Complex sentence: He published a second volume in 1887 concentrating on volcanic phenomena, which was based on expeditions to view the erupting Mauna Loa in 1859, and nearby Kīlauea and Hualālai on Hawaii island.
Split into simpler sentences: He published a second volume in 1887 concentrating on volcanic phenomena. This was based on expeditions to view the erupting Mauna Loa in 1859, and nearby Kīlauea and Hualālai on Hawaii island.