Complex sentence: He attended a technical high school and honed his youthful interest in geology by taking part in several Soviet geological expeditions after his high school graduation in the early 1930s, expeditions which took him all over the Soviet Union.
Split into simpler sentences: He attended a technical high school and honed his youthful interest in geology by taking part in several Soviet geological expeditions after his high school graduation in the early 1930s. These expeditions which took him all over the Soviet Union.