Definition: An oceanic island, often having a characteristic ring-like shape surrounding a lagoon. Atolls are formed when coral reef grows around a volcanic island that later subsides into the ocean.
Definition: A landform consisting of loose rock particles such as sand, gravel, shingle, pebbles, cobble, or even shell fragments along the shoreline of a body of water.
Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
Definition: A tract of alluvium formed at the mouth of a river where the deposition ofsome of its load exceeds its rate of removal, crossed by the divergent channels (distributaries) of the river.
Definition: A submergent coastal landform that forms where sea levels rise relative to the land either as a result of eustatic sea level change; where the global sea levels rise or isostatic sea level change; where the land sinks. When this happens valleys which were previously at sea level become submerged.