。
My father made a long tear there.
Literal
Father [topic-は] there [at-で] long tear [object-を] made.
裂け目 is a compound noun: 裂ける (to tear/split) + 目 (spot/opening) = 'a tear/crack.' そこで can mean 'there' (location) or 'at that point' (narrative). A somewhat odd sentence out of context.