tectonics

Short but interesting just out today (and apparently it has not been entered here yet - apologies if it has) but I have not seen it: http://www.livescience.com/28401-north-america-geology.html

I was reading that thread about plate tectonics on Mars and here's my question: On Earth, is it known if plate tectonics activities are increasing, decreasing or stable? Because, if what I read is true, that unique continent which once existed, Pangea, has broken into many pieces and formed...