Complex sentence: Hainan Island has a complex tectonic evolution history in which it has experienced multi-stages of metamorphism, volcanic and intrusive activities, tectonic drifting, etc. Its Precambrian rock unit was not widely exposed, but mostly found in Western part of the Island.
Split into simpler sentences: Hainan Island has a complex geological history in which it has experienced multi-stages of metamorphism, volcanic and intrusive activities, tectonic drifting and more. The oldest rocks are not widely exposed, but mostly found in Western part of the Island.