If you were to mix a very large amount of francium or rubidium with water, what would the crater be like?

Question: If you were to mix a very large amount of francium or rubidium with water, what would the crater be like?
- Keywords:
  crater,
  francium,
  reaction,
  rubidium,
  water
Asked by jamesat79 to Jess on 28 Jun 2013.
- Jess Bean answered on 28 Jun 2013:
  
  The problem with things like francium is that once you get to atoms that bag they become really radioactive! The atoms are so radioactive that the heat produced by them will make the entire sample evaporate!
  With rubidium the reaction with water would be pretty big!

Question: If you were to mix a very large amount of francium or rubidium with water, what would the crater be like?