Answer: a crack forms in the oceanic crust
Explanation:
 
        
                    
             
        
        
        
I believe the first one is 'physical geography' :-)
        
             
        
        
        
I’m not sure exactly what you’re looking for, but the US spent $15m dollars and gained 54% of Mexico’s pre-1836 territory. There’s a nice article on Wikipedia called ‘Mexican Cession’ that seems helpful. Hope this is helpful :)