Original: From December 7 , 1989 , to January 6 , 1990 , and from November 5 , 1990 , to February 14 , 1991 , the mountain erupted with sometimes huge clouds of ash .
Simplified: From December 7 , 1989 to January 6 , 1990 , and from November 5 , 1990 to February 14 , 1991 , the volcano erupted with sometimes huge clouds of ash .