Simplify the following text for a Grade 8 native English-speaking person.
Original: Other major twentieth century eruptions occurred in 1949 , 1971 , 1983 and 1992 , as well as the 2001 eruption .
Simplified: Other major 20th-century eruptions occurred in 1949 , 1971 , 1981 , 1983 and 1991 â `` 1993 .