A- Atoll --- A type of small island
B- Archipelago --- An island chain
C- Gondwana --- A supercontinent
D- Icon --- Something with symbolic meaning
Explanation:
A- An atoll is a coral island or an archipelago that looks like a continuous or torn ring surrounding a lagoon. More precisely, the atoll is an elevation at the bottom of the ocean, crowned with a coral superstructure, forming a reef with a group of islands separated by straits. These straits connect the ocean to the lagoon. If there are no straits, then the land forms a continuous ring, in this case the water in the lagoon may be less salty than in the ocean. The elevation at the bottom of the ocean usually takes the form of a cone formed by an extinct volcano.
B- An archipelago is a group of islands located close to each other. As a rule, islands in the archipelago have the same origin (mainland, volcanic, coral) and a similar geological structure.
C- Gondwana was an ancient supercontinent in the southern hemisphere, including Africa, South America, Antarctica, Australia, New Zealand, as well as Arabia, Madagascar and India. It was formed at the end of Precambrian (750-530 million years ago) as a result of the split of the supercontinent Rodinia.
D- In religion, an icon is a sacred image of persons or events in biblical or church history.
