Why is only one of the lone pairs on the oxygen in furan delocalized?

[![furan](https://i.stack.imgur.com/CdaJ8.png)](https://i.stack.imgur.com/CdaJ8.png)


Both the lone pairs on the oxygen are in allylic positions, thus both should be able to participate in resonance. If both lone pairs can participate in resonance, why is only one of the lone pairs delocalized? 


Also, for a lone pair to participate resonance, does it have to be in an unhybridized p orbital? If so that would explain why only one of the lone pairs is delocalized as one of the lone pairs would be in an unhybridized p orbital to make it sp2 for oxygen.


