Answer: <em>I think </em><u>Southeast</u>
Explanation: The north american continent is moving southeast 
 
        
             
        
        
        
Separation by density is the answer
        
                    
             
        
        
        
I would say that the resource you could use to find the meaning of <em>ambiguous </em>is the dictionary. 
An almanac is an annual publication about weather, crops, etc.
A thesaurus is a dictionary of synonyms.
An encyclopedia is self-explanatory.
        
             
        
        
        
Salt water makes up 97 percent of the earth's waters as 3 percent is only fresh water.