Complex sentence: The area around the Messel Pit is believed to have been geologically and tectonically active during the Eocene, leading scientists hypothesize that events much like 1986 volcanic gas releases at Lake Nyos, Africa could account for the large deposition of non-aquatic species.
Split into simpler sentences: The area around the Messel Pit is believed to have been geologically and tectonically active during the Eocene. Leading scientists hypothesize that events much like 1986 volcanic gas releases at Lake Nyos, Africa could account for the large deposition of non-aquatic species.