Enterprise architect, solution architect, whats the difference?

I see most architecture practices have progression marked from solution Architect to enterprise architect.So what does it take to make this progression?Is it, for example, that once you have been solution architect for 'n' projects you are qualified to become enterprise architect? or is it if you have been solution architect for 'n' types of project hence you can become an enterprise architect. Or is it analogus to a caterpiller becoming a butterfly? Is there a moment of Zen, when a solution architect becomes enterprise architect? Can an enterprise architect descend to become a solution architect? Is it really a descent?
Let me attempt to answer these questions per my understanding.To me a solution architect provides a framework so that a sound solution can be designed and implemented. Since a solution typically spans multiple orgnisational entities within enterprise, the framework thus established, in a sense is valid for entire enterprise. So what value does an enterprise architect add, over and above this? An enterprise architect has to set up such a framework for entire enterprise (and not restricted to some entities within it). A solution architect has some freedom in setting a framework for his solution, based on overarching framework for enterprise. He can override enterprise wide framework, if his solution so demands, after following governance protocol. A solution architect can extend the framework and make it more granular. That is, enterprise wide framework will be more coarse grained, whereas solution level framework will be more fine grained. This solution level framework will have some reusable parts, which can be envisaged in any solution. Those should be moved to enterprise framework. Lifecycle changes happen in a solution level framework till the solution gets deployed and then the framework is frozen. Whereas an enterprise architect has to make sure his frameowrk is deployed rightly across various solutions and govern the changes or diversions from it. He also has to keep evolving organisation wide framework, all the time.
So from an Object Oriented viewpoint a Solution architect is a base class (appears counter-intuitive). An enterprise architect is a derived class. An instance of enterprise architect is also an instance of solution architect, but an instance of solution architect is not an instance of enterprise architect. Once a soluition architect develops the ability to genralize and abstract architecture concepts, he can progress to become an enterprise architect.