Add to ORKGIn this paper, we describe the Circumstantial Event Ontology (CEO), a newly developed ontology for calamity events that models semantic circumstantial relations between event classes, where we define circumstantial as inferred implicit causal relations. The circumstantial relations are inferred from the assertions of the event classes that involve a change to the same property of a participant. Our model captures that the change yielded by one event, explains to people the happening of the next event when observed. We describe the meta model and the contents of the ontology, the creation of a manually annotated corpus for circumstantial relations based on ECB+ and the first results on the evaluation of the ontology