Complex sentence: In spite of harsh climatic conditions, the terrain of basaltic origin and rhyolite, is very rugged and has a succession of high plateaus and mountain ranges, and plateaus and hills of medium altitude.
Split into simpler sentences: In spite of harsh climattic conditions, the terrain is of basaltic origin and rhyolite. It is very rugged and has a succession of high plateaus and mountain ranges, and plateaus and hills of medium altitude.