1. ring-shaped coral reefs or islands that encircle a lagoon

Examples

• The Maldives consists of numerous atolls scattered across the Indian Ocean.
• Scientists study how atolls form around volcanic islands over thousands of years.
• Many Pacific atolls are threatened by rising sea levels.
• The atoll’s crystal-clear lagoon attracts divers from around the world.
• Small communities live on some of the larger atolls in the region.
• Climate change poses serious risks to low-lying atolls.