because it's continually being reformed. It needs to be up there, getting the UV rays, absorbing them, having that chemistry going on in the atmosphere. So, it is actually sort of heavier, but actually, it's because it's continually being reformed.

Dominic - I guess, another factor here is that because the ozone layer is absorbing all this ultraviolet radiation from the sun it's actually getting really quite hot. We think of temperatures decreasing with altitude, but when you get up to these quite high altitudes that air is getting hotter. Of course, hot air floats because it's less dense. That's how a hot air balloon flies. And so, this ozone is naturally quite buoyant because it's hot.