How do coral reefs form? Objective Students will be able to: 1. Explain how coral reefs are formed. 2. Identify three shapes of corals. 3. Name three threats to coral reefs. Background The islands of American Samoa are blessed with an abundance of coral (over 250 species). Corals are animals like ourselves, although that may not be readily apparent because many look like rocks. In a sense, corals are indeed partly rock, because only the outer thin layer of the coral is inhabited by the coral animal itself. In that way, corals are like large trees – the inner part is hard and provides structura Duration: 60 Minutes.