Answer: Foreshadowing
Explanation:
Foreshadowing simply refers to an indication or a warning of an event that will occur in the future. It is a literary device whereby the reader is given an hint of what will happen next in a particular story.
Foreshadowing is used to create suspense because when it's used, the reader will be curious to know what happens next. In this story, the chestnut tree split by lightening upon Jane and Rochester’s engagement simply gives an hint that Jane and Rochester would eventually split.
